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Chapter 17 questions

2007-12-06T14:39:00.001-08:00

1. List and describe the locations of the major parts of the alimentary canal.

a. Mouth—the oral cavity.

b. Pharynx—extends from the back of the nasal cavity to the top of the esophagus.

c. Esophagus—extends from the pharynx to the stomach.

d. Stomach—just below the diaphragm on the left side of the body.

e. Small intestine—extends from the stomach to the large intestine.

f. Large intestine—extends from the small intestine to the anus.

2. List and describe the location of the accessory organs of the digestive system.

a. Salivary glands—located in the oral cavity.

b. Liver—lies just below the diaphragm on the right side of the body.

c. Gallbladder—lies on posterior side of the liver.

d. Pancreas—located behind the stomach, attached to the duodenum.

3. Name the four layers of the wall of the alimentary canal.

a. Mucosa or mucous membrane

b. Submucosa

c. Muscular layer

d. Serosa or serous layer

4. Distinguish between mixing movements and propelling movements.

A mixing movement is a wavelike motion back and forth. A propelling movement is one where the muscle contraction occurs in the wall of the tube but the muscles just ahead in the tube relax.

5. Define peristalsis.

Peristalsis is defined as the rhythmic propelling movements that occur in the alimentary canal.

6. Explain the relationship between peristalsis and receptive relaxation.

Receptive relaxation is where the muscular wall ahead of peristaltic contraction relaxes. This allows the tubular contents to be pushed along the canal.

7. Describe the general effects of parasympathetic and sympathetic impulses on the alimentary canal.

Parasympathetic impulses generally increase the activity of the digestive system. Sympathetic impulses

generally are opposite of the parasympathetic impulses, thereby decreasing the activity of the digestive system.

This would then mean that peristalsis increases when innervated by the parasympathetic nervous system and would decrease when innervated by the sympathetic nervous system.

8. Discuss the functions of the mouth and its parts.

The mouth receives food and prepares it for digestion by mechanically breaking up the size of solid particles and mixing them with saliva. The cheeks are the outer layers of skin, pads of subcutaneous fat, and the muscles associated with expression and chewing. The lips are highly mobile structures that contain skeletal muscles and the sensory receptors that surround the mouth. They are used in distinguishing the temperature and texture of foods. The tongue is a body of skeletal muscle and taste receptors. The function of the tongue is to mix food particles with saliva during chewing and move food toward the pharynx during swallowing.

9. Distinguish among the lingual, palatine, and pharyngeal tonsils.

The lingual tonsils are found on the root of the tongue and are rounded masses of lymphatic tissues. The

palatine tonsils are masses of lymphatic tissues found in the back of the mouth, on either side of the tongue, and closely associated with the palate. The pharyngeal tonsils, also known as the adenoids, are masses of lymphatic tissue that occur on the posterior wall of the pharynx, above the border of the soft palate.

10. Compare the primary and secondary teeth.

Primary teeth are the first set of teeth that erupt through the gums at regular intervals between the ages of six months and two and one-half years. There are twenty primary teeth - ten in each jaw. The secondary teeth begin to appear about age six but may not be completed until somewhere between ages seventeen and twenty-five.

There are thirty-two secondary teeth—sixteen in each jaw.

11. Explain how the various types of teeth are adapted to perform specialized functions.

The incisors are chisel-shaped, and their sharp edges bite off relatively large pieces of food. The cuspids are cone-shaped, and they grasp and tear food. The bicuspids and molars have somewhat flattened surfaces and are specialized for grinding food particles.

12. Describe the structure of a tooth.

Each tooth consists of two main portions called the crown and the root. The crown is the portion above the

gum and is covered by glossy white enamel. Beneath the enamel is the bulk of the tooth, which is made up of dentin. Dentin surrounds the central cavity, which houses the blood vessels, nerves and connective tissue. The root is enclosed by cementum, which is surrounded by the periodontal ligament. The region where the crown and root meet is called the neck.

13. Explain how a tooth is anchored in its socket.

Cementum and the periodontal ligament anchor the tooth.

14. List and describe the locations of the major salivary glands.

The parotid glands are the largest salivary glands and are located in front of, and somewhat below, each ear between the skin of the cheek and the masseter muscle. The submandibular glands are located in the floor of the mouth on the inside surface of the lower jaw. The sublingual glands are the smallest of the salivary glands and are on the floor of the mouth under the tongue.

15. Explain how the secretions of the salivary glands differ.

The parotid glands secrete a clear, watery fluid that is rich in amylase. The submandibular glands secrete a

serous fluid with some mucous, making it more viscous than the parotid gland secretion. The sublingual glands secrete a thick and stringy mucous fluid.

16. Discuss the digestive functions of saliva.

The serous cells found in the salivary glands produce a watery fluid that contains amylase. Amylase is a digestive enzyme that splits starch and glycogen molecules into disaccharides. This is the first step of carbohydrate digestion.

17. Name and locate the three major regions of the pharynx.

a. Nasopharynx—located above the soft palate.

b. Oropharynx—located behind the soft palate and projects downward to the upper border of the epiglottis.

c. Laryngopharynx—located from the upper border of the epiglottis downward to the lower border of the cricoid cartilage of the larynx.

18. Describe the mechanism of swallowing.

The steps in the mechanism of swallowing are:

a. The soft palate raises, preventing food from entering the nasal cavity.

b. The hyoid bone and the larynx are elevated; the epiglottis closes off the top of the trachea so that food is less likely to enter.

c. The tongue is pressed against the soft palate, sealing off the oral cavity from the pharynx.

d. The longitudinal muscles in the pharyngeal wall contract, pulling the pharynx upward toward the food.

e. The lower portion of the inferior constrictor muscles relaxes, opening the esophagus.

f. The superior constrictor muscles contract, stimulating a peristaltic wave to begin in the pharyngeal muscles. This wave forces the food into the esophagus.

19. Explain the functions of the esophagus.

The esophagus functions as a tube that transports substances from the pharynx to the stomach.

20. Describe the structure of the stomach.

The stomach is a J-shaped, pouch-like organ. Thick folds called rugae mark its inner lining. Its mucous

membrane lining contains the gastric pits that are the openings for the gastric glands that secrete digestive enzymes.

21. List the enzymes in gastric juice, and explain the function of each enzyme.

a. Pepsin—is a protein-splitting enzyme, which is the beginning of nearly all types of dietary protein. The

chief cells secrete pepsinogen (the precursor of pepsin) that then combines with hydrochloric acid to

form pepsin.

b. Intrinsic factor—aids in the absorption of vitamin B12.

22. Explain how gastric secretions are regulated.

Parasympathetic impulses and the hormone gastrin enhance the gastric secretions. The presence of the food in the small intestine reflexly inhibits the gastric secretions.

23. Describe the mechanism that controls the emptying of the stomach.

The chyme accumulates near the pyloric sphincter. This muscle begins to relax. The pyloric region of the

stomach then pumps the chyme a little at a time into the small intestine. The rate at which the stomach empties is dependent upon the fluidity of the chyme and the type of food present.

24. Describe the enterogastric reflex.

The enterogastric reflex inhibits the gastric peristalsis and the secretion when the food enters the small intestine.

25. Explain the mechanism of vomiting.

Sensory impulses travel from the site of stimulation to the vomiting center in the medulla oblongata, and a number of motor responses follow. These include taking a deep breath, raising the soft palate and thus closing the nasal cavity, closing the opening to the trachea (glottis), relaxing the circular muscle fibers at the base of the esophagus, contracting the diaphragm so that it moves downward over the stomach, and contracting the abdominal wall muscles so that pressure inside the abdominal cavity increases. As a result, the stomach is squeezed from all sides, forcing its contents upward and out through the esophagus, pharynx, and mouth.

26. Describe the location of the pancreas and the pancreatic duct.

The pancreas is an elongated, somewhat flattened organ that is posterior to the stomach and behind the parietal peritoneum. It is attached to the duodenum by the pancreatic duct, which runs the length of the pancreas.

27. List the enzymes in pancreatic juice, and explain the function of each enzyme.

a. Pancreatic amylase—functions to digest carbohydrates.

b. Pancreatic lipase—functions to digest triglycerides.

c. Trypsin—functions to digest protein.

d. Chymotrypsin—functions to digest protein.

e. Carboxypeptidase—functions to digest protein.

f. Nucleases—functions to break nucleic acids into nucleotides.

28. Explain how pancreatic secretions are regulated.

Secretin stimulates the release of pancreatic juice that has a high bicarbonate ion concentration.

Cholecystokinin stimulates the release of pancreatic juice that has a high concentration of digestive enzymes.

Acidic chyme in the duodenum triggers the release of pancreatic juice. As the chyme moves through the

intestine the pancreatic juice is inhibited.

29. Describe the structure of the liver.

The liver is enclosed in a fibrous capsule and divided into lobes by connective tissue. Each lobe is further subdivided into hepatic lobules. These are the functional units of the liver. Each lobule consists of hepatic cells that radiate outward from a central vein.

30. List the major functions of the liver.

a. Carbohydrate metabolism

b. Lipid metabolism

c. Protein metabolism

d. Glycogen and vitamin storage

e. Blood filtering

f. Detoxification

g. Secretion of bile

31. Describe the composition of bile.

Bile is composed of bile salts, bile pigments (bilirubin and biliverdin), cholesterol, and electrolytes.

32. Trace the path of bile from a bile canaliculus to the small intestine.

The bile flows from the bile canal into hepatic ducts. The ducts then merge to form the common hepatic duct. It then can flow into the gallbladder for storage. The common hepatic and cystic duct form the common bile duct. This then empties into the duodenum.

33. Explain how gallstones form.

Gallstones form as a result of cholesterol precipitating out of solution and crystallizing. This can result if the bile becomes too concentrated, the hepatic cells secrete too much cholesterol, or the gallbladder is inflamed.

34. Define cholecystokinin.

Cholecystokinin is a hormone that is released in response to chyme in the duodenum. It then triggers the release of pancreatic juice from the pancreas, and bile from storage in the gallbladder.

35. Explain the functions of bile salts.

Bile salts emulsify fats and aid in the absorption of fatty acids, cholesterol, and certain vitamins.

36. List and describe the locations of the parts of the small intestine.

a. Duodenum—the first twenty-five centimeters of the small intestine, it lies behind the parietal peritoneum.

It is the most fixed portion of the small intestine.

b. Jejunum—the proximal two-fifths of the remainder of the small intestine.

c. Ileum—the remainder of the small intestine.

37. Name the enzymes of the intestinal mucosa, and explain the function of each enzyme.

a. Peptidases—splits peptides into amino acids.

b. Sucrase—splits sucrose into glucose.

c. Maltase—splits maltose into fructose.

d. Lactase—splits lactose into galactose.

e. Intestinal lipase—splits fats into fatty acids and glycerol.

38. Explain regulation of the secretions of the small intestine.

These secretions are stimulated by the direct contact with chyme, which provides both chemical and mechanical stimuli, and by reflexes triggered by distention of the intestinal wall. It is inhibited by the lack of chyme in the small intestine.

39. Describe the functions of the intestinal villi.

a. The villi serve to increase the surface area of the intestinal wall.

b. Monosaccharides, amino acids, fatty acids, and glycerol are absorbed by the villi.

c. Fat molecules with longer chains of carbon atoms enter the lacteals of the villi.

d. Other digestive products enter the villi and are carried away by the blood.

40. Summarize how each major type of digestive product is absorbed.

a. Monosaccharides are absorbed by the villi by diffusion, facilitated diffusion, or active transport. The

blood then carries them away.

b. Amino acids are absorbed by the villi by means of active transport. The blood then carries them away.

c. Fatty acids and glycerol are absorbed by diffusion into the lacteals of the villi. They are then carried away by lymph.

d. Diffusion and active transport into the villi absorb electrolytes.

e. Water is absorbed by osmosis into the villi.

41. Explain control the movement of the intestinal contents.

The major mixing movement is segmentation, in which small, ring-like, contractions occur periodically, cutting the chyme into segments moving it back and forth. Peristaltic waves propel the chyme through the small intestine. These are weak waves so that the chyme moves slowly through the small intestine.

42. List and describe the locations of the parts of the large intestine.

The cecum is a dilated, pouchlike structure that hangs slightly below the ileocecal opening. This represents the beginning of the large intestine. The colon is divided into four parts. The ascending colon begins at the cecum and travels upward against the posterior abdominal wall to a point just below the liver. It turns sharply to the left and becomes the transverse colon. This is the longest and most movable part of the large intestine. As the transverse colon approaches the spleen, it turns abruptly downward and becomes the descending colon. At the brim of the pelvis, the descending colon makes an S-shaped curve, called the sigmoid colon, and then becomes the rectum. The rectum is firmly attached to the sacrum and it ends about five centimeters below the tip of the coccyx. It now is known as the anal canal. The anal canal is the last two and one-half to four centimeters of the large intestine. It ends at the anus, which opens to the outside of the body.

43. Explain the general functions of the large intestine.

a. It has little or no digestive function.

b. It secretes mucous.

c. Absorption is generally limited to water and electrolytes.

d. Formation and storage of feces.

44. Describe the defecation reflex.

A person holds a deep breath and contracts the abdominal wall muscles. This increases the internal abdominal pressure and forces the feces into the rectum. As the rectal wall distends, this triggers the defecation reflex.

Peristaltic waves in the descending colon are stimulated, and the internal anal sphincter relaxes. The external sphincter relaxes and the feces are forced to the outside.

45. What are the effects of altered rates of absorption, due to aging, in the small intestine?

Because the small intestine is the site of absorption of nutrients, it is here that noticeable signs of aging on digestion arise. Subtle shifts in the microbial species that inhabit the small intestine alter the rates of absorption of particular nutrients. With age, the small intestine becomes less efficient at absorbing vitamins A, D, and K and the mineral zinc. This raises the risk of deficiency symptoms—effects on skin and vision due to a lack of vitamin A; weakened bones from inadequate vitamin D; impaired blood clotting seen in vitamin K deficiency;

and slowed healing, decreased immunity, and altered taste evidenced in zinc deficiency.

46. How does digestive function change with age?

Older people sometimes do not chew food thoroughly because thinning enamel makes teeth more sensitive to hot and cold foods, gums recede, and teeth may loosen.

Slowing peristalsis in the digestive tract may cause heartburn and constipation.

Aging affects nutrient absorption in the small intestine.

Accessory organs to digestion also age, but not necessarily in ways that affect health.

Chapter 17 out line

2007-12-06T14:38:00.000-08:00

I. Introduction

A. Digestion is the breakdown of foods into forms that cell membranes can absorb.

B. Mechanical digestion breaks large pieces of food into smaller ones without altering their chemical composition.

C. Chemical digestion breaks down food into simpler chemicals.

D. The organs of the digestive system carry out the processes of ingestion, propulsion, absorptions, defecation, and digestion.

E. The alimentary canal is composed of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal.

F. The accessory organs of the digestive system are salivary glands, liver, gallbladder, and pancreas.

II. General Characteristics of the Alimentary Canal

A. Introduction

1. The alimentary canal is a muscular tube that passes through the body’s ventral cavity.

2. The structure of its wall, how it moves food, and its innervation are similar throughout its length.

B. Structure of the Wall

1. The four layers of the alimentary wall are the mucosa, submucosa, muscular layer, and serosa.

2. The mucosa is located as the inner lining and is composed of epithelial tissue, a small amount of connective tissue, and some smooth muscle.

3. The functions of the mucosa are to protect the tissues beneath it, secrete mucus and enzymes, and to absorb nutrients.

4. The submucosa is located deep to the mucosa and is composed of loose connective tissue, glands, blood vessels, lymphatic vessels, and nerves.

5. The functions of the submucosa are to nourish surrounding tissues and to carry away absorbed substances.

6. The muscular layer is located between the submucosa and serosa and is composed of two coats of smooth muscle tissue.

7. When the circular fibers contract, the diameter of the tube decreases.

8. When the longitudinal fibers contract, the tube shortens.

9. The serosa layer is located superficial to the muscular layer and is composed of the visceral peritoneum.

10. The functions of the serosa are to moisten and lubricate the outside of the organ.

C. Movements of the Tube

1. The two types of motor functions of the alimentary canal are mixing and propelling.

2. Mixing occurs when smooth muscles in small segments of the tube contract rhythmically.

3. Peristalsis is a wavelike motion.

4. Peristalsis occurs when a ring of contraction moves down the wall of the tube.

D. Innervation of the Tube

1. Branches of the sympathetic and parasympathetic nervous system innervate the alimentary canal.

2. The innervation of the alimentary canal maintains muscular tone

and regulates strength, rate, and velocity of muscular contractions.

3. The submucosal plexus is important for controlling secretions by the gastrointestinal tract.

4. The myenteric plexus is important for gastrointestinal motility.

5. The functions of parasympathetic impulses are to increase the activities of the digestive system.

6. The functions of sympathetic impulses are to decrease the activities of the digestive system.

III. Mouth

A. Introduction

1. The functions of the mouth are to receive food and to begin digestion.

2. Mastication is chewing.

3. The mouth is surrounded by lips, cheek, tongue, and palate.

4. The oral cavity is the space between the tongue and palate.

5. The vestibule of the mouth is the space between the teeth, cheeks, and lips.

B. Cheeks and Lips

1. The cheeks form the lateral walls of the mouth and consist of skin, fat, muscles, and an inner moist lining.

2. The lips surround the mouth opening and consist of skeletal muscles, sensory receptors, and skin.

3. The reddish color of lips is due to the many blood vessels near their surfaces.

C. Tongue

1. The tongue is located in the floor of the oral cavity.

2. Mucous membranes cover the tongue.

3. The frenulum of the tongue is a membranous fold that anchors the tongue to the floor of the mouth.

4. The body of the tongue is composed of skeletal muscles.

5. Muscles of the tongue function to mix food particles and push food to the back of the throat during swallowing.

6. Papillae of the tongue are rough projections on the surface of the tongue.

7. Functions of papillae are to provide friction and to house taste buds.

8. The root of the tongue is anchored to the hyoid bone.

9. Lingual tonsils are located on the root of the tongue.

D. Palate

1. The palate forms the roof of the oral cavity and consists of a hard part and a soft part.

2. The hard palate is formed by the palatine processes of the maxillary bones and palatine bones.

3. The soft palate is formed by a mucous membrane and muscles.

4. The uvula is a downward extension of the soft palate.

5. The function of the uvula is to prevent food or liquids from entering the nasal cavity.

6. Palatine tonsils are located in the back of the mouth on either side of the palate.

7. Pharyngeal tonsils are located on the posterior wall of the pharynx, above the border of the soft palate.

E. Teeth

1. The primary teeth are the first set of teeth to develop.

2. The secondary teeth are the permanent teeth.

3. The secondary teeth consist of 32 teeth.

4. The arrangement of secondary teeth are two incisors, cuspid, two bicuspids, and three molars (from midline to back).

5. Wisdom teeth are the third set of molars.

6. Chewing increases the surface area of food particles.

7. Incisors are specialized to bite off large pieces of food.

8. Cuspids are specialized to grasp and tear food.

9. Bicuspids and molars are specialized to grind food.

10. The crown of a tooth is the portion of the tooth above the gum line.

11. The root of a tooth is the portion of the tooth below the gum line.

12. The neck of a tooth is the area where the crown and root meet.

13. Enamel consists of calcium salts.

14. Dentin is living cellular tissue beneath enamel.

15. The root canal is located in the root of a tooth and contains blood vessels and nerves.

16. The pulp cavity is located in the crown of the tooth and contains blood vessels, nerves and connective tissue called pulp.

17. Cementum is bonelike material that surrounds the root.

18. A periodontal ligament is a fibrous structure that surrounds cementum and anchors the tooth to the jaw.

IV. Salivary Glands

A. Introduction

1. Salivary glands secrete saliva.

2. The functions of saliva are to moisten food, bind food together, and begin the chemical digestion of carbohydrates.

3. The three pairs of major salivary glands are parotid glands, submandibular glands, and sublingual glands.

B. Salivary Secretions

1. Two cell types of salivary glands are serous and mucous.

2. Serous cells produce watery fluid that contains amylase.

3. Mucous cells produce mucus.

4. Amylase digests carbohydrates.

5. Salivary glands are innervated by both sympathetic and parasympathetic nerves.

6. Sympathetic fibers stimulate the glands to secrete a small volume of viscous saliva.

7. Parasympathetic fibers stimulate the glands to secrete a large volume of watery saliva.

C. Major Salivary Glands

1. The largest of the major salivary glands is the parotid.

2. The parotid glands are located anterior and inferior to each ear.

3. A parotid duct is located within the buccinator muscle and opens into the mouth just opposite the upper second molar on either side of the jaw.

4. The parotid glands secrete a water fluid rich in amylase.

5. The submandibular glands are in the floor of the mouth on the inside surfaces of the lower jaws.

6. The submandibular glands secrete primarily serous fluid.

7. Ducts of submandibular glands open inferior to the tongue.

8. The sublingual glands are located on the floor of the mouth inferior to the tongue.

9. The sublingual glands secrete primarily mucus.

10. The ducts of sublingual glands open beneath the tongue.

V. Pharynx and Esophagus

A. Introduction

1. The pharynx is a cavity posterior to the nasal and oral cavities.

2. The pharynx and esophagus function in swallowing.

B. Structure of the Pharynx

1. The pharynx connects the nasal and oral cavities with the larynx and esophagus.

2. The three divisions of the pharynx are the nasopharynx, oropharynx, and laryngopharynx.

3. The nasopharynx is located behind the nasal cavity.

4. The nasopharynx provides a passageway for air.

5. The oropharynx is located behind the oral cavity.

6. The oropharynx is a passageway for food and air.

7. The laryngopharynx is located just inferior to the oropharynx.

8. The laryngopharynx is a passageway to the esophagus.

9. Constrictor muscles function to pull the pharyngeal walls inward during swallowing.

C. Swallowing Mechanism

1. The events of the first stage of swallowing are chewing of food and the mixing of food with saliva.

2. The events of the second stage of swallowing are pushing of food toward the pharynx and the triggering of the swallowing reflex.

3. The events of the third stage of swallowing are movements of food through the esophagus and to the stomach.

4. The actions of the swallowing reflex are raising of soft palate, elevation of larynx and hyoid bone, pressing of tongue against soft palate, contraction of pharyngeal muscles, opening of the esophagus, and movement of food into the esophagus.

D. Esophagus

1. The esophagus is a passageway for food.

2. The esophagus propels food from the pharynx to the stomach.

3. The esophagus descends through the thoracic cavity.

4. The esophageal hiatus is an opening in the diaphragm.

5. Mucous glands are scattered throughout the submucosa of the esophagus.

6. The lower esophageal sphincter is located where the esophagus and stomach join and functions to prevent regurgitation of food.

VII. Stomach

A. Introduction

1. The shape of the stomach is J-shaped.

2. The location of the stomach is just inferior to the diaphragm in the upper left portion of the abdominal cavity.

3. Rugae are thick folds in the lining of the stomach.

4. The functions of the stomach are to mix food with gastric juice, begin protein digestion, to begin a small amount of absorption, and movement of food into the small intestine.

B. Parts of the Stomach

1. The four parts of the stomach are cardiac, fundic, body, and plyloric.

2. The cardiac region is the region near the esophageal opening.

3. The fundic region is a pouch that extends superior to the cardiac portion.

4. The body of the stomach is the main part of the stomach.

5. The pyloric region is the narrow region that is continuous with the small intestine.

6. The pyloric sphincter is located between the pylorus and the duodenum and functions to control the movement of food into the small intestine.

C. Gastric Secretions

1. Gastric pits are openings of gastric glands.

2. The three cell types of gastric glands are parietal, chief, and mucous.

3. Mucous cells secrete mucus.

4. Chief cells secrete digestive enzymes.

5. Parietal cells secrete hydrochloric acid and intrinsic factor.

6. Gastric juice is a mixture of the secretions of mucous, parietal, and chief cells.

7. Pepsin is an enzyme that digests proteins.

8. The function of pepsinogen is to be converted to pepsin when needed.

9. The function of hydrochloric acid in the stomach is to convert pepsinogen into pepsin and to destroy pathogens.

10. The coating of the stomach is important for protecting the stomach wall from digestive enzymes and acids.

11. The function of intrinsic factor is to aid in the absorption of vitamin B₁₂.

D. Regulation of Gastric Secretions

1. Somatostatin is produced in the stomach and functions to inhibit acid secretion.

2. Parasympathetic innervation stimulates the release of gastric juice.

3. Gastrin is produced the stomach and functions to increase the secretory activity of gastric glands.

4. The three stages of gastric secretion are cephalic, gastric, and intestinal.

5. The events of the cephalic phase are secretion of gastric juice before food enters the stomach.

6. The events of the gastric phase are distension of the stomach and the release of more gastric juice.

7. The events of the intestinal phase are the movement of food into the small intestine.

8. Cholecystokinin is produced by the small intestine and functions to inhibit gastric secretions and decreases gastric motility.

E. Gastric Absorption

1. The stomach absorbs alcohol, some drugs, salts, and a small amount of water.

2. Most nutrients are absorbed in the small intestine.

F. Mixing and Emptying Actions

1. A stomachache results from the rise of internal pressure in the stomach.

2. Chyme is food substances that have been mixed with gastric juice.

3. Peristaltic waves push chyme toward the pylorus of the stomach.

4. Stomach contractions push chyme a little at a time into the duodenum

and backwards into the stomach, mixing it further.

5. The lower esophageal sphincter prevents regurgitation of food.

6. The rate at which the stomach empties depends on the fluidity of the chyme and its contents.

7. Liquids usually pass first through the stomach.

8. The enterogastric reflex is a reflex involving the small intestine and the stomach. It is triggered by distension of the small intestine wall and inhibits peristalsis in the stomach to slow down movement of food into the duodenum.

9. Vomiting results from a complex reflex that empties the stomach in the reverse of the normal direction.

VIII. Pancreas

A. Structure of the Pancreas

1. The pancreas is located close to the duodenum posterior to the parietal peritoneum.

2. Pancreatic acinar cells produce digestive enzymes and make up the bulk of the pancreas.

3. Acini are clusters of acinar cells.

4. The pancreatic ducts extend the hepatopancreatic ampulla and empties into the duodenum.

5. Hepatopancreatic ampulla is a dilated tube that receives the pancreatic duct and hepatic duct.

6. The hepatopancreatic sphincter is the sphincter that surrounds the hepatopancreatic ampulla.

B. Pancreatic Juice

1. Pancreatic juice contains many enzymes and bicarbonate ions.

2. The function of pancreatic amylase is to digest carbohydrates.

3. The function of pancreatic lipase is digest lipids.

4. The functions of trypsin, chymotrypsin, and carboxypeptidase are to digest proteins.

5. Zymogen granules are granules that store pancreatic enzymes.

6. The function of trypsinogen is to be converted to trypsin.

7. The functions of nucleases are to digest nucleic acids.

C. Regulation of Pancreatic Secretion

1. Parasympathetic fibers cause the pancreas to release pancreatic juice.

2. The function of secretin is to stimulate the pancreas to release pancreatic juice with a high concentration of bicarbonate ions.

3. The release of cholecystokinin is triggered by the presence of chyme in the small intestine.

4. The action of cholecystokinin on the pancreas is to release pancreatic juice that has a high concentration of digestive enzymes.

IX. Liver

A. Introduction

1. The largest internal organ is the liver.

2. The liver is located in the upper right abdominal quadrant.

B. Liver Structure

1. The two large lobes of the liver are the right and left.

2. The falciform ligament is a fold that separates the lobes of the liver and anchors the liver to the posterior abdominal wall.

3. The two small lobes of the liver are caudate and quadrate.

4. The porta hepatis is where blood vessels and ducts enter or exit the liver.

5. The coronary ligament is a ligament that attaches the liver to the diaphragm.

6. Hepatic lobules are divisions of a liver lobe.

7. A hepatic lobule consists of many hepatic cells radiating outward from a central vein.

8. Hepatic sinusoids are vascular channels in hepatic lobules.

9. Kupffer cells are macrophages of the liver.

10. Bile canaliculi are canals within hepatic lobules that receive secretions from hepatic cells.

11. Hepatic ducts are formed from bile ductules of neighboring hepatic lobules.

C. Liver Functions

1. The liver carries on many important metabolic activities.

2. The liver plays a key role in carbohydrate metabolism by helping maintain the normal blood glucose concentrations.

3. The liver plays a key role in lipid metabolism by oxidizing fatty acids, synthesizing lipoproteins, phospholipids, and cholesterol.

4. The liver plays a key role in protein metabolism by deaminating amino acids, forming urea, synthesizing plasma proteins, and converting amino acids to other forms of amino acids.

5. The liver stores glycogen, iron, and vitamins A,D, and B₁₂.

6. Liver cells help destroy worn out red blood cells.

7. The liver removes toxic substances from the blood.

8. The liver’s role in digestion is to secrete bile.

D. Composition of Bile

1. Bile is secreted by hepatic cells.

2. Bile contains water, bile salts, bile pigments, cholesterol, and electrolytes.

3. Hepatic cells use cholesterol to make bile salts.

4. Bile pigments are products of the breakdown of hemoglobin.

5. Jaundice results from an accumulation of bile pigments in the blood stream.

E. Gallbladder

1. The gallbladder is located inferior to the liver.

2. The cystic duct is the duct of the gallbladder and opens into the common bile duct.

3. The common bile duct is formed from the cystic duct and common hepatic duct and opens into duodenum.

4. Gallstones form when bile is too concentrated, hepatic cells secrete to much cholesterol, or if the gallbladder is inflamed.

F. Regulation of Bile Release

1. Cholecystokinin triggers the gallbladder to release bile.

2. Cholecystokinin is released in response to presence of lipids and proteins in the small intestine.

G. Functions of Bile Salts

1. Functions of bile salts are to aid digestive enzymes by emulsifying fats, and facilitate the absorption of fat soluble vitamins.

2. Emulsification is the breaking of fat globules into smaller droplets.

3. Lack of bile salts results in poor lipid absorption and vitamin deficiencies.

X. Small Intestine

A. Introduction

1. The small intestine extends from the pyloric sphincter to the large intestine.

2. The small intestine receives secretions from the pancreas, gallbladder, and liver.

3. The functions of the small intestine are to complete digestion, absorption of nutrients, and movement of solid wastes to the large intestine.

B. Parts of the Small Intestine

1. The three parts of the small intestine are duodenum, jejunum, and ileum.

2. The duodenum is located posterior to the parietal peritoneum just beneath the stomach.

3. The jejunum is located in the abdominal cavity between the duodenum and ileum.

4. The ileum is located in the abdominal cavity between the jejunum and large intestine.

5. Mesentery is double-layered fold of peritoneum and supports the blood vessels, nerves, and lymphatic vessels that supply the intestinal wall.

6. The greater omentum is a double fold of peritoneal membrane that drapes like an apron from the stomach, over the transverses colon, and the small intestine.

7. The functions of the omentum are to prevent the spread of infections in the peritoneal cavity.

C. Structure of the Small Intestinal Wall

1. The velvety appearance of the inner wall of the small intestine is due to intestinal villi.

2. Intestinal villi are tiny projections of the mucosa of the small intestine.

3. The functions of villi are to increase the surface area of the lining of the small intestine.

4. Each villus consists of a layer of simple columnar epithelium and a core of connective tissue containing blood capillaries, a lacteal, and nerves.

5. A lacteal is a lymphatic capillary.

6. Microvilli increase the surface area intestinal cells.

7. Intestinal glands are between the bases of adjacent villi.

8. Plicae circulares are circular folds in the mucosa of the small intestine.

D. Secretions of the Small Intestine

1. Brunner’s glands are mucous-secreting glands and are located in the submucosa of the proximal portion of the duodenum.

2. Brunner’s glands secrete alkaline mucus.

3. The enzymes embedded in the membranes of epithelial cells of the small intestine are peptidase, sucrase, maltase, lactase, lipase, and enterokinase.

4. The functions of peptidases are to digest proteins.

5. The functions of sucrase, maltase, and lactase are to digest sucrose, maltose, and lactose.

6. The functions of intestinal lipase are to digest lipids.

E. Regulation of the Small Intestinal Secretions

1. Stomach contents entering the small intestine stimulate the duodenal mucous glands to release mucus.

2. Direct contact with chyme chemically and mechanically stimulates the goblet cells and intestinal glands to secrete their products.

3. Distension of the intestinal wall stimulates the parasympathetic reflexes that cause intestinal secretions.

F. Absorption in the Small Intestine

1. The most important absorbing organ is the small intestine.

2. Carbohydrate digestion begins in the mouth and is completed in the small intestine.

3. Monosaccharides are absorbed by facilitated diffusion and active transport.

4. Protein digestion begins in the stomach and is completed in the small intestine.

5. Amino acids are absorbed by active transport.

6. Fat molecules are digested almost entirely by the small intestine.

7. Chylomicrons are lipoproteins that contain lipids and proteins.

8. Chylomicrons are carried to the blood by lymph.

9. Chylomicrons in the blood transport dietary fats to muscles and adipose cells.

10. VLDL molecules, produced in the liver, transport triglycerides synthesized from excess dietary carbohydrates.

11. LDL delivers cholesterol to tissues, HDL remove cholesterol from tissues and deliver it to the liver.

12. The ions absorbed by the intestinal villi are sodium, potassium, chloride, nitrate, and bicarbonate.

13. Water is absorbed by osmosis.

G. Movements of the Small Intestine

1. Segmentation is the major mixing movement of the small intestine.

2. Chyme moves slowly through the small intestine.

3. Parasympathetics enhance mixing and peristaltic movements and sympathetics inhibits mixing and peristaltic movements.

4. A peristaltic rush is the rapid sweeping the contents into the large intestine.

5. Diarrhea results from a peristaltic rush.

6. The ileocecal sphincter joins the small intestine’s ileum and large intestine’s cecum.

XI. Large Intestine

A. Introduction

1. The large intestine is located primarily in the abdominal cavity and part of the pelvic cavity.

2. The functions of the large intestine are to form feces, eliminate solid wastes, and to absorb remaining water and electrolytes from chyme.

B. Parts of the Large Intestine

1. The parts of the large intestine are cecum, colon, rectum, and anal canal.

2. The cecum is the initial portion of the large intestine.

3. The vermiform appendix is located off the cecum and consists of lymphatic tissue.

4. The four parts of the colon are ascending colon, transverse colon, descending colon, and sigmoid colon.

5. The ascending colon is located on the right side of the abdominal cavity.

6. The transverse colon is located between the ascending and descending colon.

7. The descending colon is located on the left side of the abdominal cavity.

8. The sigmoid colon is an s-shaped portion of the colon off the descending colon.

9. The rectum is the continuation of the sigmoid colon.

10. The anal canal is the continuation of the rectum.

11. Anal columns are folds of mucous membranes in the anal canal.

12. The anus is the opening of the anal canal.

13. Two sphincters of the anus are the internal and external.

14. The internal anal sphincter is composed of smooth muscle.

15. The external anal sphincter is composed of skeletal muscle.

C. Structure of the Large Intestinal Wall

1. Teniae coli are bands of smooth muscle that extend the length of the large intestine.

2. Haustra are pouches of the large intestinal wall created by teniae coli.

3. Epiploic appendages are collections of fat in the serosa on the outer surface of the large intestine.

D. Functions of the Large Intestine

1. Mucus secretion into the large intestine is controlled by mechanical stimulation and parasympathetic impulses.

2. The functions of mucus in the large intestine are to form and store feces, eliminate feces, and absorb remaining water and electrolytes from chyme.

3. Chyme entering the large intestine contains few nutrients, nondigestible materials, water, electrolytes, mucus, and bacteria.

4. The large intestine can absorb water and electrolytes.

5. Intestinal flora is a bacterial population that exists in the large intestine.

6. The functions of intestinal flora are to synthesize some vitamins and to produce gas.

E. Movements of the Large Intestine

1. The movements of the large intestine are similar although less frequent than those of the small intestine.

2. Mass movements are produced when a large section of the intestinal wall constricts vigorously.

3. The defecation reflex is triggered by holding a deep breath and contracting the abdominal wall muscles.

4. The actions of the defecation reflex are to increase internal abdominal pressure and the forcing go feces into the rectum. Peristaltic waves are triggered and anal sphincters relax.

5. A person can inhibit defecation by contracting the external anal sphincter.

F. Feces

1. Feces are composed of materials that were not digested or absorbed, some water, electrolytes, mucus, and bacteria.
2. The pungent odor or feces results from a variety of compounds that bacteria produce.

XII. Life-Span Changes

A. Maintaining healthy teeth requires frequent dental checks, cleaning and plaque removal, plus care of the gums.

B. The effects of aging on teeth include thinning of enamel, thickening of cementum, receding of gums, and loosening of teeth.

C. Dry mouths in elderly people are usually a result of side effects of drugs.

D. Frequent heartburn may be the result of the slowing of peristalsis in the stomach.

E. Effects of aging on the small intestine include decreased efficiency in absorbing nutrients and vitamins.

F. The effects of aging on the large intestine include thinning of the lining and decreased mucus production that leads to constipation.

G. The effects of aging on the pancreas, liver, and gallbladder include a decline in their secretions.

Chapter 16 questions

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1. Explain how the lymphatic system is related to the cardiovascular system.

The lymphatic and cardiovascular systems include a network of capillaries and vessels that assist in circulating the body fluids. The lymphatic vessels transport excess fluid away from the interstitial spaces of tissues and return it to the bloodstream. The walls of both vessels are alike. For instance, they both contain a single layer of epithelial cells that allows fluids and substances to cross into them.

2. Trace the general pathway of lymph from the interstitial spaces to the bloodstream.

The lymphatic capillary system is found next to the systemic and pulmonary capillary networks. It then travels through lymph vessels into lymph nodes. It returns to lymph vessels and then is returned into the bloodstream at various points.

3. Identify and describe the locations of the major lymphatic trunks and collecting ducts.

The lymphatic trunks are named for the regions they serve. The locations can be found in fig. 16.4, on page 623.

The collecting ducts are:

Thoracic duct—It begins in the abdomen. It passes upward medially through the diaphragm to the left subclavian, where it empties.

Right lymphatic duct—It begins as the union of the right jugular, right subclavian, and right bronchomediastinal trunks. It empties into the right subclavian vein.

4. Distinguish between tissue fluid and lymph.

Lymph is tissue fluid that has entered into a lymphatic capillary.

5. Describe the primary functions of lymph.

The primary functions of lymph are to return the proteins to the bloodstream that have leaked out of the blood capillaries and to transport bacteria and other foreign particles to the lymph nodes.

6. Explain why physical exercise promotes lymphatic circulation.

The contractions of the skeletal muscles, pressure changes due to the actions of breathing muscles, and smooth muscle contractions of the larger lymphatic trunks all aid in the movement of lymph through the body.

7. Explain how a lymphatic obstruction leads to edema.

Continuous movement of fluid from the interstitial spaces into the lymphatic system stabilizes the volume of fluids in these spaces. When an obstruction occurs, the tissue fluid builds up and causes edema.

8. Describe the structure and functions of a lymph node.

Each lymph node is enclosed in a capsule of fibrous connective tissue and subdivides into compartments. The compartments contain dense masses of lymphocytes and macrophages. These masses, called nodules, are the structural units of a lymph node. Lymph nodes function in lymphocyte production and phagocytosis of foreign substances, damaged cells, and cellular debris.

9. Locate the major body regions occupied by lymph nodes.

The major body regions include: cervical region, axillary region, inguinal region, pelvic cavity, abdominal cavity, thoracic cavity, and supratrochlear region.

10. Describe the structure and functions of the thymus.

The thymus is a soft, bilobed structure whose lobes are surrounded by a capsule of connective tissue. It is composed of lymphatic tissue, which is subdivided into lobules by connective tissues. The lobules contain many lymphocytes. It functions to produce T-lymphocytes that help in the immune response. It also secretes thymosin, which is thought to stimulate the maturation of T-lymphocytes after they leave the thymus.

11. Describe the structure and functions of the spleen.

The spleen is the largest lymphatic organ. It resembles a large lymph node and is subdivided into chambers or lobules. The spaces within the chambers are filled with blood instead of lymph. There are two types of tissues within the lobules of the spleen. They include:

White pulp - distributed throughout the spleen in tiny islands, composed of splenic nodules, and containing large numbers of lymphocytes.

Red pulp - surrounds the venous sinuses and contains many red blood cells along with numerous lymphocytes and macrophages.

The spleen functions to filter the blood.

12. Distinguish between innate (nonspecific) and adaptive (specific) body defenses against infection.

Nonspecific body defenses include species resistance, mechanical barriers such as the skin and mucous membranes, and chemical barriers such as enzymes, interferon, inflammation, and phagocytosis. Specific body defenses include immune mechanisms, where certain cells recognize the presence of particular foreign substances and act against them. Lymphocytes and macrophages achieve this.

13. Explain species resistance.

Species resistance is referring to the fact that a given kind of organism or species develops diseases that are unique to it. A species may be resistant to diseases that affect other species, because its tissues somehow fail to provide the temperature or chemical environment needed by a particular pathogen.

14. Name three mechanical barriers to infection.

The skin, hair, and the mucous membranes are three mechanical barriers to infection.

15. Describe how enzymatic actions function as defense mechanisms against pathogens.

Enzymes provide a chemical barrier to pathogens. By splitting components of the pathogen or decreasing the pH, the enzyme can have lethal effects on pathogens.

16. Distinguish among the chemical barriers (interferons, defensins, collectins, and complement proteins), and give examples of their different actions.

Interferons stimulate uninfected cells to synthesize antiviral proteins that block proliferation of viruses;

stimulate phagocytosis; and enhance activity of cells that help resist infections and stifle tumor growth.

Defensins make holes in bacterial cell walls and membranes.

Collectins provide broad protection against a wide variety of microbes by grabbing onto them.

Activation of complement proteins in plasma stimulates inflammation, attracts phagocytes, and enhances phagocytosis.

17. Describe Natural Killer (NK) Cells and their action.

NK cells are a small population of lymphocytes. NK cells defend the body against various viruses and cancer by secreting cytolytic substances called perforins.

18. List the major effects of inflammation, and explain why each occurs.

Localized redness—result of blood vessel dilation and the increase in blood volume of affected tissues.

Swelling—result of increased blood volume and increased permeability of nearby capillaries.

Heat—due to the presence of blood from deeper body parts, which is generally warmer than that near the surface.

Pain—results from the stimulation of nearby pain receptors.

19. Identify the major phagocytic cells in the blood and other tissues.

The most active phagocytic cells of the blood are neutrophils and monocytes. Macrophages are fixed phagocytic cells found in lymph nodes, spleen, liver, and lungs. This constitutes reticuloendothelial tissue.

20. List possible causes of fever, and explain the benefits of fever.

Viral or bacterial infection stimulates certain lymphocytes to secrete IL-1, which temporarily raises body temperature.

Physical factors, such as heat or ultraviolet light, or chemical factors, such as acids or bases, can cause fever.

Elevated body temperature and the resulting decrease in blood iron level and increased phagocytic activity hamper infection.

21. Distinguish between an antigen and a hapten.

An antigen is a foreign substance, such as a protein, polysaccharide or a glycolipid, to which lymphocytes

respond. A hapten is a molecule that by itself cannot stimulate the immune response. It must combine with a larger molecule.

22. Review the origin of T cells and B cells.

T cells originate in the thymus. B cells are those processed in another part of the body, probably the fetal liver.

23. Explain the immune response.

The lysosomal digestive process of phagocytosis of an invading bacterium releases antigens. They are moved to the macrophage’s surface membrane. They are then displayed on the membrane with major histocompatibility complex. If the antigen then fits the helper T cell, it becomes activated. At this point, the

helper T cell seeks out the appropriate T cell and by attaching to it, activates the T cell into a response. Cell-mediated

immunity (CMI) is when a T cell, for example, attaches itself to antigen-bearing cells and interacts with the foreign cells directly.

24. Define cytokine.

Cytokines (lymphokines) are a variety of polypeptides that are synthesized and secreted by T cells and macrophages. These enhance various cellular responses to antigens. They stimulate the synthesis of

lymphokines from other T cells, help activate resting T cells, cause T cells to proliferate, stimulate the

production of leukocytes in the red bone marrow, cause growth and maturation of B cells, and activate macrophages.

25. List three types of T cells and describe the function of each in the immune response.

a. Helper T cells—mobilize the immune system to stop a bacterial infection through a series of complex steps.

b. Memory T cells—provide for no delay in the response to future exposures to an antigen.

c. Cytoxic T cells—recognize non-self antigens that cancerous or virally infected cells display on their surfaces.

26. Define clone of lymphocytes.

Clone of lymphocytes refers to cells that are derived from one early cell that are capable of responding to a certain antigen. As there are many differing antigens, there are also many differing varieties of clones.

27. Explain humoral immunity.

A B cell is activated when it binds to an activated T cell.

An activated B cell proliferates, enlarging its clone.

Some activated B cells specialize into antibody-producing plasma cells.

Antibodies react against the antigen-bearing agent that stimulated their production.

An individual’s diverse B cells defend against a very large number of pathogens.

28. Explain how a B cell is activated.

B cells become activated when they encounter an antigen whose molecular shape fits the shape of the B cell’s antigen receptors. As a result of this combination, the B-cells proliferate by mitosis and its clone is enlarged.

This mechanism for activation is similar to the lock and key model used by enzymes and substrates.

29. Explain the function of plasma cells.

Plasma cells are some of the newly formed members of the activated B cell’s clone. They make use of their DNA information and protein-synthesizing mechanism to produce antibody molecules.

30. Describe an immunoglobulin molecule.

An immunoglobulin molecule consists of two identical light changes of amino acids and two identical heavy chains of amino acids. See figure 16.20, page 637.

31. Distinguish between the variable region and the constant region of an immunoglobulin molecule.

Variable regions are the portion of one end of each of the heavy and light chains consists of variable sequences of amino acids making them specific for specific antigen molecules. Constant regions are the remaining portions of the chains whose amino acid sequences are very similar from molecule to molecule.

32. List the major types of immunoglobulins, and describe their main functions.

Immunoglobulin G (IgG)—occurs in plasma and tissue fluids.

Immunoglobulin A (IgA)—occurs in milk, tears, nasal fluid, gastric juice, intestinal juice, bile, and urine.

Immunoglobulin M (IgM)—develops in blood plasma.

Immunoglobulin D (IgD)—is important in activating B cells.

Immunoglobulin E (IgE)—occurs in exocrine secretions and is associated with allergic reactions.

33. Describe three ways in which antibody attack on a direct antigen helps in the removal of antigen.

Agglutination—antibodies combine with antigens and clumping results.

Precipitation—antibodies combine with antigens and insoluble substance forms.

Neutralization—antibodies cover the toxic portions of antigen molecules and neutralize their effects.

Lysis—antibodies cause the cell membranes to rupture.

34. Explain the function of complement.

It is a group of inactive enzymes that become activated when certain IgG or IgM antibodies combine with

antigens and the reactive sites become exposed. The activated enzymes produce chemotaxis, agglutination, opsonization, and lysis. It can also promote the inflammation reaction.

35. Distinguish between a primary and a secondary immune response.

A primary immune response occurs when B cells or T cells become activated after first encountering the antigens to which they are specifically reactant. A secondary immune response happens when memory cells are activated and increased in size, so they can respond rapidly to the antigen to which they were previously sensitized.

36. Distinguish between active and passive immunity.

Active immunity can be either naturally acquired or artificially acquired. Naturally acquired active immunity is stimulated as a result of exposure to live pathogens. Artificially acquired active immunity is stimulated by exposure to a vaccine containing weakened or dead pathogens. Passive immunity can also be either naturally acquired or artificially acquired. Naturally the antibodies passed to a fetus from a mother with active immunity stimulate acquired passive immunity. Artificially acquired passive immunity is stimulated by an injection of gamma globulin that contains antibodies.

37. Define vaccine.

A vaccine is a substance that contains an antigen that can stimulate a primary immune response against a

particular disease-causing agent, but does not cause severe disease symptoms.

38. Explain how a vaccine produces its effect.

A vaccine contains bacteria or viruses that have been killed or weakened so they cannot cause a serious

infection; or it may contain a toxin of an infectious organism that has been chemically altered to destroy its toxic effects. The antigens present still retain the characteristics needed to simulate a primary immune response.

39. Describe how a fetus may obtain antibodies from the maternal blood.

Receptor-mediated endocytosis utilizing receptor sites on cells of the fetal yolk sac transfers IgG molecules to the fetus.

40. Explain the relationship between an allergic reaction and an immune response.

Allergic reactions are closely related to immune responses in that both may involve the sensitizing of lymphocytes or the combining of antigens with antibodies. Allergic reactions are likely to be excessive and to cause tissue damage.

41. Distinguish between an antigen and an allergen.

An antigen is a substance that stimulates cells to produce antibodies. An allergen is a foreign substance capable of stimulating an allergic reaction.

42. Describe how an immediate-reaction allergic response may occur.

In an immediate-reaction allergy, the individuals have an inherited ability to synthesize abnormally large quantities of antibodies in response to certain antigens. In this instance, the allergic reaction involves the activation of B-cells.

43. List the major events leading to a delayed-reaction allergic response.

It results from repeated exposure of the skin to certain chemical substances. As a consequence of these

repeated contacts, the foreign substance and a large number of T cells collect in the skin and eventually

activate the T cells. Their actions and the actions of macrophages they attract cause the release of various chemical factors. This causes eruptions and inflammation of the skin. It is called delayed since it takes about forty-eight hours to occur.

44. Explain the relationship between a tissue rejection and an immune response.

Tissue rejection is when the immune system sees transplanted tissue as foreign and starts the immune response to try to rid the body of it.

45. Describe two methods used to reduce the severity of a tissue rejection reaction.

Matching the donor and recipient tissues may reduce it. It can also involve giving drugs that suppress the immune system.

46. How do immunosuppressant drugs increase the likelihood of success of a transplant, yet place the patient at a higher rise of developing infections?

An immunosuppressive drug interferes with the recipient’s immune response by suppressing formation of antibodies or production of T cells. This will ultimately leave the recipient relatively unprotected against infection.

47. Explain the relationship between autoimmunity and an immune response.

Autoimmunity occurs when the immune system does not distinguish between self and nonself and manufactures autoantibodies that attack the body’s own cells. For whatever reason, the autoantibodies treat a certain cell type in the body as a foreign object and signal the immune system to defend against the perceived invader.

48. Describe the causes for a decline in the strength of the immune response in the elderly.

The immune system begins to decline early in life, in part due to the decreasing size of the thymus.

Numbers of T cells and B cells do not change significantly, but activity levels do.

Proportions of the different antibody classes shift.

Chapter 16 out line

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I. Introduction

A. The lymphatic system is a vast collection of cells that travel in lymphatic vessels and the organs and glands that produce them.

B. The lymphatic system includes a network of vessels that assist in circulating body fluids.

C. Lymphatic vessels transport excess fluid away from interstitial spaces and return it to the bloodstream.

D. The organs of the lymphatic system also defend the body against infection by disease-causing agents.

II. Lymphatic Pathways

A. Lymphatic Capillaries

1. Lymphatic capillaries are microscopic, closed-ended tubes that extend into interstitial spaces.

2. The walls of lymphatic capillaries are similar to blood capillaries.

3. The thin walls of capillaries make it possible for tissue fluid from interstitial space to enter the lymphatic capillaries.

4. Lymph is fluid inside a lymphatic capillary.

5. Lacteals are lymphatic capillaries in the lining of the small intestine and function to transport fats to the venous system.

B. Lymphatic Vessels

1. The walls of lymphatic vessels are similar to those of veins.

2. Lymphatic vessels have valves that prevent backflow of lymph.

3. Larger lymphatic vessels lead to lymph nodes.

4. After leaving nodes, lymphatic vessels merge in larger lymphatic trunks.

C. Lymphatic Trunks and Collecting Ducts

1. Lymphatic trunks drain lymph from lymphatic vessels and are named for the regions they serve.

2. Examples of lymphatic trunks are lumbar, intestinal, intercostal, bronchomediastinal, subclavian, and jugular trunks.

3. Lymphatic trunks join one of two collecting ducts.

4. The two collecting ducts are the thoracic duct and right lymphatic duct.

5. The thoracic duct is located along side the aorta in the abdominal and thoracic cavity and empties into the left subclavian vein.

6. The thoracic duct drains lymph from the intestinal, lumbar, and intercostal trunks, as well as from the left subclavian, left jugular, and left bronchomediastinal trunks.

7. The right lymphatic duct is located on the right side of the thorax and empties into the right subclavian vein.

8. The right lymphatic duct drains right jugular, right subclavian, and right bronchomediastinal trunks.

9. After leaving the two collecting ducts, lymph enters the venous system and becomes part of the plasma.

III. Tissue Fluid and Lymph

A. Introduction

1. Lymph is tissue fluid that has entered a lymphatic capillary.

2. Lymph formation depends on tissue fluid formation.

B. Tissue Fluid Formation

1. Capillary blood pressure filters water and small molecules from plasma and the resulting fluid consists of water, nutrients, gases, and hormones (a similar composition to plasma).

2. Water is drawn back into capillaries because of plasma colloid osmotic pressure.

C. Lymph Formation

1. Filtration from the plasma normally exceeds reabsorption, leading to the formation of tissue fluid.

2. Tissue fluid moves into lymphatic capillaries because of interstitial fluid hydrostatic pressure.

3. Lymph formation prevents edema.

D. Lymph Function

1. Lymphatic vessels in the small intestine play a major role in the absorption of dietary fats.

2. Lymph returns small proteins that most of the blood capillaries filtered to the bloodstream.

3. Lymph transports foreign particles to lymph nodes.

4. Lymphatic capillaries can receive proteins and foreign particles that blood capillaries cannot because the epithelial cells that form the walls of lymphatic vessels overlap each other but are not attached.

5. The lumen of a lymphatic capillary remains open because their epithelial cells are attached to surrounding connective tissue cells by protein filaments.

IV. Lymph Movement

A. Introduction

1. The hydrostatic pressure of tissue fluid drives lymph into lymphatic capillaries.

2. Muscular activity largely influences movement of lymph through lymphatic vessels.

B. Lymph Flow

1. Lymph is under relatively low hydrostatic pressure.

2. Contracting skeletal muscles compress lymphatic vessels.

3. Lymph does not flow back because of valves.

4. Breathing aids lymph circulation by creating a relatively low pressure in the thorax and a relatively high pressure in the abdomen during inhalation.

C. Obstruction of Lymph Movement

1. Conditions that interfere with lymph movement causes fluid to accumulate within interstitial spaces.

2. The continuous movement of lymph from interstitial spaces into blood capillaries and lymphatic capillaries stabilizes the volume of fluid in interstitial spaces.

V. Lymph Nodes

A. Introduction

1. Lymph nodes are located along lymphatic pathways.

2. Lymph nodes contain lymphocytes and macrophages which fight invading microorganisms.

B. Structure of a Lymph Node

1. The hilum of a lymph node is the indented region.

2. Afferent lymphatic vessels are those that carry lymph to a node.

3. Efferent lymphatic vessels are those that carry lymph away from a node.

4. Lymph nodules are divisions of a lymph node.

5. Germinal centers contain dense masses of actively dividing lymphocytes and macrophages.

6. Tonsils are composed of partially encapsulated lymph nodules.

7. Peyer’s patches are located in the mucosal lining of the distal portion of the small intestine and are composed of M cells, macrophages, and lymphocytes.

8. Lymph sinuses are a network of chambers and channels through which lymph circulates.

C. Locations of Lymph Nodes

1. Lymph nodes generally occur in groups or chains along the paths of larger lymphatic vessels but are absent in the central nervous systems.

2. Major locations of lymph nodes are cervical region, axillary region, supratrochlear region, inguinal region, pelvic cavity, abdominal cavity, and thoracic cavity.

3. Lymph nodes of the cervical region are associated with lymphatic vessels that drain the skin of the scalp and fact, as well as tissues of the nasal cavity and pharynx.

4. Lymph nodes of the axillary region are associated with lymphatic vessels that drain the upper limbs, wall of the thorax, mammary glands, and upper abdominal wall.

5. Lymph nodes of the supratrochlear region are associated with lymphatic vessels that drain the elbow region.

6. Lymph nodes of the inguinal region are associated with lymphatic vessels that receive lymph from the lower limbs, external genitalia, and lower abdominal wall.

7. Lymph nodes of the pelvic cavity are associated with lymphatic vessels that drain the pelvic viscera.

8. Lymph nodes of the abdominal cavity are associated with lymphatic vessels that drain the abdominal viscera.

9. Lymph nodes of the thoracic cavity are associated with lymphatic vessels that drain thoracic viscera and the internal wall of the thorax.

D. Functions of Lymph Nodes

1. The two primary functions of lymph nodes are to filter potentially harmful particles from lymph and to monitor body fluids.

2. Along with the red bone marrow, lymph nodes are centers for lymphocyte production.

3. Lymphocytes attack viruses, bacteria, and other parasitic cells.

4. The functions of macrophages are to engulf and destroy foreign substances, damaged cells, and cellular debris.

VI. Thymus and Spleen

A. Thymus

1. The thymus is composed of lymphocytes and connective tissues and is located in the mediastinum.

2. After puberty, the thymus begins to shrink.

3. Most cells of the thymus gland are thymocytes.

4. The hormones secreted by the thymus gland are called thymosins.

5. Thymosins function to stimulate maturation of T lymphocytes.

B. Spleen

1. The largest lymphatic organ is the spleen.

2. The spleen is located in the upper left portion of the abdominal cavity.

3. The spleen resembles a large lymph node.

4. White pulp contains many lymphocytes.

5. Red pulp contains red blood cells, lymphocytes, and macrophages.

6. The functions of the spleen are to remove foreign particles, damaged red blood cells, and cellular debris from the blood.

VII. Body Defenses Against Infection

A. An infection is the presence of pathogens.

B. Examples of pathogens are bacteria, protozoa, fungi and viruses.

C. Innate defenses are general defenses and protect against many types of pathogens and include species resistance, mechanical barriers, chemical barriers, enzyme actions, interferon, complement, natural killer cells, inflammation, phagocytosis, and fever.

D. Adaptive defenses are very precise defense mechanisms targeting specific pathogens and are carried out by lymphocytes.

VIII. Innate Defenses

A. Species Resistance

1. Species resistance refers to the fact that a given kind of organism or species develops diseases that are unique to it.

2. A species may be resistant to diseases that affect other species because its tissues somehow fail to provide the temperature of chemical environment that a particular pathogen requires.

B. Mechanical Barriers

1. Mechanical barriers prevent the entrance of some infectious agents.

2. Examples of mechanical barriers are skin, mucous membranes, and hair.

3. The first line of defense is a mechanical barrier.

4. The second line of defense is a collection of the other nonspecific defenses.

C. Chemical Barriers

1. Chemical barriers are body fluids containing enzymes or antimicrobial substances.

2. Examples of chemical barriers are gastric juice, interferons, defensins, and collectins.

3. Interferon is produced by lymphocytes and fibroblasts and its functions include stimulation of phagocytosis, and to prevent viral infections.

4. Defensins are produced by white blood cells, and certain epithelial cells.

5. The functions of defensins are to make holes in bacterial cells walls and to destroy certain pathogens.

6. Collectins are proteins and their functions include protecting the body against viruses, bacteria, and yeasts.

D. Complement

1. Complement is a group of proteins in plasma and other body fluids that interact in a series of reactions.

2. Activation of complement stimulates inflammation, attracts phagocytes, and enhances phagocytosis.

E. Natural Killer Cells

1. Natural killer cells are a small population of lymphocytes.

2. Functions of natural killer cells are to protect the body against cancer and viruses.

3. Perforins are cytolytic substances secreted by natural killer cells.

F. Inflammation

1. Inflammation produces redness, swelling, heat and pain.

2. Redness of inflammation is the result of dilated blood vessels.

3. Swelling of inflammation is the result of increases capillary permeability.

4. Heat of inflammation is the result of the entry of blood from deeper body parts.

5. Pain of inflammation is the result of stimulation of pain receptors.

6. Cells that commonly migrate to areas of inflammation are neutrophils and monocytes.

7. Pus is the result of an accumulation of white blood cells, bacterial cells, and cellular debris.

8. The functions of inflammation are to prevent the spread of infection, to clear infection, and to promote healing of damaged tissues.

G. Phagocytosis

1. Phagocytosis removes foreign particles.

2. Examples of phagocytic cells are neutrophils, monocytes, and macrophages.

3. The mononuclear phagocytic system is monocytes, macrophages, and neutrophils that are spread throughout the body.

H. Fever

1. A fever begins when a viral or bacterial infection stimulates lymphocytes to produce interleukin-1.

2. The functions of fever are to increase phagocytosis and to prevent bacteria and other pathogens from obtaining iron

IX. Adaptive (Specific) Defenses or Immunity

A. Introduction

1. Immunity is resistance to particular pathogens or to their toxins or metabolic by-products.

2. An immune response is based on the ability to distinguish molecules that are part of the body from those that are foreign.

3. Antigens are molecules that can elicit an immune response.

4. Lymphocytes and macrophages carry out immune responses.

B. Antigens

1. Receptors on lymphocyte surfaces enable cells to recognize foreign antigens.

2. Antigens may be proteins, polysaccharides, glycoproteins, or glycolipids.

3. The antigens most effective in eliciting an immune response is large and complex, with few repeating parts.

4. A hapten is a small molecule that must bind to a larger molecule to elicit an immune response.

5. Examples of haptens are chemicals found in drugs, household cleaners, dust, and skins of certain animals.

C. Lymphocyte Origins

1. T cells are derived from red bone marrow and the thymus gland.

2. B cells are derived from red bone marrow.

3. The blood distributes B cells.

4. B cells and T cells are abundant in lymph nodes, the spleen, bone marrow, and the intestinal lining.

D. Lymphocyte Functions

1. The cellular immune response is cell-to-cell contact between a T cell and antigen cell.

2. Cytokines are produces by T cells.

3. Examples of cytokines are interleukins, colony-stimulating factors, interferons, and tumor necrosis factors.

4. Functions of cytokines are to stimulate the production of lymphocytes, block viral replication, stimulate phagocytosis, stimulate production of antibodies, and to stop growth of tumor cells.

5. T cells may also secrete toxins that kill antigen-bearing cells, growth-inhibiting factors that prevent target cell growth, or interferon that prevent viral and tumor cell proliferation.

6. B cells differentiate into plasma cells.

7. Plasma cells produce antibodies.

8. The humoral immune response is the immune response that is mediated by antibodies.

9. A clone is a cell that is identical to the cell from which it was derived.

10. Different varieties of T cells and B cells have a particular type of antigen receptor on their cell membranes that can respond only to a specific antigen.

E. T Cells and the Cellular Immune Response

1. A lymphocyte must be activated before it can respond to an antigen.

2. T cell activation requires the presence of processed fragments of antigen attached to the surface of another kind of cell.

3. Antigen-presenting cells are macrophages, B cells, and other cell types.

4. T cell activation begins when a macrophage phagocytizes a bacterium and moves the antigens of the bacterium to its membrane.

5. The major histocompatibility complex is a complex of proteins found on the surface of antigen-presenting cells.

6. MHC antigens help T cells recognize an antigen as foreign.

7. Class I MHC antigens are located on cell membranes of all cells except red blood cells.

8. Class II MHC antigens are located on cell membranes of antigen-presenting cells, thymus cells, and activated T cells.

9. The functions of helper T cells are to stimulate B cells to produce antigens and to secrete cytokines.

10. The functions of cytotoxic T cells are to eliminate viral infected cells and tumor cells.

11. The functions of memory T cells are to respond to an antigen during a future exposure and to differentiate immediately into cytotoxic T cells.

F. B Cells and the Humoral Immune Response

1. Introduction

a. B cells may become activated when an antigen binds to its membrane-bound receptor.

b. Upon activation, B cells divide repeatedly.

c. T cells help B cells by releasing cytokines that stimulate B cell proliferation and antibody production.

d. The functions of memory B cells are to respond rapidly to subsequent exposures to a specific antigen.

e. The functions of plasma cells are to secrete antibodies.

f. An immune response may include several types of antibodies manufactured against a single microbe because pathogens often have different antigens on their surfaces.

g. A polyclonal response is the production of several different antibodies against one pathogen.

2. Antibody Molecules

a. Antibodies are soluble, globular proteins.

b. Each antibody is composed of four chains of amino acids that are linked together.

c. The light chains are identical and contain about half the number of amino acids as the heavy chains.

d. The heavy chains are identical and contain twice as many amino acids as the light chains.

e. The five major types of antibodies are distinguished by a particular kind of heavy chain.

f. The variable region is the part of the antibody that contains variable sequences of amino acids.

g. Variable regions are specialized to react to the shape of a specific antigen molecule.

h. Antigen-binding sites are specialized ends of antibodies that bind to antigens.

i. Idiotypes are the particular parts of antigen-binding sites that actually bind to antigens.

j. Constant regions are the parts of an antibody other than their variable regions.

3. Types of Immunoglobulins

a. The five major types of immunoglobulins are IgG, IgA, IgM, IgD, and IgE.

b. The three types of immunoglobulins that make up the bulk of circulating antibodies are IgG, IgA, and IgM.

c. IgG is found in tissue fluid and plasma.

d. The functions of IgG are to defend against bacterial, viruses, and toxins; it also activates complement.

e. IgA is found in exocrine gland secretions.

f. The functions of IgA are to defend against bacteria and viruses.

g. IgM is found in plasma.

h. The functions of IgM are to react with antigens occurring on red blood cells and to activate complement.

i. IgD is found in the cell membranes of B cells.

j. The functions of IgD are to act as receptors for B cells.

k. IgE is located in exocrine gland secretions.

l. The functions of IgE are to promote inflammation and allergic reactions.

4. Antibody Actions

a. The three ways antibodies react to antigens are to directly attack antigens, activates complement, or stimulate localized changes (inflammation) that help prevent the spread of the pathogen.

b. In a direct attack, antibodies combine with antigens and cause them to clump.

c. Phagocytic cells can engulf antigen-bearing pathogens more readily when they have clumped together.

d. Antibodies can also cover the toxic portions of antigens and neutralize their effects.

e. Complement is activated by the binding of certain antibodies to antigens.

f. Functions of complement are opsonization, chemotaxis, cell lysis, and inflammation.

g. IgE antibodies are usually attached to membranes of mast cells.

h. Mast cells release their biochemicals when antigens combine to antibodies on their surfaces.

G. Immune Responses

1. The primary immune response occurs when a person is first exposed to an antigen.

2. Following a primary immune response, some B cells produce memory cells.

3. The secondary immune response occurs when a person is later exposed to an antigen and memory cells are activated.

H. Practical Classification of Immunity

1. Naturally acquired active immunity develops when a person is naturally exposed to an antigen.

2. Artificially acquired active immunity develops when a person is given a vaccine.

3. A vaccine is a preparation that includes a antigen that stimulate a primary immune response.

4. Artificially acquired passive immunity occurs when a person is injected with antibodies or anti-toxins.

5. Naturally acquired passive immunity occurs when antibodies are passed across the placenta or through mother’s milk.

I. Allergic Reactions

1. An allergic reaction is an immune response against a nonharmful substance.

2. Allergens are substances that trigger allergic reactions.

3. An immediate-reaction allergy occurs when an allergens bind to IgE antibodies and allergy mediators are released from mast cells and basophils.

4. Anaphylactic shock is a severe form of immediate-reaction allergy that may lead to death.

5. Antibody-dependent cytotoxic reactions occur when an antigen binds a specific cell, simulating phagocytosis and complement-mediated lysis of the antigen.

6. Immune complex reactions occur when antigen-antibody complexes cannot be cleared from the body.

7. Autoimmunity refers to the loss of the ability to tolerate self-antigens.

8. A delayed-reaction allergy occurs when a person is repeatedly exposed to an allergen and the allergic reaction occurs about 48 hours after exposure to the antigen.

J. Transplantation and Tissue Rejection

1. Transplanted tissues and organs include corneas, kidneys, lungs, pancreases, bone marrow, skin, livers, and hearts.

2. A tissue rejection reaction is the destruction of transplanted tissue by the recipient’s immune system.

3. Tissues are rejected because the cell surface molecules (MHC antigens) of the donor tissue are recognized as foreign by the recipient.

4. Isografts are grafts from an identical twin.

5. Autografts are grafts from one’s self.

6. Allografts are grafts from another person.

7. Xenografts are grafts from a different species.

8. Immunosuppressive drugs are used to reduce rejection of transplanted tissues.

K. Autoimmunity

1. Autoantibodies are antibodies that cannot distinguish self from nonself.

2. Reasons people develop autoimmunities are viruses may incorporate some self proteins into its coating and the body then recognizes the self proteins as foreign in all cells, T cells may never learn to differentiate between self and nonself cells, or some antigens may resemble self antigens.

3. Scleroderma is a condition caused by autoimmunity that produces fatigue, swollen joints, stiff fingers, hardened blood vessels, and a mask like face.

X. Life-Span Changes

A. The immune system begins to decline early in life.

B. By age 70, the thymus is one-tenth of its original size.

C. Elderly people have a higher risk of developing cancer and infections because the strength of their immune systems has declined.

D. AIDS is more difficult to diagnose in older people because physicians do not initially suspect the condition.

E. Elderly people may not be candidates for certain medical treatments because of their declining immune systems.

Chapter 15 questions

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Cardiovascular System

1. Describe the general structure, function, and location of the heart.

The heart is a hollow, cone-shaped, muscular pump located in the thorax. The average adult heart is about nine centimeters long and seven centimeters wide. It functions to pump deoxygenated blood to the lungs and pump oxygenated blood to the body.

2. Describe the pericardium.

The pericardium consists of an outer fibrous bag know as the fibrous pericardium that surrounds a more delicate, double-layered sac. The inner layer of the sac, the visceral pericardium covers the heart. At the base of the heart, the visceral layer turns back upon itself to become the parietal pericardium, which forms the inner lining of the fibrous pericardium.

3. Compare the layers of the cardiac wall.

The epicardium (visceral pericardium) functions as a protective layer. This layer consists of connective tissue covered by epithelium. Its deeper portion often contains adipose tissue.

The myocardium is relatively thick and consists largely of cardiac muscle tissue. The muscle fibers are arranged in planes, separated by connective tissues, which are richly supplied with blood capillaries, lymph capillaries, and nerve fibers.

The endocardium consists of epithelium and connective tissue containing many elastic and collagenous fibers.

The connective tissues house the Purkinje fibers, which function with the conduction system of the heart. This layer is continuous with the inner linings of the blood vessels attached to the heart.

4. Identify and describe the locations of the chambers and valves of the heart.

The upper chambers are called atria. These have relatively thin walls and receive blood returning to the heart.

The lower chambers are called ventricles. They receive blood from the atria and force blood out of the heart into the arteries.

There are two atrioventricular valves (A-V valves). The tricuspid valve is located between the right atrium and the right ventricle. The bicuspid (mitral) valve is located between the left atrium and the left ventricle.

There are two semilunar valves. The pulmonary semilunar valve is found between the right ventricle and the pulmonary artery. The aortic semilunar valve is found between the left ventricle and the aorta. All four valves function to prevent backflow between the respective chambers and vessels.

5. Describe the skeleton of the heart, and explain its function.

Rings of dense fibrous connective tissue surround the proximal ends of the pulmonary trunk and the aorta. This provides attachments from heart valves and muscle fibers. These fibrous rings, together with other masses of dense fibrous tissue in the upper portion of the interventricular septum, constitute the skeleton of the heart.

6. Trace the path of blood through the heart.

The deoxygenated blood enters the right atrium from the superior and inferior vena cava and the coronary sinus. It passes through the tricuspid valve to the right ventricle. It passes through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk further divides into the right and left pulmonary arteries. These arteries carry the deoxygenated blood to the lungs. After the gas exchange is complete, the oxygenated blood is returned to the left atrium from the right and left pulmonary veins (two on each side for a total of four). It flows through the bicuspid (mitral) valve to the left ventricle. It then is pumped through the aortic semilunar valve into the aortic arch and beyond.

7. Trace the path of blood through the coronary circulation.

The blood is supplied to the tissues of the heart by the first two branches of the aorta called the right and left coronary arteries. The openings to these vessels lie just beyond the aortic semilunar valve. It then goes through the capillary system of the heart. Branches of the cardiac veins that roughly parallel the coronary arteries drain the blood that has passed through the capillaries. These veins empty into the coronary sinus that is located on the posterior side of the heart emptying into the right atrium.

8. Describe a cardiac cycle.

A cardiac cycle is one complete heartbeat. This consists of atrial systole, which is the atria contracting while ventricular diastole (ventricular relaxation) occurs. The second part of the cycle is when atrial diastole (atria relaxing) occurs while ventricular systole (ventricles contracting) occurs. This entire process is one complete cardiac cycle.

9. Describe the pressure changes that occur in the atria and ventricles during a cardiac cycle.

When the atria are relaxed, the pressure begins to rise as they fill with blood. As the atria contract, the pressure rises suddenly, forcing the remaining blood into the ventricles. Pressure is low in the ventricles when they are filling but begins to rise as they fill with blood. It rises sharply as the ventricles contract forcing the blood out into the appropriate vessels.

10. Explain the origin of heart sounds.

The first heart sound (lubb) occurs during ventricular contraction, when the tricuspid and bicuspid valves are closing. The second heart sound (dupp) occurs during ventricular relaxation, when the pulmonary and aortic semilunar valves are closing.

11. Describe the arrangement of the cardiac muscle fibers.

Cardiac muscle fibers are arranged in branching networks to pass impulses through the heart so it contracts as a unit.

12. Distinguish between the roles of the S-A node and the A-V node.

The S-A (sinoatrial) node is a small mass of specialized muscle tissue just beneath the epicardium. The fibers are self-exciting so they initiate impulses that spread to the myocardium and stimulate the muscle fibers to contract. The S-A node initiates one impulse seventy to eighty times per minute. Because it generates the rhythmic contractions of the heart, it is often called the pacemaker.

The A-V (atrioventricular) node is located in the inferior portion of the septum and just beneath the endocardium, providing the only normal conduction pathway between the atrial and ventricular syncytia.

13. Explain how the cardiac conduction system controls the cardiac cycle.

Once the impulse leaves the S-A node (sinoatrial node), it passes into the atrial syncytium and the atria

contract almost simultaneously. From there, the impulse travels along a system continuous with the atrial

muscle fibers and into the A-V node (atrioventricular node) which is the only normal route to the ventricular syncytia. Because of the small diameter of nerve fibers from here, the impulse is slowed enough for the atria to empty and the ventricles to fill with blood. From here, the impulse passes through the A-V node and into the A-V bundle (atrioventricular bundle or bundle of His), which is comprised of larger diameter nerves. The impulse speeds up and splits into two branches (right and left) on the way to the Purkinje fibers. These fibers are even larger, and cause the impulse to move even faster. The Purkinje fibers branch into the papillary muscles and downward to the apex of the heart. There, they curve upward and branch along the entire walls of the ventricles until they become continuous with the cardiac muscle fibers. The whorl design of the myocardium causes the ventricles to contract in a “wringing” fashion that squeezes the blood out and into the arteries.

14. Describe and explain a normal ECG pattern.

A normal ECG pattern consists of a P wave, a QRS complex, and a T wave. The P wave is caused by a

depolarization of the atrial fibers just before they contract. The QRS complex is caused by the depolarization of ventricular fibers just prior to contraction of the ventricular walls. The T wave is caused by the relatively slow repolarization of the ventricular muscle fibers. The QRS complex obscures atrial repolarization.

15. Discuss how the nervous system regulates the cardiac cycle.

When the body needs the heart to slow down, the medulla oblongata sends impulses down the

parasympathetic tracts to the S-A and A-V nodes. The release of acetylcholine causes the heart to decrease in activity. The parasympathetic nerves seem to be the main control of the heart. So, if the impulses increase, the heart will slow down. If the impulses decrease, the heart will speed up.

The sympathetic nervous system also has tracts that innervate the S-A and A-V nodes, along with other areas within the atria and ventricles. These nerves secrete norepinephrine, which causes the heart to speed up and increase the force of its contractions. The cardiac center of the medulla controls the impulses from the parasympathetic and sympathetic nerves by interpreting information from the pressoreceptors (baroreceptors) in the aortic sinus and aortic arch, and the carotid sinuses in the carotid arteries.

16. Describe two factors other than the nervous system that affect the cardiac cycle.

Temperature change and certain ions influence the cardiac cycle. If the body temperature rises, the heart rate will increase, as with a fever. If the body temperature decreases, the heart rate will slow accordingly. K+ and Ca++ are the most important ions that influence the cardiac cycle. Potassium affects the electrical potential of the cell membrane, thereby altering its ability to reach the threshold for impulse conduction. Calcium affects the cardiac muscle’s ability to contract as the sarcoplasmic reticulum stores less and relies on extracellular calcium for contraction to occur.

17. Distinguish between an artery and an arteriole.

Arteries are strong, elastic vessels that are adapted for carrying the blood away from the heart under high pressure. An arteriole is a smaller, finer branch of an artery.

18. Explain control of vasoconstriction and vasodilation.

Vasoconstriction occurs when the smooth muscle in the wall of the vessels is stimulated by the vasomotor fibers of the sympathetic branches of the autonomic nervous system. This causes contraction to occur, thereby decreasing the diameter of the vessel. If the vasomotor impulses are inhibited, the muscle relaxes and the diameter of the vessel increases. This is known as vasodilation.

19. Describe the structure and function of a capillary.

Capillaries are the smallest blood vessels and connect the smallest arterioles to the smallest venules. They

consist of a single layer of squamous epithelial cells that are continuous with the endothelium of the larger vessels. A capillary provides the semipermeable membranes through which substances in the blood are exchanged for substances in the tissue fluid surrounding body cells.

20. Describe the function of the blood-brain barrier.

The function of the blood-brain barrier is to shield delicate brain tissue from toxins in the bloodstream and from biochemical fluctuations that could overwhelm the brain.

21. Explain control of blood flow through a capillary.

This is regulated mainly by the smooth muscles that encircle the capillary entrances. These muscles form

precapillary sphincters, which may close a capillary by contracting or opening it by relaxing. The control of the precapillary sphincters is not clear.

22. Explain how diffusion functions in the exchanges of substances between blood plasma and tissue fluid.

Blood entering the capillaries of the tissues has higher concentrations of molecules and ions than in the tissue fluid itself. Diffusion is the process of moving from areas of higher concentrations to lower concentrations.

The nutrients and oxygen tend to move into the tissues because the concentrations of these substances are higher in the blood. The wastes, such as carbon dioxide, are in higher concentrations in the tissues so these

diffuse into the blood plasma.

23. Explain why water and dissolved substances leave the arteriolar end of a capillary and enter the venular end.

The blood pressure at the arteriolar end is greater than in the capillary itself. This allows for filtration of substances to occur at this site. The blood pressure decreases as the blood moves through a capillary, making the outward filtration force less than the osmotic pressure at the venular end. Consequently, there is a net movement of water and dissolved materials, into the venular end of the capillary by osmosis.

24. Describe the effect of histamine on a capillary.

Histamine will increase capillary permeability.

25. Distinguish between a venule and a vein.

A venule is a microscopic vessel that continues from the capillaries and merges with other venules to form veins. Veins are the counterpart to the arterial system that carries blood back to the heart.

26. Explain how veins function as blood reservoirs.

The valves prevent a backflow of blood. Their smooth muscle layer is much less developed, allowing more blood to remain in the vein. In times of hemorrhage accompanied by the drop in arterial blood pressure, the

muscular walls are stimulated reflexly by sympathetic nerve impulses. The resulting venous constriction pushes out the extra blood, which raises the blood pressure.

27. Distinguish between systolic and diastolic blood pressures.

The maximum pressure achieved during ventricular contraction is called the systolic pressure. The diastolic pressure is the lowest pressure that remains in the arteries during ventricular diastole.

28. Name several factors that influence the blood pressure, and explain how each produces its effect.

a. The amount of blood that enters the arterial system with each ventricular contraction. This is known as heart action.

b. The amount of blood cells and plasma volume in the cardiovascular system, which is known as blood volume.

c. The amount of peripheral resistance within the walls of the blood vessels.

d. The viscosity (the ease with which molecules in a fluid slide past one another).

29. Describe the control of blood pressure.

Two important mechanisms for blood pressure control involve the regulation of cardiac output and the peripheral resistance. Starling’s law of the heart ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers. Pressoreceptors trigger the neural regulation of the heart rate.

Chemicals, such as epinephrine, emotions, physical exercise, and increased body temperature can also play a role in regulation of heart rate, thereby influencing the cardiac output. Peripheral resistance is regulated primarily by the changes in the diameters of arterioles. The vasomotor center of the medulla oblongata has neural control of the smooth muscle in the arteriole wall. Chemical substances, including carbon dioxide,

oxygen, and hydrogen ions, also influence peripheral resistance by affecting the smooth muscle in the walls of arterioles and the actions of precapillary sphincters.

30. List the major factors that promote the flow of venous blood.

a. Skeletal muscle contractions

b. Respiratory movements

c. Venoconstriction

31. Define central venous pressure.

The pressure that is within the right atrium of the heart is known as the central venous pressure.

32. Distinguish between the pulmonary and systemic circuits of the cardiovascular system.

The pulmonary circuit of the cardiovascular system consists of those vessels that carry the blood from the heart to the lungs and back to the heart. The systemic circuits of the cardiovascular system are responsible for carrying the blood from the heart to all other parts of the body and back again.

33. Trace the path of the blood through the pulmonary circuit.

The deoxygenated blood leaves the right ventricle into the pulmonary trunk, which divides into the right and left pulmonary arteries. These branches penetrate the right and the left lungs, respectively. These further divide into arterioles that continue into the capillary networks associated with the walls of the alveoli, where the gas exchanges occur between the blood and the air. From these pulmonary capillaries, the blood enters the venules that eventually merge to form veins. Four pulmonary veins, two from each lung, carry the oxygenated blood back to the left atrium.

34. Explain why the alveoli normally do not fill with fluid.

The epithelial cells of the alveolar membrane are tightly joined so that most ions fail to enter the alveoli. This helps to maintain a relatively high osmotic pressure in the interstitial fluid. Osmosis will then move any water that gets into the alveoli back into the interstitial space. This mechanism prevents excess water from entering the alveoli and helps keep the alveoli from filling with fluid.

35. Describe the aorta, and name its principal branches.

The aorta is the largest artery in the body extending upward from the left ventricle. It arches over the heart to the left and descends just in front of the vertebral column.

Principal branches of the ascending aorta include the aortic sinus, which gives rise to the right and left coronary arteries. The aortic arch gives rise to the brachiocephalic artery, the left common carotid artery, and the left subclavian artery. The thoracic aorta gives rise to the brachial artery, the pericardial artery, the esophageal artery, the mediastinal artery, and the posterior intercostal artery. The abdominal aorta gives rise to the celiac artery, the phrenic artery, the superior mesenteric artery, the suprarenal artery, the renal artery, the gonadal artery, the inferior mesenteric artery, the lumbar artery, the middle sacral artery, and the common iliac arteries.

36. Describe the relationship between the major venous pathways and the major arterial pathways.

Major veins typically parallel the courses taken by major named arteries. This, with some exceptions allows the vein to be named from the major artery next to it.

37. List and describe the changes occurring in the cariovascular system as a result of aging.

Some degreee of cholesterol deposition in blood vessels may be a normal part of aging, but accumulation is great enough to lead to overt disease.

Fibrous connective tissue and adipose tissue enlarge the heart by filling in when the number and size of

cardiac muscle cells fall.

Blood pressure increases with age, while resting heart rate decreases with age.

Moderate exercise correlates to lowered risk of heart disease in older people.

Chapter 15 out line

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I. Introduction

A. The heart pumps 7,000 liters of blood through the body each day.

B. The cardiovascular system includes the heart and blood vessels.

C. The pulmonary circuit sends oxygen-depleted blood to the lungs to pick up oxygen and unload carbon dioxide.

D. The systemic circuit sends oxygen-rich blood and nutrients to the body cells and removes wastes.

II. Structure of the Heart

A. Size and Location of the Heart

1. An average size of an adult heart is generally 14 cm long and 9 cm wide.

2. The heart is bounded laterally by the lungs, anteriorly by the sternum, and posteriorly by the vertebral column.

3. The base of the heart lies beneath the second rib.

4. The apex of the heart is at the level of fifth intercostal space.

B. Coverings of the Heart

1. The pericardium is a covering that enclosed the heart and the proximal ends of the large blood vessels to which it attaches.

2. The fibrous pericardium is the outer fibrous layer of the pericardium.

3. The visceral pericardium is a serous membrane that is attached to the surface of the heart.

4. The parietal pericardium is a serous membrane that lines the fibrous layer of the pericardium.

5. The pericardial cavity is the space between the visceral pericardium and parietal pericardium.

6. Serous fluid reduces friction between the pericardial membranes as the heart moves.

C. Wall of the Heart

1. The three layers of the heart wall are endocardium, myocardium, and pericardium.

2. The epicardium is composed of a serous membrane that consists of connective tissue covered by epithelium, and it includes blood capillaries, lymph capillaries, and nerve fibers.

3. The middle layer is the myocardium.

4. The myocardium is composed of cardiac muscle tissue.

5. The inner layer is the endocardium.

6. The endocardium consists of epithelium and connective tissue that contains manly elastic and collagenous fibers. It also contains blood vessels and Purkinje fibers.

7. The endocardium of the heart is continuous with the inner lining of the blood vessels attached to the heart.

D. Heart Chambers and Valves

1. The two upper chambers of the heart are the right atrium and the left atrium.

2. Auricles are small, earlike projections of the atria.

3. The two lower chambers of the heart are the right ventricle and the left ventricle.

4. The interatrial septum separates the right and left atrium.

5. The interventricular septum separates the right and left ventricles.

6. An atrioventricular orifice is an opening between an atrium and a ventricle.

7. An atrioventricular orifice is protected by an A-V valve.

8. The atrioventricular sulcus is located between the atria and ventricles.

9. The right atrium receives blood from the superior and inferior vena cavae and the coronary sinus.

10. The tricuspid valve is located between the right atrium and right ventricle and functions to prevent the back flow of blood into the right atrium.

11. Chordae tendinae are fibrous strings and function to prevent cusps of A-V valves from swinging back into atria.

12. Papillary muscles are located in ventricular walls and contract when the ventricles contract.

13. The right ventricle receives blood from the right atrium.

14. The right ventricle pumps blood into the pulmonary trunk.

15. The pulmonary trunk divides into pulmonary arteries.

16. Pulmonary arteries deliver blood to the lungs.

17. The pulmonary valve is located between the right ventricle and pulmonary trunk and opens when the right ventricle contracts.

18. Pulmonary veins carry blood from the lungs to the left atrium.

19. Blood passes from the left atrium into the left ventricle.

20. The mitral valve is located between the left atrium and left ventricle and functions to prevent the back flow of blood into the left atrium.

21. The left ventricle pumps blood into the aorta.

22. The aortic valve is located between the left ventricle and aorta and opens when the left ventricle contracts.

23. The tricuspid and mitral valves are also called A-V valves because they are positioned between atria and ventricles.

24. The pulmonary and aortic valves are also called semilunar valves

because of their structures.

E. Skeleton of the Heart

1. The skeleton of the heart is composed of rings of dense connective tissue and other masses of connective tissue in the interventricular septum.

2. The skeleton of the heart provides attachments for the heart valves and for muscle fibers.

F. Path of Blood Through the Heart

1. Blood that is low in oxygen and rich in carbon dioxide enter the right atrium of the heart through venae cavae and the coronary sinus.

2. As the right atrium contracts, blood passes into the right ventricle.

3. When the right ventricle contracts, blood moves into the pulmonary trunk.

4. From the pulmonary arteries blood enters the lungs.

5. The blood loses carbon dioxide in the lungs and picks up oxygen.

6. Freshly oxygenated blood returns to the heart through pulmonary veins.

7. The pulmonary veins deliver blood to the left atrium.

8. When the left atrium contracts, blood passes into the left ventricle.

9. When the left ventricle contracts, blood passes into the aorta.

G. Blood Supply to the Heart

1. The first two branches of the aorta are the left and right coronary arteries.

2. Coronary arteries supply blood to the tissues of the heart.

3. The circumflex artery is located in the atrioventricular groove between the left atrium and left ventricle and supplies blood to the walls of the left atrium and left ventricle.

4. The anterior interventricular artery is located in the anterior interventricular groove and supplies blood to walls of both ventricles.

5. The posterior interventricular artery is located the posterior interventricular groove and supplies the posterior walls of both ventricles.

6. The marginal artery is located along the lower border of the heart and supplies blood to the wall of the right atrium and right ventricle.

7. Blood flow in coronary arteries is poorest during ventricular contraction because the contracting myocardium interferes with blood flow and the openings of the coronary arteries are partially blocked by cusps of the aortic valve.

8. Cardiac veins drain blood that passes through the capillaries of the myocardium.

9. The coronary sinus is an enlarged vein on the posterior surface of the heart.

III. Heart Actions

A. Introduction

1. Atrial systole is atrial contraction.

2. Ventricular diastole is ventricular relaxation.

3. Atrial diastole is atrial relaxation.

4. Ventricular systole is ventricular contraction.

5. When the atria of the heart contract, the ventricles relax.

6. When the ventricles of the heart contract, the atria relax.

B. Cardiac Cycle

1. During a cardiac cycle, the pressure within the heart chambers rises and falls which is what causes the valves to open and close.

2. The pressure in the ventricles is low during ventricular diastole.

3. During diastole, the A-V valves are open.

4. About 70% of the blood flows passively from the atria into ventricles and the remaining blood is pushed into the ventricles when the atria contract.

5. As ventricles contract, the A-V valves close.

6. When the pressure in the atria is lower than venous pressure, blood flows from the veins into atria.

7. During ventricular systole, ventricular pressure increases and the pulmonary valves open.

8. As blood flows out of the ventricles, ventricular pressure decreases.

9. The semilunar valves close when the pressure in the ventricles is lower than pressure in the aorta and pulmonary trunk.

C. Heart Sounds

1. Heart sounds are produced by the movement of blood through the heart and by the opening and closing of heart valve.

2. The first heart sound is lubb and occurs during ventricular systole

when the A-V valves close.

3. The second heart sound is dupp and occurs during ventricular diastole when the pulmonary and aortic valves close.

4. A murmur is an abnormal heart sound.

D. Cardiac Muscle Fibers

1. A functional syncytium is a mass of merging cells that act as a unit.

2. Two syncytiums of the heart are in the atrial walls and the ventricular walls.

3. The atrial syncytium and ventricular syncytium are connected by fibers of the cardiac conduction system.

E. Cardiac Conduction System

1. The cardiac conduction system is responsible for coordinating events of the cardiac cycle.

2. The S-A node is located in the wall of the right atrium and initiates one impulse after another.

3. The S-A node is called the pacemaker because it generates the heart’s rhythmic contractions.

4. As a cardiac impulse travels from the S-A node into the atrial syncytium, it goes from cell to cell via gap junctions.

5. Conducting fibers deliver impulses from the S-A node to the A-V node.

6. The A-V node is located in the inferior part of the interatrial septum and provides the only normal conduction pathway between the atrial and ventricular syncytiums.

7. Impulses are delayed as they move through the A-V node because this allows time for atria to contract.

8. From the A-V node, impulses pass to the A-V bundle.

9. The A-V bundle is located in the superior part of the interventricular septum and gives rise to bundle branches.

10. Purkinje fibers carry impulses to distant regions of the ventricular myocardium.

11. The ventricular myocardium contracts as a functioning unit.

12. Purkinje fibers are located in the inferior portion of the interventricular septum, papillary muscles, and in the ventricular walls.

13. The ventricular walls contract with a twisting motion because the muscle fibers in the ventricular walls form irregular whorls. The twisting motion produces a pushing motion.

14. Contraction of the ventricles begins at the apex of the heart and pushes blood superiorly toward the aortic and pulmonary semilunar valve.

F. Electrocardiogram

1. An electrocardiogram is a recording of the electrical changes that occur in the myocardium during a cardiac cycle.

2. An ECG is recorded by placing electrodes on the skin and connecting the electrodes to an instrument that respond to very weak electrical changes by moving a pen on a moving strip of paper.

3. A P-wave is produced when atrial fibers depolarize.

4. A QRS-wave is produced when ventricular fibers depolarize.

5. A T-wave is produced when the ventricular fibers repolarize.

6. Physician’s use ECG patterns to assess the heart’s ability to conduct impulses.

G. Regulation of Cardiac Cycle

1. The volume of blood pumped changes to accommodate cellular requirements.

2. The parasympathetic nerve to the heart is the vagus nerve

3. The vagus nerve innervates the S-A and A-V nodes.

4. The vagus nerve can alter heart rate by secreting acetylcholine onto the nodes.

5. Sympathetic fibers reach the heart via the accelerator nerves.

6. The endings of accelerator nerves secrete norepinephrine which increases the rate and force of myocardial contractions.

7. The cardiac control center controls the balance between the inhibitory actions of the parasympathetic nervous system and the stimulatory actions of the sympathetic nervous system.

8. Baroreceptors detect pressure changes.

9. When baroreceptors in the aorta detect an increase in pressure, they signal the cardioinhibitory center of the medulla oblongata.

10. If blood pressure is too high, the medulla oblongata sends parasympathetic impulses to the heart to decrease heart rate.

11. If venous blood pressure increases abnormally, sympathetic impulses flow to the heart and heart rate and contraction increases.

12. Rising body temperature increases heart action.

13. The most important ions that influence heart action are potassium and calcium.

IV. Blood Vessels

A. Introduction

1. Blood vessels form a closed circuit of tubes that carries blood from the heart to the body cells and back again.

2. Five types of blood vessels are arteries, arterioles, capillaries, venules, and vein.

3. Arteries conduct blood away from the heart and to arterioles.

4. Venules and veins conduct blood from capillaries and to the heart.

5. The capillaries are sites of exchange of substances between the blood and the body cells.

B. Arteries and Arterioles

1. Arteries are strong, elastic vessels that are adapted for carrying the blood away from the heart under high pressure.

2. Arteries give rise to arterioles.

3. The three layers of the wall of an artery are the endothelium, tunica media, and tunica adventitia.

4. The inner layer of an artery is called endothelium and functions to provide a smooth surface for blood flow and prevents blood clotting.

5. The middle layer of an artery is called the tunica media and is composed of smooth muscle fibers.

6. The outer layer is the tunica adventitia and consists of connective tissues with collagenous and elastic fibers.

7. The vasa vasorum of an artery is a series of blood vessels that supply the wall of large arteries.

8. The sympathetic nervous system innervates smooth muscle in arteries and arterioles.

9. Vasomotor fibers stimulate smooth muscle cells to contract, decreasing the diameter of the vessel.

10. Vasoconstriction is the contraction of smooth muscle cells in blood vessel walls.

11. Vasodilation is the relaxation of smooth muscle cells in the walls of blood vessels and occurs when the blood vessel diameter increases.

12.Changes in the diameters of arteries and arterioles greatly influence blood flow and blood pressure.

13. The wall of a very small arteriole consists of an endothelium and some smooth muscle cells and connective tissue.

14. Metarterioles are branches of arterioles and help regulate blood flow to an area.

15. Arteriovenous shunts are connections between arterioles and venous pathways.

C. Capillaries

1. Introduction

a. The smallest diameter blood vessels are capillaries.

b. Capillaries connect arterioles to venules.

c. The wall of a capillary consists of endothelium.

2. Capillary Permeability

a. The most permeable capillaries are located in the liver, spleen, and red bone marrow.

b. Protective and tight capillaries are located brain.

3. Capillary Arrangement

a. The higher a tissue’s rate of metabolism, the denser its capillary networks.

b. Tissues richly supplied with capillaries are muscle and nervous tissues.

c. Tissues that lack capillaries are cartilage and epithelial tissues.

d. During exercise, blood is directed to capillary networks of skeletal muscle and it bypasses some of the capillary networks of the digestive tract.

4. Regulation of Capillary Blood Flow

a. Precapillary sphincters are located at the opening of capillaries and their function is control the flow of blood into a capillary.

b. When cells have low concentrations of oxygen, precapillary sphincters relax and blood flow increases.

5. Exchanges in the Capillaries

a. The vital function of exchanging gases, nutrients, and metabolic by-products between the blood and the tissue fluid surrounding body cells occurs in the capillaries.

b. Biochemicals move through capillary walls by diffusion, filtration, and osmosis.

c. Diffusion is the most important means of transfer.

d. Oxygen and nutrients diffuse out of the capillary walls into surrounding cells because they are in a lower concentration in surrounding cells.

e. Carbon dioxide and other wastes diffuse into the capillary blood because they are in a lower concentration in the capillary blood.

f. Plasma proteins generally remain in the blood because they are too big to cross through capillary walls.

g. In filtration, hydrostatic pressure forces molecules through a membrane.

h. In the capillaries, the force for filtration is provided by blood pressure.

i. Blood pressure is greater at the arteriole end of the capillary.

j. Colloid osmotic pressure is osmotic pressure and is created by plasma proteins in the blood of capillaries.

k. At the arteriolar end of the capillary, filtration predominates.

l. At the venular end of the capillary, osmotic pressure predominates.

D. Venules and Veins

1. Venules are blood vessels that continue from capillaries and merge to form veins.

2. The middle layer of the wall of a vein is very thin and poorly developed compared to that of an artery.

3. The function of valves in veins is keep blood flowing toward the heart.

4. Veins also function as blood reservoirs.

V. Blood Pressure

A. Introduction

1. Blood pressure is the force the blood exerts against the inner walls of the blood vessels.

2. Blood pressure most commonly refers to pressure in arteries.

B. Arterial Blood Pressure

1. Systolic pressure is the maximum pressure and is created when the ventricles contract.

2. Diastolic pressure is the minimum pressure and is created when the ventricles relax.

3. A pulse is the alternate expanding and recoiling of an arterial wall.

4. Common places to detect a pulse are the radial artery, the brachial artery, the carotid artery, the temporal artery, the facial artery, the femoral artery, the popliteal artery, and the posterior tibial artery.

C. Factors that Influence Arterial Blood Pressure

1. Heart Action

a. Stroke volume is the volume of blood discharged from the ventricle with one contraction.

b. Cardiac output is the volume of blood discharged from a ventricle in one minute.

c. If stroke volume or heart rate increases, cardiac output increases.

2. Blood Volume

a. Blood volume equals the sum of the formed elements and plasma volumes in the vascular system.

b. Blood pressure is normally directly proportional to blood volume.

3. Peripheral Resistance

a. Peripheral resistance is the friction between blood and the walls of the blood vessels.

b. If peripheral resistance increases, blood flow decreases and blood pressure increases.

c. Dilation of blood vessels reduces peripheral resistance.

4. Viscosity

a. Viscosity is the thickness of a fluid.

b. As blood viscosity rises, blood pressure increases.

c. Blood cells and plasma proteins contribute to blood viscosity.

D. Control of Blood Pressure

1. Blood pressure is determined by cardiac output and peripheral resistance.

2. Cardiac output depends on the stroke volume and heart rate.

3. Stroke volume is the difference between EDV and ESV.

4. End Diastolic Volume is the volume of blood in each ventricle at the end of ventricular diastole.

5. End Systolic Volume is the volume of blood in each ventricle at the end of the ventricular systole.

6. Factors affecting stoke volume and heart rate are mechanical, neural, and chemical.

7. Preload is the mechanical stretching of a ventricular wall prior to ventricular contraction.

8. The greater the EDV, the greater the preload lengthening of myocardial fibers.

9. Starling’s Law of the Heart is the relationship between fiber length and force of contraction.

10. The more blood that enters the heart, the greater the ventricular distention, the stronger the ventricular contractions, the greater the stroke volume and the greater the cardiac output

11. The less blood that returns from veins to the heart, the less ventricular distension, the weaker the ventricular contractions, the lesser the stroke volume and the lesser the cardiac output.

12. Starling’s Law of the Heart ensures that the volume of blood discharged from the heart is equal to the volume entering its chambers.

13. If blood pressure rises, baroreceptors initiate the cardioinhibitory reflex which decreases blood pressure.

14. If blood pressure falls, the cardioaccelerator reflex occurs which increases sympathetic stimulation to the heart, which increases heart rate and cardiac output, which increases blood pressure.

15. Other factors that increase heart rate and blood pressure are emotional responses, exercise, and a rise in body temperature.

16. When arterial blood pressure suddenly increases, baroreceptors signal the vasomotor center, and sympathetic outflow to arterial walls decreases, which results in a decrease in blood pressure.

17. Chemicals that influence peripheral resistance are carbon dioxide, oxygen, and hydrogen ions.

E. Venous Blood Flow

1. Blood pressure decreases as the blood moves through the arterial system into capillary networks.

2. Blood flow through the venous system largely depends on skeletal muscle contractions and valves in veins.

3. The squeezing action of skeletal muscles helps push blood toward the heart.

4. During inspiration, the pressure in the thoracic cavity is reduced and the pressure in the abdominal cavity increases.

5. An increases in abdominal pressure will squeeze blood out of abdominal veins.

6. When venous pressure is low, sympathetic reflexes stimulate smooth muscles in the walls of the veins to contract.

F. Central Venous Pressure

1. Central venous pressure is the pressure within the heart.

2. Central venous pressure is of special interest because it affects the pressure within the peripheral veins.

3. Other factors that increase central venous pressure are an increase in blood volume or widespread venoconstriction.

4. An increase in central venous pressure can lead to peripheral edema.

VII. Paths of Circulation

A. Introduction

1. The two major pathways of blood vessels are the pulmonary circuit and the systemic circuit.

2. The pulmonary circuit consists of vessels that carry blood from the heart to the lungs and back to the heart.

3. The systemic circuit carries blood from the heart to all parts of the body and back again.

B. Pulmonary Circuit

1. Blood enters the pulmonary circuit as it leaves the right ventricle through the pulmonary trunk.

2. The pulmonary trunk divides into pulmonary arteries.

3. Within the lungs the pulmonary arteries divide into lobar branches.

4. The lobar branches give rise to arterioles that continue into capillary networks.

5. The blood in the arteries and arterioles of the pulmonary circuit is low in oxygen and high in carbon dioxide.

6. Gases are exchanged between the blood and the air as the blood moves through alveolar capillaries.

7. The arterial pressure in the pulmonary circuit is less than in the systemic circuit because the right ventricle contracts with a force less than that of the left ventricle.

8. Higher osmotic pressure of the blood removes any fluid that gets into the alveoli.

9. Blood entering the venules of the pulmonary circuit is oxygen rich and low in carbon dioxide.

10. Venules merge to form veins.

11. Pulmonary veins return blood to the left atrium and this completes the pulmonary circuit.

C. Systemic Circuit

1. Freshly oxygenated blood moves from the left atrium to the left ventricle.

2. Contraction of the left ventricle forces blood into the systemic circuit.

3. The systemic circuit includes the aorta and its branches that lead to all of the body tissues, as well as the companion system of veins that returns blood to the right atrium.

VIII. Arterial System

A. Introduction

1. The aorta is the largest diameter artery in the body.

2. The aorta extends upward from the left ventricle, arches over the heart to the left, and descends just anterior and to the left of the vertebral column.

B. Principal Branches of the Aorta

1. The ascending aorta is the first portion of the aorta.

2. An aortic sinus is a swelling of the aortic wall.

3. Coronary arteries arise from the aortic sinus.

4. Aortic bodies are small structures located within the aortic sinuses

and contain chemoreceptors that sense blood concentrations of oxygen and carbon dioxide.

5. Three arteries originating from the aortic arch are the brachiocephalic artery, the left common carotid artery, and the left subclavian artery.

6. The brachiocephalic artery supplies blood to the tissues of the upper limb and head.

7. The brachiocephalic divides into the right common carotid artery and the right subclavian.

8. The common carotids supply blood to the head and neck.

9. The subclavian arteries supply blood to the arms.

10. The descending aorta moves through the thoracic and abdominal cavity.

11. The thoracic aorta is portion of the descending aorta above the diaphragm.

12. Branches of the thoracic aorta are the bronchial, pericardial, and esophageal arteries.

13. The abdominal aorta is the portion of the descending aorta below the diaphragm.

14. Branches of the abdominal aorta are celiac, phrenic, superior mesenteric, suprarenal, renal, gonadal, inferior mesenteric, lumbar, and middle sacral arteries.

15. The celiac artery gives rise to gastric, splenic, and hepatic arteries which supply upper portions of the digestive tract, spleen and liver.

16. Phrenic arteries supply the diaphragm.

17. The superior mesenteric artery branches to many parts of the intestinal tract.

18. The suprarenal arteries supply the adrenal glands.

19. The renal arteries supply the kidneys.

20. The gonadal arteries supply the ovaries and testes.

21. The inferior mesenteric artery branches into arteries leading to the descending colon, sigmoid colon, and the rectum.

22. Lumbar arteries supply muscle of the skin and posterior abdominal wall.

23. The middle sacral artery supplies the sacrum and coccyx.

24. The abdominal aorta terminates near the brim of the pelvis and divides into common iliac arteries.

25. The common iliac arteries supply lower regions of the abdominal wall, the pelvic organs, and the lower extremities.

C. Arteries of the Neck, Head, and Brain

1. Branches of the subclavian and common carotids supply structures within the neck, head, and brain.

2. The main divisions of the subclavian artery to the neck, head, and brain are the vertebral, thyrocervical, and costocervical arteries.

3. The common carotid artery communicates with these regions by means of the internal and external carotid arteries.

4. The vertebral arteries arise from the subclavian arteries and supply the base of the neck.

5. A basilar artery is formed by the union of vertebral arteries.

6. The basilar artery divides into posterior cerebral arteries

that supply portions of the occipital and temporal lobes of the cerebrum.

7. The cerebral arterial circle is formed by the posterior cerebral arteries.

8. Functions of the cerebral arterial circle are supply brain tissue and to provide alternate routes through for blood to reach brain to circumvent for blockages and equalize blood pressure in the brain’s blood supply.

9. Thyrocervical arteries give rise to branches to the thyroid gland, parathyroid glands, larynx, trachea, esophagus, and pharynx.

10. Costocervical arteries carry blood to muscles of the neck, back and thoracic wall.

11. The common carotid arteries ascend deeply within the neck and divide to form internal and external carotid arteries.

12. The external carotid artery gives off branches to structures of the neck, face, jaw, scalp, and base of skull.

13. Main branches off external carotid arteries are superior thyroid, lingual, facial, occipital and posterior auricular arteries.

14. The superior thyroid artery supplies the hyoid bone, larynx, and thyroid gland.

15. The lingual artery supplies the tongue and salivary glands.

16. The facial artery supplies the pharynx, palate, chin, lips, and nose.

17. The occipital artery supplies the back of the scalp, the meninges, the mastoid process, and muscles of the neck.

18. The posterior auricular artery supplies the ear and scalp over the ear.

19. The external carotid artery terminates by dividing into maxillary and superficial temporal arteries.

20. The maxillary artery supplies the teeth, gums, jaws, cheek, nasal cavity, eyelids, and meninges.

21. The temporal artery supplies the parotid glands and various regions of the face and scalp.

22. The major branches of the internal carotid artery are ophthalmic, posterior communicating, and anterior choroid arteries.

23. The ophthalmic artery supplies the eyeball and various muscles and accessory organs within the orbit.

24. The posterior communicating artery forms part of the cerebral arterial circle.

25. The anterior choroids artery supplies the choroid plexus and structures within the brain.

26. The internal carotid artery terminates by dividing into anterior and middle cerebral arteries.

27. The middle cerebral artery supplies the lateral surfaces of the cerebrum.

28. The anterior cerebral artery supplies the medial surfaces of the cerebrum.

29. A carotid sinus is an enlargement of each carotid artery and contains baroreceptors that control blood pressure.

D. Arteries to the Shoulder and Upper Limb

1. As it passes into the arm, the subclavian artery becomes the axillary artery.

2. The axillary artery supplies structures of the axilla and chest wall.

3. The axillary artery becomes the brachial artery.

4. The brachial artery gives rise to deep brachial artery.

5. The branches of the brachial artery supply structures of the arm.

6. Within the elbow, the brachial artery divides into ulnar and radial arteries.

7. The branches of the ulnar artery supply structures on the ulnar side of the forearm.

8. The branches of the radial artery supply structures on the radial side of the forearm.

9. Blood supply to the wrist, hands, and fingers come from branches of the radial and ulnar arteries.

E. Arteries to the Thoracic and Abdominal Walls

1. The internal thoracic artery is a branch of a subclavian artery.

2. The internal thoracic artery gives off two anterior intercostal arteries to each of the upper six intercostal spaces.

3. The anterior intercostals arteries supply intercostal muscles and mammary glands.

4. The posterior intercostals arteries arise from the aorta and enter the intercostal spaces between the third through the eleventh ribs.

5. The posterior intercostals arteries supply intercostal muscles, the vertebrae, the spinal cord, and deep muscles of the back.

6. Branches of the internal thoracic and external iliac arteries provide blood to the anterior abdominal wall.

7. Phrenic and lumbar arteries supply the posterior and lateral abdominal wall.

F. Arteries to the Pelvis and Lower Limb

1. The abdominal aorta divides to form common iliac arteries.

2. The common iliac arteries provide blood to pelvic organs, gluteal and lower limbs.

3. Each common iliac divides into internal and external iliacs.

4. The internal iliac artery gives off branches to pelvic organs and muscles, genitals, and gluteal muscles.

5. Branches of the internal iliac artery are iliolumbar, gluteal, internal pudendal, vesical, middle rectal, and uterine arteries.

6. The iliolumbar arteries supply the ilium and muscles of the back.

7. Superior and inferior gluteal arteries supply gluteal muscles, pelvic muscles, and skin of the buttocks.

8. Internal pudendal arteries supply muscles to the distal portion of the alimentary canal, external genitals, and the hip joint.

9. Superior and inferior vesical arteries supply the urinary bladder, seminal vesicles, and prostate gland.

10. Middle rectal arteries supply the rectum.

11. Uterine arteries supply the uterus and vagina.

12. The external iliac artery provides the main blood supply to the lower limbs.

13. Two branches of the external iliac artery are inferior epigastric and deep circumflex arteries.

14. The inferior epigastric artery and deep circumflex artery supply muscles and skin of the lower abdominal wall.

15. The external iliac artery becomes the femoral artery.

16. The femoral artery gives off branches to muscles and superficial tissues of the thigh.

17. Important subdivisions of the femoral artery are superficial circumflex iliac artery, superficial epigastric artery, pudendal arteries, deep femoral, and deep genicular arteries.

18. Superficial circumflex iliac arteries supply skin and lymph nodes of the groin.

19. Superficial epigastric arteries supply skin of lower abdominal wall.

20. Superficial and deep external pudendal arteries supply skin of lower abdomen and external genitalia.

21. Deep femoral arteries supply the hip joint and thigh muscles.

22. Deep genicular arteries supply thigh muscles and knee joint.

23. The popliteal artery is derived from the femoral artery.

24. Branches of the popliteal artery supply the knee joint and muscles of the thigh and calf.

25. The popliteal artery divides into anterior and posterior tibial arteries.

26. The anterior tibial artery supplies skin and muscles of the leg.

27. The dorsalis pedis artery is derived from the anterior tibial artery.

28. The posterior tibial artery supplies skin and muscles of the leg.

29. The posterior tibial artery divides into medial and lateral plantar arteries which supply the foot.

30. The fibular artery is the largest branch of the posterior tibial artery and supplies the ankle.

IX. Venous System

A. Characteristics of Venous Pathways

1. The vessels of the venous system begin with the merging capillaries into venules, venules into small veins, and small veins into larger ones.

2. Venous pathways are hard to follow because veins commonly connect in irregular networks.

3. The larger veins typically parallel arteries.

4. The veins from most body parts converge into superior and inferior vena cavae.

B. Veins from the Brain, Head, and Neck

1. The external jugular veins drain blood from the face, scalp, and superficial regions of the neck.

2. The external jugular veins empty into subclavian veins.

3. The internal jugular veins arise from numerous veins and venous sinuses of the brain and from deep veins in various parts of the face and neck.

4. The brachiocephalic veins are formed from internal jugular and subclavian veins.

5. The brachiocephalic veins merge to give rise to the superior vena cava.

C. Veins from the Upper Limb and Shoulder

1. A set of deep veins and a set of superficial veins drain the upper limb.

2. The deep veins generally parallel the arteries in each region.

3. The superficial veins connect in complex networks beneath the skin

and also communicate with deep vessels of the upper limb.

4. The main vessels of the superficial network are the basilic and cephalic veins.

5. The basilic vein is located along the back of the forearm on the ulnar side and along the anterior surface of the elbow and joins the brachial vein.

6. The axillary vein is formed by basilic and brachial veins.

7. The cephalic veins are located on the lateral side of the upper limb and empties into the axillary vein.

8. Beyond the axilla, the axillary vein becomes the subclavian vein.

9. The median cubital vein is located on the lateral side of the forearm and in the bend of the elbow and is often a site for the retrieval of a blood sample.

D. Veins from the Abdominal and Thoracic Walls

1. Tributaries of the brachiocephalic and azygos veins drain the abdominal and thoracic walls.

2. The azygos vein originates in the dorsal abdominal wall and ascends

through the mediastinum on the right side of the vertebral columns.

3. The azygos vein drains muscle tissue of the thoracic and abdominal walls.

4. Tributaries of the azygos vein include posterior intercostal veins, hemiazygos veins, and ascending lumbar veins.

5. The superior and inferior hemiazygos veins drain posterior intercostal veins.

6. The ascending lumbar veins drain lumbar and sacral regions.

E. Veins from the Abdominal Viscera

1. Veins carry blood directly to atria of the heart, except those of the hepatic portal system.

2. The hepatic portal vein drains the stomach, intestine, pancreas, and spleen and carries blood to the liver.

3. The hepatic portal system is the venous pathway that includes the hepatic portal vein and the hepatic sinusoids.

4. Tributaries of the hepatic portal system include gastric veins, superior mesenteric, and splenic veins.

5. The gastric veins drain the stomach.

6. Superior mesenteric veins drain the intestines.

7. Splenic veins drain the spleen, pancreas, and a portion of the stomach.

8. The blood flowing to the liver in the hepatic portal system is oxygen poor and nutrient rich.

9. The liver metabolizes the nutrients.

10. Kupffer cells are located in hepatic sinusoids and function to phagocytize microbes.

11. Blood leaves the liver through hepatic veins.

12. Hepatic veins empty blood into the inferior vena cava.

13. Veins that empty into the inferior vena cava are lumbar, gonadal, renal, suprarenal, and phrenic veins.

F. Veins from the Lower Limb and Pelvis

1. Veins that drain the lower limb can be divided into deep and superficial groups.

2. The deep veins of the leg have names that correspond to arteries that they accompany.

3. The popliteal vein is formed from tibial veins.

4. The femoral vein originates from the popliteal vein.

5. The external iliac vein originates from the femoral vein.

6. The small saphenous vein begins in the lateral portion of the foot and passes upward behind the lateral malleolus.

7. The small saphenous vein ascends along the back of the calf and joins the popliteal vein.

8. The great saphenous vein originates on the medial side of the foot

and ascends upward along the medial side of the leg and thigh, and eventually joins the femoral vein.

9. The longest vein of the body is the great saphenous vein.

10. The saphenous veins communicate with deep veins of the leg and thigh.

11. In the pelvic region, vessels leading to internal iliac veins carry blood away from organs of reproduction, urinary, and digestive systems.

12. Tributaries that form the internal iliac vein are gluteal, pudendal, vesical, rectal, uterine, and vaginal veins.

13. The common iliac veins are formed from external iliac and internal iliac veins.

14. The common iliac veins merge to form inferior vena cava.

X. Life-Span Changes

1. Sixty percent of men over the age of sixty have at least one narrowed coronary artery.

2. Some degree of cholesterol deposition in blood vessels may be part of normal aging.

3. During exercise, cardiac output decreases with age.

4. Cardiovascular disease may cause enlargement of the heart.

5. The number of cardiac muscle fibers in the heart fall and fibrous and adipose tissue increases.

6. With age, heart valves begin to thicken.

7. Systolic blood pressure increases with age.

8. The increase in systolic blood pressure is due to the decreasing diameters and elasticity of arteries.

9. Resting heart rate decreases with age.

10. With age, changes in arteries include thickening of the tunica interna and a decrease of elasticity.

11. The number of capillaries declines with age.

12. Exercise can help maintain a “young” vascular system.

Chapter 14 questions

2007-12-06T14:35:00.001-08:00

1. List the major components of blood.

The blood consists of red blood cells, white blood cells, platelets, and plasma (the liquid portion).

2. Define hematocrit, and explain how it is determined.

Hematocrit (HCT) is the percentage of the cells in a blood sample. This is obtained by allowing the sample to stand (clotting is prevented), allowing the cells to separate and sink to the bottom. This is further centrifuged and the percentage of the cells and liquid is determined.

3. Describe a red blood cell.

A red blood cell is a biconcave disk that has no nucleus.

4. Distinguish between oxyhemoglobin and deoxyhemoglobin.

Oxyhemoglobin is hemoglobin combined with oxygen. Deoxyhemoglobin is hemoglobin that has released its oxygen.

5. Explain what is meant by a red blood cell count.

A red blood cell count is the number of red blood cells in a cubic millimeter (mm3) of blood.

6. Describe the life cycle of a red blood cell.

a. Nutrients from food are absorbed from the small intestine into the bloodstream.

b. The blood transports the absorbed nutrients to the red bone marrow tissue.

c. The red bone marrow produces red blood cells.

d. The red blood cells circulate for about 120 days.

e. Damaged and old red blood cells are destroyed in the liver.

f. The resulting biliverdin is converted to bilirubin that is excreted in the bile from the liver.

7. Define erythropoietin, and explain its function.

Erythropoietin is a hormone that is released from the kidneys, and to a lesser extent the liver, which stimulates red blood cell production.

8. Explain how vitamin B12 and folic acid deficiencies affect red blood cell production.

Both substances are required for DNA synthesis that is needed by all cells for growth and reproduction.

Hematopoietic tissue reproduces at a particularly high rate, so this tissue is especially affected by the lack of either vitamin.

9. List two sources of iron that can be used for the synthesis of hemoglobin.

Obtaining vitamin C in the diet will increase iron absorption from the small intestine. It is also conserved from the red blood cell destruction and reused.

10. Distinguish between biliverdin and bilirubin.

Biliverdin is the greenish pigment that results when the heme portion of the hemoglobin breaks apart.

Bilirubin is what biliverdin eventually converts to over time.

11. Distinguish between granulocytes and agranulocytes.

A granulocyte is a white blood cell that has granular cytoplasm. Agranulocytes are white blood cells that lack cytoplasmic granules.

12. Name five types of leukocytes, and list the major functions of each type.

a. Neutrophils are granulocytes that function to phagocytize foreign particles.

b. Eosinophils are granulocytes that function to kill certain parasites and help control allergic reactions.

c. Basophils are granulocytes that function to release heparin that inhibits blood clotting. They also release histamine to cause inflammation.

d. Monocytes are agranulocytes that leave the bloodstream to function as macrophages that phagocytize foreign particles.

e. Lymphocytes are agranulocytes that function to produce antibodies that act against specific foreign substances.

13. Explain the significance of white blood cell counts as aids to diagnosing diseases.

If there is a rise in white blood cells, there could be an infection of some type going on within the body. If the white blood cell count drops, there could be an entirely different set of diseases that could be going on within the body. A differential white blood cell count measures the numbers of each specific type of white blood cell.

This can signal a specific disease process, as an increase in neutrophils usually means a bacterial infection.

14. Describe a blood platelet, and explain its functions.

A blood platelet (thrombocyte) is a fragment of a cell. They function to initiate the formation of blood clots.

15. Name three types of plasma proteins, and list the major functions of each type.

a. Albumins—help to maintain osmotic pressure of the blood.

b. Globulins—help to transmit lipids and fat-soluble vitamins and are the antibodies of immunity.

c. Fibrinogen—precursor to fibrin that has a major role in blood clotting.

16. Name the gases and nutrients in plasma.

Gases in plasma include oxygen, carbon dioxide, and nitrogen. Plasma nutrients include amino acids, simple sugars, and lipids.

17. Define nonprotein nitrogenous substances, and name those commonly present in plasma.

A nonprotein nitrogenous substance is a molecule that contains nitrogen atoms but are not proteins. Amino acids, urea, and uric acid are commonly present in the blood plasma.

18. Name several plasma electrolytes.

These include sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate ions.

19. Define hemostasis.

Hemostasis refers to the stoppage of bleeding.

20. Explain how blood vessel spasms are stimulated following an injury.

Cutting or breaking a blood vessel stimulates the smooth muscles in its wall to contract. This response may

only last a few minutes but as the platelet plug forms, serotonin is released, which causes the smooth muscles in the wall to contract further.

21. Explain how a platelet plug forms.

Platelets tend to stick to collagen fibers in connective tissue and any rough surface. They also begin to stick to each other, forming the platelet plug.

22. List the major steps leading to the formation of a blood clot.

a. The production of a substance called prothrombin activator. This is dependent upon the presence of calcium ions.

b. Tissue damage occurs and the clotting mechanism starts reactions, which also depend on the presence of calcium. This leads to production of prothrombin activator, which converts prothrombin into thrombin.

c. Thrombin acts as an enzyme and causes a reaction in fibrinogen allowing it to become fibrin.

d. The fibrin threads stick to the exposed surfaces of the damaged blood vessels and create a meshwork in

which various blood cells and platelets become entangled. The resulting mass is the blood clot.

23. Indicate the trigger and outline the steps for extrinsic clotting and intrinsic clotting.

The trigger for extrinsic clotting is the blood vessel wall or tissue outside the blood vessels contracting. The

steps that follow are what were outlined in question 27. The intrinsic clotting factors are all within the blood proper. The trigger is exposure of the blood to a foreign surface such as collagen. Factor XII (the Hageman factor) then activates factor XI, which in turn activates factor IX. Factor IX then joins with factor VIII and platelet phospholipids to activate factor X. These reactions, for which calcium is required, lead to the production of prothrombin activator. The extrinsic flow would follow as previously described.

24. Distinguish between fibrinogen and fibrin.

Fibrinogen is the soluble precursor to the insoluble fibrin.

25. Describe a positive feedback system that operates during blood clotting.

Once a blood clot starts to form, it promotes still more clotting. This is due to the fact that thrombin also acts directly on blood-clotting factors other than fibrinogen. It can cause prothrombin to form still more thrombin.

This is positive feedback.

26. Define serum.

Serum is essentially plasma minus all of its fibrinogen and most of the other clotting factors.

27. Distinguish between a thrombus and an embolus.

A thrombus is a blood clot that forms in a vessel abnormally. An embolus is a blood clot that becomes dislodged and is carried away by blood flow.

28. Explain how a blood clot may be removed naturally from a blood vessel.

Fibrin threads absorb a plasma protein called plasminogen. Then a substance called plasminogen activator is released from the lysosomes of the damaged tissue cells that converts plasminogen to plasmin. Plasmin is a protein-splitting enzyme that can digest fibrin threads and other proteins associated with blood clots.

29. Describe how blood coagulation may be prevented.

The endothelium of blood vessels discourages the accumulation of platelets and clotting factors. Endothelial cells also produce prostacyclin (PGI2), a prostaglandin, that inhibits adherence of platelets to the inner surface of blood vessel walls. Antithrombin that is present in the plasma globulins inactivates thrombin. Heparin is also released from mast cells and basophils, which interferes with the formation of prothrombin activator.

30. State a vitamin required for blood clotting.

Vitamin K is necessary for some clotting factors to function.

31. Distinguish between antigen and antibody.

An antigen that is present on the surface of red cell membranes. Antibodies are proteins that are dissolved in the plasma.

32. Explain the basis of ABO blood types.

The ABO blood types are based on the presence or absence of two major antigens (formerly called agglutinogens) on the red blood cells membranes. Their presence or absence is determined by heredity. The two antigens are antigen A and antigen B. The types of blood with the corresponding antigens are:

a. Type A—antigen A

b. Type B—antigen B

c. Type AB—antigen A and B

d. Type O—neither antigen A nor B

33. Explain why a person with the blood type AB is sometimes called a universal recipient.

Because blood type AB lacks both anti-A and anti-B antibodies, an AB person can receive blood of any type.

34. Explain why a person with blood type O is sometimes called a universal donor.

People with type O blood lack antigens A and B, which allows transfusion into persons with blood of any other type. Type O blood does contain both anti-A and anti-B antibodies so if transfused to another blood type, it should be given slowly to minimize the chance of an adverse reaction.

35. Distinguish between Rh-positive and Rh-negative blood.

Rh-positive blood is when the red blood cell membrane has Rh antigens (most importantly antigen D) present.

Rh-negative blood lacks the Rh antigens.

36. Describe how a person may become sensitized to Rh-positive blood.

A person may become sensitized to Rh-positive blood by receiving a transfusion.

37. Define erythroblastosis fetalis, and explain how this condition may develop.

Erythroblastosis fetalis is a condition where an Rh-positive fetus has come into contact with anti-Rh antibodies through breaks in the placental membrane. This only happens if the mother has previously had a

child that was Rh-positive. The baby’s blood may agglutinate after birth.

Chapter 14 out line

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I. Blood and Blood Cells

A. Introduction

1. Blood is three to four times more viscous than water.

2. Most blood cells form in red bone marrow.

3. Types of blood cells are red blood cells and white blood cells.

4. Cellular fragments of blood are platelets.

5. Formed elements of blood are the cells and platelets.

B. Blood Volume and Composition

1. Blood volume varies with body size, changes in fluid and electrolyte concentrations, and the amount of adipose tissue.

2. Blood volume is about 8% of body weight.

3. An average-size adult has 5 liters of blood.

4. Hematocrit is the percentage of blood cells in a blood sample.

5. A blood sample is usually 45 % red blood cells and 55 % plasma.

6. Plasma is a mixture of water, amino acids, proteins, carbohydrates, lipids, vitamins, hormone, electrolytes, and cellular wastes.

7. Less than 1% of formed elements of blood are white blood cells and platelets and 99% are red blood cells.

C. The Origin of Blood Cells

1. Blood cells originate in red bone marrow from hemocytoblasts or hemopoietic stem cells.

2. A stem cell can differentiate into any number of specialized cell types.

3. Colony-stimulating factors are growth factors that stimulate stem cells to produce certain cell types.

4. Thrombopoietin stimulates the production of megakaryocytes.

D. Characteristics of Red Blood Cells

1. Red blood cells are also called erythrocytes.

2. Red blood cells are biconcave in shape.

3. The biconcave shape of red blood cells allow them to have an increased surface area for the transport of gases.

4. Hemoglobin is an oxygen carrying protein in red blood cells.

5. Each red blood cell is about one-third hemoglobin by volume.

6. Oxyhemoblobin is hemoglobin combined with oxygen.

7. Deoxyhemoglobin is hemoglobin that has released oxygen.

8. Red blood cells extrude their nuclei as they mature.

9. Because red blood cells lack mitochondria they must produce ATP through glycolysis.

10. As red blood cells age, they become rigid and are more likely to be damaged and removed by enzymes in the liver and spleen.

E. Red Blood Cell Counts

1. A red blood cell count is the number of RBCs in one mm³ of blood.

2. A healthy adult male has a red blood cell count between 4,600,00-6,200,000 cells per mm³.

3. A healthy adult female has a red blood cell count between 4,200,000-5,400,000 cells per mm³.

4. A healthy child has a red blood cell count between 4,500,000-5,100,000 cells per mm³

5. The number of red blood cells reflects the blood’s oxygen carrying capacity.

F. Red Blood Cell Production and Its Control

1. Erythropoiesis is red blood cell production.

2. Initially, red blood cell formation occurs in the yolk sac, liver and spleen.

3. After an infant is born, red blood cells are produced almost exclusively in the red bone marrow.

4. Hemoctyoblasts in red bone marrow give rise to erythroblasts that give rise to erythrocytes.

5. Reticulocytes are immature red blood cells that still contain endoplasmic reticulum.

6. The average life span of a red blood cell is 120 days.

7. Erythropoietin controls red blood cell production and is released primarily from the kidneys.

8. When the availability of oxygen decreases, erythropoietin is released and red blood cell production increases.

G. Dietary Factors Affecting Red Blood Cell Production

1. Two vitamins needed for red blood cell production are vitamin B₁₂ and folic acid.

2. Two B-complex vitamins are needed for DNA synthesis.

3. Intrinsic factor is needed for the absorption of vitamin B₁₂.

4. Iron is required for hemoglobin production.

5. Anemia is a reduction in the oxygen-carrying capacity of the blood.

H. Destruction of Red Blood Cells

1. Damaged red blood cells rupture as they pass through the spleen or liver.

2. In the liver and spleen, macrophages destroy worn out red blood cells.

3. Hemoglobin molecules are broken down into globin and heme groups.

4. Heme decomposes into iron and biliverdin.

5. Ferritin is an iron-protein complex that stores iron in the liver.

6. Biliverdin is converted to bilirubin.

7. Bilirubin and biliverdin are excreted in bile.

8. The polypeptide globin chains breakdown into amino acids.

I. Types of White Blood Cells

1. White blood cells are also called leukocytes.

2. White blood cells function to protect against diseases.

3. Two hormones that stimulate white blood cell production are interleukins and CSFs.

4. Granulocytes have granules in their cytoplasm whereas agranulocytes lack cytoplasmic granules.

5. Examples of granulocytes are neutrophils, basophils, and eosinophils.

6. Neutrophil granules appear light purple in an acid/base stain.

7. Neutrophils have nuclei that are lobed.

8. Neutrophils phagocytize bacteria, fungi, and some viruses.

9. Neutrophils account for about 54%-62% of white blood cells in a blood sample.

10. Eosinophil granules stain red in an acid stain.

11. The nucleus of an eosinophil is usually bilobed.

12. Eosinophils moderate allergic reactions and defend against parasitic worm infestations.

13. Eosinophils make up 1%-3% of the total number of circulating white blood cells.

14. Basophil granules stain blue in a basic stain.

15. Basophils migrate to damaged tissues where they release histamine and heparin.

16. Histamine promotes inflammation.

17. Heparin functions to prevent blood clots.

18. Basophils usually account for less than 1% of leukocytes.

19. Examples of agranuloctyes are monocytes and lymphocytes.

20. The largest of the white blood cells are monocytes.

21. The nuclei of monocytes are spherical, kidney shaped or oval.

22. Monocytes can leave the blood stream to become macrophages.

23. Monocytes usually make up 3%-9% of white blood cells in a blood sample.

24. A typical lymphocyte contains a large, spherical nucleus surrounded by a thin rim of cytoplasm.

25. The major types of lymphocytes are T cells and B cells.

26. T cells attack microorganisms, tumor cells, and transplanted cells.

27. B cells produce antibodies.

28. Lymphocytes account for about 25%-33% of the circulating white blood cells.

J. Functions of White Blood Cells

1. Diapedesis is the movement of a WBC out of the blood stream into surrounding tissues.

2. Amoeboid motion is a form of self-propulsion used by WBCs outside the blood stream to move.

3. The most mobile and active phagocytic leukocytes are neutrophils and monocytes.

4. When microorganisms invade human tissues, basophils respond by releasing chemicals that dilate local blood vessels.

5. Positive chemotaxis is the attraction leukocytes have toward areas of damaged tissues.

6. Pus is an accumulation of bacteria, WBCs, and damaged cells.

K. White Blood Cell Counts

1. A white blood cell count is normally between 5,000-10,000 cells per mm³ of blood.

2. Leukocytosis is an increased WBC count and is often caused by acute infections.

3. Leukopenia is a decreased WBC count and is often caused by influenza, mumps, measles, chicken pox, or AIDS.

4. A differential white blood cell count lists percentages of the types of leukocytes in a blood sample.

5. The number of neutrophils increases during bacterial infections, and eosinophils increase during parasitic worm infections.

L. Blood Platelets

1. Platelets are also called thrombocytes.

2. Platelets arise from cells called megakaryocytes.

3. A normal platelet count is normally between 130,000-360,000 platelets per mm³ of blood.

4. Platelets help repair damaged blood vessels by sticking to broken surfaces.

5. Platelets release serotonin that contracts smooth muscles in the vessels walls, reducing blood flow.

II. Blood Plasma

A. Introduction

1. Plasma is the clear, straw-colored, liquid portion of the blood in which the cells and platelets are suspended.

2. About 92% of plasma is water.

3. Functions of plasma include transporting nutrients, gases and vitamins; helping to regulate fluid and electrolyte balance; and maintaining a favorable pH.

B. Plasma Proteins

1. The three main plasma protein groups are albumins, globulins, and fibrinogen.

2. Albumins are the smallest of the plasma proteins and are synthesized in the liver.

3. Albumins function to help maintain the colloid osmotic pressure of blood.

4. Colloid pressure is the osmotic pressure produced by plasma proteins.

5. Globulins can be divided into the following three groups: alpha, beta, and gamma globulins.

6. Alpha and beta globulins are synthesized in the liver and function to transport lipids and fat-soluble vitamins in the blood.

7. Gamma globulins are synthesized lymphatic tissues and function as constituents of antibodies.

8. Fibrinogen is synthesized in the liver and functions to promote blood clotting.

C. Gases and Nutrients

1. The most important blood gases are oxygen and carbon dioxide.

2. The plasma nutrients are amino acids, simple sugars, nucleotides, and lipids.

D. Nonprotein Nitrogenous Substances

1. Types of nonprotein nitrogenous substances in plasma are urea, uric acid, creatinine, and creatine.

2. Urea is produced when proteins are metabolized.

3. Uric acid is produced when nucleic acids are metabolized.

4. Creatinine is produced from metabolism of creatine.

5. Creatine phosphate is a protein that stores phosphate molecules for the production of ATP.

6. About half of the NPN substances in blood is urea.

E. Plasma Electrolytes

1. Plasma electrolytes include sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, and sulfate.

2. Sodium and chloride ions are the most abundant plasma electrolytes.

III. Hemostasis

A. Introduction

1. Hemostasis refers to the stoppage of bleeding.

2. Three actions that may prevent blood loss are blood vessel spasm, platelet plug formation, and blood coagulation.

B. Blood Vessel Spasm

1. Vasospasm is smooth muscle contraction in the wall of a blood vessel.

2. Following vasospasm, blood loss lessens and the ends of the severed vessel may close completely.

C. Platelet Plug Formation

1. Platelets adhere to exposed ends of injured blood vessels.

2. A platelet plug is formed when platelets contact collagen.

3. The function of the platelet plug is to prevent blood loss.

D. Blood Coagulation

1. Introduction

a. Coagulation causes the formation of a blood clot.

b. The extrinsic clotting mechanism is triggered by chemicals from broken blood vessels or damaged tissues.

c. The intrinsic clotting mechanism is triggered by the contact of blood with foreign surfaces in the absence of tissue damage.

d. Clotting factors are chemicals that control blood clotting.

e. Vitamin K is necessary for some clotting factors to function.

f. Procoagulants promote blood clotting and anticoagulants inhibit blood clotting.

g. Normally, anticoagulants prevail and the blood does not clot.

h. The major event in blood clot formation is conversion of fibrinogen into fibrin.

2. Extrinsic Clotting Mechanism

a. The extrinsic clotting mechanism is triggered when blood contacts damaged blood vessel walls or tissue outside blood vessels.

b. Tissue thromboplastin is a substance released from damaged tissue and activated clotting factor VII.

c. The series of reactions in the extrinsic clotting mechanism are dependent on calcium ions.

d. Prothrombin activator converts prothrombin to thrombin.

e. The function of thrombin is to convert fibrinogen to fibrin.

f. Once fibrin threads form, they stick to exposed surfaces of damaged blood vessels, creating a blood clot.

g. A blood clot is composed of fibrin threads that have trapped blood cells and platelets.

h. Blood clotting is enhanced by a positive feedback system.

i. Normally blood clot formation is prevented by blood flow.

3. Intrinsic Clotting Mechanism

a. The Hageman factor initiates clotting in the intrinsic clotting mechanism.

b. The intrinsic clotting mechanism occurs when blood is exposed to a foreign surface such as collagen in connective tissue.

c. The reactions of the intrinsic clotting mechanism depend on calcium ions.

d. Most of the steps of blood clot formation in the intrinsic clotting mechanism are the same as those of the extrinsic clotting mechanism.

4. Fate of Blood Clots

a. After a blood clot forms, it soon begins to retract.

b. Serum is plasma minus clotting factors.

c. Platelet-derived growth factor stimulates smooth muscle cells and fibroblasts to repair damaged blood vessel walls.

d. Fibroblasts produce fibers that help strengthen and seal vascular breaks.

e. Plasmin is released from blood clots and functions to break down blood clots.

f. A thrombus is an abnormal blood clot.

g. An embolus is a thrombus or portion of a thrombus that is moving in the blood stream.

h. Atherosclerosis is the accumulation of fatty deposits on the endothelium of blood vessels.

i. Thrombosis in veins is usually caused by atherosclerosis.

E. Prevention of Coagulation

1. The smooth lining of blood vessels discourages blood clot formation.

2. Prostacyclin inhibits the adherence of platelets to the inner surface of healthy blood vessel walls.

3. Antithrombin inactivates thrombin.

4. Heparin is an anticoagulant.

IV. Blood Groups and Transfusions

A. Antigens and Antibodies

1. Agglutination is the clumping of RBCs and is due to a reaction between RBC surface molecules called antigens and proteins called antibodies.

2. Avoiding the mixture of certain kinds of certain kinds of antibodies and antigens prevents adverse transfusion reactions.

B. ABO Blood Group

1. The ABO blood group is based on the presence or absence of antigen A and antigen B on RBC membranes.

2. A person with only antigen A has type A blood.

3. A person with only antigen B has type B blood.

4. A person with both antigen A and antigen B has type AB blood.

5. A person with neither antigen A nor antigen B has type O blood.

6. A person with type A blood has anti-B antibody in their plasma.

7. A person with type B blood has anti-A antibody in their plasma.

8. A person with type AB blood has neither anti-A nor anti-B antibodies in their plasma.

9. A person with type O blood has both anti-A and anti-B antibodies in their plasma.

10. Antibodies anti-A and anti-B do not cross the placenta.

11. The major concern in blood transfusion procedures is that the cells in the donated blood not clump due to antibodies present in the recipient’s plasma.

12. A person with type AB blood is called a universal recipient because type AB lacks both anti-A and anti-B antibodies, so a person with this blood type can receive blood from any other blood type.

13. Type O blood is the universal donor because it lacks antigens A and B, so this blood type can be given to persons of all other blood types.

14. A person with Type A blood cannot receive Type B blood because antibodies in the recipient’s plasma would destroy the RBCs of the donor blood.

C. Rh Blood Group

1. The Rh blood group was named after the Rhesus monkey.

2. Blood is said to be Rh positive when Rh antigens are present on RBCs.

3. Blood is said to be Rh negative when Rh antigens are not present on RBCs.

4. Anti-Rh antibodies form only in Rh-negative persons when the Rh negative person is exposed to Rh positive blood.

5. When an Rh-negative woman is pregnant with an Rh positive fetus, she will produce anti-Rh antibodies.

6. Erythroblastosis fetalis occurs when a woman has already developed anti-Rh antibodies and they cause hemolysis of the RBCs of the fetus.

Chapter 13 questions

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Endocrine System

1. What is an endocrine gland?

An endocrine gland is a gland that secretes its hormones directly into body fluids (the internal environment).

2. Define hormone and target cell.

A hormone is a secreted biochemical that affects the functions of another cell. A target cell is a cell that possesses specific receptors for a particular hormone. Thus, a hormone affects only its specific target cell.

3. Explain how hormones can be grouped on the basis of their chemical composition.

Hormones can be grouped into five separate categories:

Steroid—Steroid are lipids that are made of complex rings of carbon and hydrogen. They differ by the

types and numbers of atoms attached to these regions and by the way they are joined together.

Amines—Amines are hormones produced by neurons and the adrenal medulla. These include epinephrine and norepinephrine.

Peptides—Peptides are short chains of amino acids.

Proteins—Proteins are composed of many linked amino acids forming complex chains.

Glycoproteins—Glycoproteins are proteins joined to a carbohydrate.

Prostaglandins are not true hormones. These substances however, do have regulating effects on neighboring cells.

4. Explain how steroid hormones influence cells.

Steroid hormones, along with thyroid hormones, are soluble lipids that enter target cells easily by diffusion.

Once inside, they enter the nucleus and combine with nuclear protein receptors. This hormone-receptor

complex binds to a particular section of DNA and activates specific genes. These active genes are transcribed onto MRNA that directs manufacture of specific proteins. These proteins, in turn, cause the cellular changes intended by the original hormone.

5. Distinguish between the binding site and the activity site of a receptor molecule.

The binding site of a cell is the place where a specific substance adheres to its receptor. Once joined, the

binding site stimulates the activity site, where other membrane proteins may alter the functions of various

enzymes or transport mechanisms.

6. Explain how nonsteroid hormones may function through the formation of cAMP.

In some cells, the activity site activates a molecule called a G protein. This protein then activates adenylate

cyclase, an enzyme bound to the inside of the cell membrane. Adenylate cyclase removes two phosphates from ATP and forms the AMP (adenosine monophosphate) into a circle. The cyclic AMP (cAMP) activates protein kinases that remove phosphate molecules from the other ATP molecules and join them to certain protein substrates. These alter protein substrates then induce the various changes in the cell’s metabolism.

7. Explain how nonsteroid hormones may function through an increase in intracellular calcium ion concentration.

Some nonsteroid hormones stimulate the activity of sites of their target cells to cause an increase in the transport of calcium ions from outside, or release of calcium ions from cellular storage sites. The calcium

combines with calmodulin (a protein) and activates it. The activated calmodulin alters the function of various enzymes to produce the desired effect.

8. Explain how the cellular response to a hormone operating through a second messenger is amplified.

Unlike the steroid hormones that rely on direct effects, the second messenger mechanism allows many second messenger molecules to be manufactured for each hormone-receptor complex formed. This yields a high effect with a small amount of hormone molecules. Because of this mechanism, cells are highly sensitive to nonsteroid hormone concentration.

9. Define prostaglandins, and explain their general function.

Prostaglandins are paracrine substances that are very potent and are only synthesized just before they are released. They are then rapidly inactivated. Some prostaglandins regulate response to hormones by either

activating or inactivating cAMP production. Others can relax smooth muscle in the airway passages and blood vessels, casing dilation. Still others contract smooth muscle in the uterus causing menstrual cramps and labor contractions. Prostaglandins can also stimulate secretion of hormones from the adrenal cortex and inhibit secretion of hydrochloric acid in the stomach. Prostaglandins also influence sodium ion movement and water in the kidneys, regulate blood pressure, have power effects on reproductive physiology, and promote inflammation in damaged tissues.

10. Describe a negative feedback system.

In the negative feedback system, an endocrine gland or controlling system is sensitive to the concentration of substances it regulates or of a product it controls. When the concentration increases to a certain level, the gland is inhibited (a negative effect), and its activity decreases. When the concentration decreases to a certain level, the gland is no longer inhibited and its production increases. The rapid response of this system keeps hormone levels relatively stable.

11. Define releasing hormone, and provide an example of one.

Releasing hormones stimulate other endocrine glands to release their hormones. An example is the trophic hormones of the anterior pituitary glands that are ultimately controlled by the hypothalamus.

12. Describe the location and structure of the pituitary gland.

The pituitary gland (hypophysis) is about one centimeter in diameter and is attached to the hypothalamus at the base of the brain by the infundibulum. It is surrounded and protected by the sella turcica of the sphenoid bone. The pituitary gland is divided into two distinct lobes: the anterior (adenohypophysis) and the posterior (neurohypophysis).

13. List the hormones the anterior pituitary gland secretes.

The anterior pituitary gland secretes growth hormone (GH), thyroid stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL).

14. Explain how the brain controls pituitary gland activity.

The posterior lobe of the pituitary responds to nerve impulses from the hypothalamus. Primarily the releasing hormones from the hypothalamus control the anterior lobe of the pituitary. It does this by sending the releasing hormones in the blood through a capillary network in the hypothalamus, which merges to form the hypophyseal portal veins. It passes downward into the capillary network in the anterior lobe. Substances released from the hypothalamus are sent directly to the anterior lobe.

15. Explain how growth hormone produces its effects.

Growth hormone (GH), or somatotropin (STH), is a protein that causes cells to increase in size and mitotic rate. It increases protein synthesis and amino acid movement through cell membranes. GH also increases cellular respiration of fats by decreasing metabolism of carbohydrates.

16. List the major factors that affect growth hormone and secretion.

Growth hormone is especially secreted during sleep, and during low blood concentrations of proteins and glucose.

17. Summarize the functions of prolactin.

Prolactin (PRL) primarily promotes milk production in females. In males, it decreases secretion of luteinizing hormone (LH), thus causing a decrease in the production of androgens. If PRL production is excessive in the male, it may cause infertility.

18. Describe regulation of concentrations of circulating thyroid hormones.

Thyroid hormones are regulated by several factors. The most direct control is from thyroid stimulating hormone (TSH) from the anterior pituitary. TSH can also stimulate growth of the thyroid gland. Another

factor is the hypothalamus. It secretes thyrotropin releasing hormone (TRH), which stimulates TSH release.

External factors regulating thyroid hormone include extreme cold and emotional stress.

19. Explain the control of secretion of ACTH.

Adrenocorticotropic hormone (ACTH) is regulated in part by corticotropin releasing hormone (CRH) from the hypothalamus in response to low levels of adrenal cortical hormones. Stress increases secretion of ACTH by stimulating CRH production.

20. List the major gonadotropins, and explain the general functions of each.

The major gonadotropins are:

Follicle stimulating hormone (FSH)—FSH is responsible for growth and development of follicles in the

ovaries and stimulates these cells to secrete estrogen. In males, it stimulates the production of sperm cells at puberty.

Luteinizing hormone (LH)—LH promotes secretions of both male and female sex hormones. It is necessary for the release of egg cells from the ovaries. In males, LH is known as interstitial cell stimulating hormone (ICSH) because it acts on the interstitial cells of the testes.

21. Compare the cellular structures of the anterior and posterior lobes of the pituitary gland.

The anterior lobe is composed of layers of epithelial tissues grouped around many blood vessels. The epithelial tissues contain five types of secretory cells responsible for hormone production: mammatropes, somatotropes, thyrotropes, corticotropes, and gonadotropes. The posterior pituitary lobe is made of pituicytes and nerve fibers originating in the hypothalamus.

22. Name the hormones associated with the posterior pituitary, and explain their functions.

Special neurons in the hypothalamus actually produce the two hormones associated with the posterior pituitary lobe. These hormones are stored in secretory granules at the ends of their axons, in the posterior pituitary lobe.

The two hormones are:

Antidiuretic hormone (ADH)—ADH is a short polypeptide that inhibits water excretion from the kidneys.

ADH can also have a contracting effect on blood vessels. This can cause a rise in blood pressure. This is especially important in cases of severe blood loss, when ADH is needed to help increase vascular resistance.

For this reason, ADH is sometimes called vasopressin.

Oxytocin (OT)—OT is a short polypeptide that is responsible for uterine contractions of labor in childbirth and contracting cells of milk glands in lactating breasts so that milk is forced out during suckling. To a lesser extend, OT can play a role in antidiuretic mechanisms.

23. Explain how the release of ADH is regulated.

The hypothalamus contains osmoreceptors that sense changes in blood solute levels. If the solute

concentration increases due to a lack of fluids, the hypothalamus signals the release of ADH from the posterior pituitary into the blood stream. In the kidneys, this causes water to be saved internally. If solute concentration decreases, the hypothalamus inhibits ADH secretion, causing the kidneys to excrete more water. Certain blood vessels contain volume receptors that sense how much a vessel is stretched by blood. When the volume is too great, ADH secretion is inhibited. When the volume is too low, as from hemorrhage, ADH secretion is increased, causing the kidneys to retain water.

24. Describe the location and structure of the thyroid gland.

The thyroid gland consists of two large lobes connected by a broad isthmus. It is found just inferior to the larynx, bilaterally and anterior to the trachea. It is a very vascular structure encapsulated in connective tissue.

The gland is composed of many secretory follicles. The follicles are lined with a single layer of cuboidal

epithelium and are filled with a clear viscous glycoprotein called colloid. Extrafollicular cells (C cells) are

found just outside the follicles.

25. Name the hormones the thyroid gland secretes, and list the general functions of each.

The thyroid gland secretes the following hormones:

Thyroxine—Thyroxine is also known as tetraiodothyronine (T4). It helps regulate metabolism of carbohydrates, lipids, and proteins.

Triiodothyronine (T3)—Triiodothyronine also serves to regulate metabolism of carbohydrates, lipids, and proteins.

Calcitonin—Calcitonin is synthesized by the C cells and influences blood calcium and phosphate concentrations.

26. Define iodine pump.

The follicular cells of the thyroid gland require iodine salts (iodides) to produce T3 and T4. After the iodides have been absorbed from the intestine, the blood carries them to an active transport mechanism in the thyroid, called the iodine pump. This pump concentrates the iodides into the follicular cells where they combine with tyrosine in the synthesis of thyroid hormones.

27. Describe the location and structure of the parathyroid glands.

The four parathyroid glands are located on the posterior surface of the thyroid gland, two on each side, arranged in a superior-inferior fashion. The parathyroid gland is a small yellowish-brown structure composed of many tightly packed secretory cells encapsulated in a connective tissue layer.

28. Explain the general functions of parathyroid hormone.

Parathyroid hormone (PTH) is also called parathormone. It is a protein that increases blood calcium ion

levels and decreases blood phosphate ion levels by acting on the bones, kidneys, and intestines.

29. Describe the mechanisms that regulate the secretion of parathyroid hormone.

Parathyroid hormone (PTH) is controlled by a negative feedback system between the parathyroid glands and the concentration of blood calcium ions. If blood calcium ion concentration is high, PTH secretion is inhibited.

If blood calcium ion concentration is low, PTH secretion is increased. This causes bone resorption by osteocytes and osteoclasts which releases both calcium and phosphate ions into the blood stream.

Simultaneously, PTH causes the kidneys to keep calcium ions and excrete phosphate ions. Indirectly, PTH

causes increased absorption of calcium ions from food in the intestines by influencing vitamin D metabolism.

30. Distinguish between the adrenal medulla and the adrenal cortex.

The adrenal medulla is the central portion of an adrenal gland and consists of irregularly shaped cells grouped around blood vessels. These cells are modified postganglionic neurons that are directly linked to the preganglionic autonomic nerve fibers leading from the central nervous system. The adrenal cortex is the outermost part of an adrenal gland and makes up the bulk of the gland. It is made of closely packed masses of epithelial layers that form three distinct zones: the zona glomerulosa, zona fasiculata, and zona reticularis—the outer, middle, and inner layers, respectively.

31. List the hormones produced by the adrenal medulla, and describe their general functions.

The adrenal medulla produces, stores, and secretes two hormone—epinephrine (adrenaline) and

norepinephrine (noradrenaline). Both are catacholamines and have similar functions. Their effects include:

increased heart rate and cardiac muscle contractile force, elevated blood pressure, increased respirations, and decreased digestive system activity. Both hormones act simultaneously with the sympathetic nervous system in the “fight-or-flight” response.

32. List the steps in the synthesis of adrenal medullary hormones.

The synthesis of epinephrine and norepinephrine begins with the amino acid tyrosine. First, the enzyme

tyrosine hydroxylase converts tyrosine into dopa. Then, the enzyme dopa decarboxylase converts dopa into dopamine. Next, dopamine beta hydroxylase converts dopamine into norepinephrine. About 85% of

norepinephrine is converted by the enzyme phenylethanolamine N-methyltransferase into epinephrine.

33. Name the most important hormones of the adrenal cortex, and describe the general functions of each.

Although the cells of the adrenal cortex produce more than thirty different steroids, there are three cortical hormones without which the body cannot survive. These are:

Aldosterone—Aldosterone is a mineralcorticoid that is responsible for regulation of mineral electrolytes by conserving sodium ions and excreting potassium ions.

Cortisol (hydrocortisone)—Cortisol is a glucocorticoid that is responsible for glucose metabolism between meals by regulating synthesis of glucose from noncarbohydrates. It also decreases protein synthesis and increases fatty acid release.

Adrenal Androgens—Adrenal androgens are sex hormones. Some are converted into estrogens by the skin, liver, and adipose tissues. These hormones supplement the supply of sex hormones from the gonads and stimulate early development of reproductive organs.

34. Describe the regulation of the secretion of aldosterone.

When the adrenal cortex responds directly to changes in the concentration of potassium ions in blood plasma, it only slightly responds to a decrease in plasma sodium ions. Aldosterone secretions is indirectly regulated by juxtaglomerular cells in the kidneys that respond to changes in blood pressure and plasma sodium concentration. If either of these decreases, the juxtaglomerular cells release the enzyme renin. This enzyme decomposes the blood protein angiotensinongen, thus causing the release of the peptide angiotensin I. In the lungs, angiotensin I is converted into angiotensin II by the enzyme angiotensin-converting enzyme (ACE).

When angiotensin II is carried to the adrenal cortex by the blood stream, it stimulates secretion of aldosterone.

ACTH stimulates aldosterone secretion in response to other stimuli.

35. Describe control of cortisol secretion.

Cortisol is regulated by a negative feedback system. In response to increased glucose levels, the hypothalamus secretes CRH. This stimulates the anterior pituitary gland to secrete ACTH. The ACTH stimulates the adrenal cortex to secrete cortisol. As cortisol concentration increases, ACTH and CRH secretion decreases.

36. Describe the location and structure of the pancreas.

The pancreas is an elongated, flattened organ posterior to the stomach and the parietal peritoneum, and is attached to the duodenum by a duct. Structurally, the pancreas is composed of grouped cells called islets of Langerhans that are closely associated with blood vessels. The islets of Langerhans contain three types of

cells: alpha, beta, and delta cells.

37. List the hormones the pancreatic islets secrete, and describe the general functions of each.

Glucagon—Glucagon is a protein secreted by alpha cells and is responsible for converting glycogen into glucose (glycogenolysis) in the liver, and noncarbohydrates into glucose (gluconeogenesis). Glucagon also stimulates the breakdown of fats into fatty acids and glycerol.

Insulin—Insulin is a protein secreted by beta cells that has the opposite effect of glucagon. In the liver, it

stimulates formation of glycogen and inhibits conversion of noncarbohydrates. Insulin also promotes facilitated diffusion of glucose through the membranes of insulin target cells.

Somatostatin—Somatostatin is secreted by delta cells and inhibits glucagon and insulin secretion and helps regulate carbohydrates.

38. Summarize how the secretion of hormones from the pancreas is regulated.

Glucagon and insulin are controlled by negative feedback systems sensitive to blood protein concentration.

Glucagon release is stimulated when a low concentration of blood sugar is detected and inhibited as blood

sugar concentration rises. Insulin release is stimulated when blood glucose concentration becomes too high. As blood glucose level concentration falls, insulin release is inhibited. Insulin and glucagon function together at various levels to keep blood glucose concentration relatively constant.

39. Describe the location and general function of the pineal gland.

The pineal gland is small and oval, found deep between the cerebral hemispheres, and attached to the upper portion of the thalamus near the roof of the third ventricle. It is made up of pineal and neuroglial cells. The pineal gland secretes melatonin in response to periods of decreased light. It is believed that this aids in the regulation of circadian rhythms and inhibiting gonadotropins from the anterior pituitary gland. It may also help to regulate menstrual cycles.

40. Describe the location and general function of the thymus gland.

The thymus gland begins in childhood as a large substernal gland found in the mediastinum between the

lungs, but diminishes in size with age. It plays an important role in immunity by secreting a group of hormones called thymosins that affect production of T lymphocytes (white blood cells).

41. Distinguish between a stressor and stress.

Stress is a condition in which potentially life-threatening changes occur in the body’s internal environment. To maintain homeostasis, the body must react to counter these changes. A stressor is any factor that can cause these conditions.

42. List several factors that cause physical and psychological stress.

Extreme temperatures, decreased oxygen, infection, injuries, heavy exercise, and loud noise can cause physical stress. Psychological stress differs from person to person but typically includes personal loss, thoughts of real or imagined dangers, unpleasant or lack of social interaction, anger, fear, grief, anxiety, depression, or guilt.

Occasionally even pleasant stimuli, such as friendly contact, joy or happiness, or sexual arousal, may cause stress.

43. Describe the general stress syndrome.

The general stress (or general adaptation) syndrome is controlled by the hypothalamus, and is the body’s response to stress. During stress, the hypothalamus stimulates the sympathetic nervous system’s “fight-or-flight” response by raising blood glucose, glycerol, and fatty acid concentrations, increasing heart rate, blood pressure, and breathing, and dilating air passages. It shunts blood away from the skin and digestive organs and redirects it into the skeletal muscles. It also increases epinephrine secretion and releases CRH to stimulate the anterior pituitary gland to secrete ACTH that, in turn, causes increased cortisol secretion from the adrenal cortex. Stress may also stimulate release of glucagon, GH, and ADH.

44. Which components of the endocrine system change the most as a person ages?

Endocrine glands tend to shrink and accumulate fibrous connective tissue, fat, and lipofuscin, but hormonal

activities usually remain within the normal range.

GH levels even out, as muscular strength declines.

ADH levels increase due to slowed breakdown.

The thyroid shrinks but control of metabolism continues.

Decreasing levels of calcitonin and parathyroid hormone increase osteoporosis risk.

The adrenal glands show aging-related changes, but negative feedback maintains functions.

Muscle, liver, and fat cells may develop insulin resistance.

Changes in melatonin secretion affect the body clock.

Thymosin production declines, hampering infectious disease resistance.

Chapter 13 out line

2007-12-06T14:30:00.002-08:00

I. General Characteristics of the Endocrine System

A. The endocrine glands secrete hormones.

B. Hormones diffuse from interstitial fluids into the blood stream and eventually act on target cells.

C. Paracrine secretions are secretions that do not travel in the blood stream to their targets.

D. Autocrine secretions are secretions that affect the secreting cell itself.

E. Exocrine glands secrete substances into ducts.

F. Endocrine glands and their hormones control metabolic processes.

G. Endocrine hormones also play vital roles in reproduction, development, and growth.

H. The larger endocrine glands are the pituitary, thyroid, parathyroids, adrenals, and pancreas.

II. Hormone Action

A. Introduction

1. Hormones are released into the extracellular spaces surrounding endocrine cells.

2. They diffuse into the bloodstream and are carried to all parts of the body.

B. Chemistry of Hormones

1. Introduction

a. Most hormones are either steroids or steroid-like substances or nonsteroids.

b. Nonsteroid hormones include amines, peptides, proteins, and glycoprotiens.

2. Steroid Hormones

a. Steroids are lipids that include complex rings of carbon and hydrogen atoms.

b. Examples of steroid hormones are testosterone, estrogen, aldosterone, and cortisol.

3. Nonsteroid Hormones

a. Examples of hormones called amines are norepinephrine and epinephrine.

b. Protein hormones are composed of long chains of amino acids.

c. Examples of protein hormones are those secreted by the anterior pituitary and parathyroid glands.

d. Hormones called glycoproteins are produced by the anterior pituitary.

e. Peptide hormones are short chains of amino acids.

f. Peptide hormones come from the posterior pituitary and hypothalamus.

g. Prostaglandins are paracrine substances and are produced in a wide variety of cells.

C. Actions of Hormones

1. Introduction

a. Hormones exert their effects by altering metabolic processes.

b. The more receptors the hormone binds on its target cell, the greater the response.

c. Up-regulation is an increase in the number of receptors on a target cell.

2. Steroid Hormones and Thyroid Hormones

a. Steroid and thyroid hormones are insoluble in water but are soluble in lipids.

b. Steroid and thyroid hormones can diffuse into cells relatively easily.

c. Once steroid and thyroid hormones are inside a cell, they combine with specific protein receptors located usually in the nucleus.

d. The binding of these hormones to the receptor usually activates or inhibits a gene.

e. Activated genes code for specific proteins.

f. The new proteins may be enzymes, transport proteins, or hormone receptors and they bring about cellular changes.

3. Nonsteroid Hormones

a. A nonsteroid hormone usually binds with receptors located on the cell membrane.

b. When a nonsteroid hormone binds to a membrane receptor, this causes the receptor’s activity site to interact with other membrane proteins.

c. Receptor binding may alter the function of enzymes or membrane transport mechanisms, changing the concentrations of still other cellular components.

d. A first messenger is the hormone that triggers a cascade of biochemical activity.

e. Second messengers are the chemicals in the cell that induce the changes that are recognized as responses to the hormone.

f. Many hormones use cyclic AMP as a second messenger.

g. G proteins are activated by the binding of a hormone to a membrane receptor.

h. Adenylate cyclase is activated by G proteins.

i. Adenylate cyclase functions to form cyclic AMP from ATP.

j. Cyclic AMP activates another set of enzymes called protein kinases.

k. Protein kinases function to transfer phosphate groups from ATP to proteins substrate molecules.

l. Phosphorylated substrates may be converted from inactive to active forms.

m. Activated proteins then alter various cellular processes to bring about the effect of that particular hormone.

n. Cellular responses to second messenger activation include altering membrane permeabilities, activating enzymes, promoting synthesis of certain proteins, stimulating or inhibiting metabolic pathways, promoting cellular movements, and initiating secretion of hormones and other substances.

o. Hormones whose actions require cyclic AMP include releasing-hormones from the hypothalamus, TSH, ACTH, FSH, LH, ADH, PTH, norepinephrine, epinephrine, glucagon, and calcitonin.

p. An example of another second messenger is DAG.

q. In another mechanism, a hormone binding its receptor increases calcium, ion concentration within the target cell.

r. Calcium ions bind to the protein calmodulin to activate it.

s. Activated calmodulin functions to interact with enzymes, altering their activities.

t. Cells are highly sensitive to changes in concentration of nonsteroid hormones because responses to them is greatly amplified through second messengers.

D. Prostaglandins

1. Prostaglandins are paracrine substances that act locally.

2. Some prostaglandins regulate cellular responses to hormones.

3. The variety of effects prostaglandins can produce include relaxation of smooth muscle in airway and blood vessels, contraction of smooth muscle in the uterus, stimulation of secretion of various hormones, and promotion of inflammation.

III. Control of Hormonal Secretions

A. Introduction

1. Hormones with short half-lives control body functions that turn on and off quickly.

2. Hormones are continually excreted in urine and broken down by enzymes in the liver.

3. Increasing or decreasing blood levels of hormones requires increased or decreased secretion.

B. Control Sources

1. Control of hormone secretion is essential to maintaining the internal environment.

2. The hypothalamus controls the anterior pituitary gland’s release of tropic hormones.

3. Tropic hormones stimulate other endocrine glands to release hormones.

4. An example of an endocrine organ directly stimulated by the nervous system is the adrenal medulla.

5. Some endocrine glands respond to changes in the composition of the internal environment.

5. As a result of negative feedback mechanisms, hormone levels remain relatively stable.

IV. Pituitary Gland

A. Introduction

1. The pituitary gland is located at the base of the brain.

2. The infundibulum is a stalk that attaches the pituitary gland to the hypothalamus.

3. The two portions of the pituitary are anterior and posterior.

4. The anterior lobe secretes the following hormones: GH, TSH, ACTH, FSH, LH, PRL.

5. The posterior pituitary secretes the following hormones: OT and ADH

6. The hypothalamus controls most of the pituitary gland’s activities.

7. The posterior pituitary receives impulses from the hypothalamus.

8. Releasing hormones from the hypothalamus control the anterior pituitary.

9. The hypophyseal portal veins are vessels that pass downward along the pituitary stalk from the hypothalamus and give rise to a capillary bed in the anterior lobe of the pituitary.

B. Anterior Pituitary Hormones

1. Somatotropes secrete GH.

2. Mammotropes secrete PRL.

3. Thyrotropes secrete TSH.

4. Corticotropes secrete ACTH.

5. Gonadotropes secrete FSH and LH.

6. Actions of growth hormone are stimulation of cells to enlarge and more rapidly divide, enhance movement of amino acids through the cell membranes, and increases the rate of protein synthesis. GH also decreases the rate as which cells utilize carbohydrates and increases the rate at which cells use fats.

7. The secretion of GH is controlled by somatostatin and GHRH.

8. Actions of prolactin are to sustain mild production after birth and to amplify effect of LH in males.

9. The secretion of PRL is under inhibitory control by PIH and PRF.

10. Actions of thyroid-stimulating hormone are to stimulate the thyroid gland to release its hormones.

11. The secretion of TSH is controlled by TRH.

12. The actions of adrenocorticotropic hormone are to control secretion of certain hormone from the adrenal cortex.

13. The secretion of ACTH is controlled by CRH.

14. Gonadotropins are LH and FSH.

15. The actions of follicle-stimulating hormone are to promote development of egg-containing follicles in ovaries, to stimulate follicular cells to release estrogen, and in males, to stimulate production of sperm cells.

16. The actions of luteinizing hormone are to promote secretion of sex hormones and to promote the release egg cells in females.

17. The secretion of FSH and LH is controlled by GnRH.

C. Posterior Pituitary Hormones

1. The posterior pituitary consists of nerve fibers and neuroglial cells.

2. Specialized neurons in the hypothalamus produce two hormones called OT and ADH.

3. The hormones produced in the hypothalamus travel down axons through the pituitary stalk to the posterior pituitary.

4. The actions of antidiuretic hormone are to cause a reduction in water excretion, and to raise blood pressure.

5. The secretion of ADH is controlled by blood water concentration and blood volume.

6. The actions of oxytocin are to contact muscles in uterine wall and to contract muscles associated with milk-secreting cells.

7. The secretion of oxytocin is controlled by uterine stretch and stimulation of breasts.

V. Thyroid Gland

A. Introduction

1. The thyroid gland consists of two lobes.

2. The thyroid gland is located just below the larynx on either side and anterior to the trachea.

B. Structure of the Gland

1. Follicles are secretory parts of the thyroid gland.

2. Colloid is a viscous fluid that fills follicles and contains thyroglobulin.

3. Thyroglobulin is a glycoprotein.

4. Extrafollicular cells are located outside of follicles.

5. The follicular cells produce hormones.

C. Thyroid Hormones

1. The three hormones produced by the thyroid gland are T₄, T₃, and calcitonin.

2. The actions of thyroxine and triiodothyronine are to regulate metabolism of carbohydrates, lipids, and proteins.

3. The secretion of T₃ and T₄ are controlled by TSH.

4. Follicular cells require iodine to produce T₃ and T₄.

5. The actions of calcitonin are to lower blood calcium levels.

6. The secretion of calcitonin is controlled by blood calcium levels. It is released in response to high blood calcium levels.

VII. Parathyroid Glands

A. Introduction

1. Parathyroid glands are located embedded in the thyroid gland.

2. Usually a person has four parathyroid glands.

B. Structure of the Glands

1. Each parathyroid gland is covered by a thin capsule.

2. The body of a parathyroid gland consists of many tightly packed secretory cells.

C. Parathyroid Hormone

1. The actions of PTH are to raise blood calcium levels.

2. The secretion of PTH is controlled by blood calcium levels. It is released in response to low blood calcium levels.

VIII. Adrenal Glands

A. Structure of the Glands

1. The adrenal glands are shaped like pyramids.

2. The two parts of an adrenal gland are the cortex and medulla.

3. The adrenal medulla consists of irregularly shaped cells grouped around blood vessels.

4. The adrenal cortex is composed of closely packed masses of epithelial layers.

5. The three layers of the adrenal cortex are the outer zona glomerulosa, the middle zona fasciculata, and the inner zona reticularis.

B. Hormones of the Adrenal Medulla

1. The two hormones released by the adrenal medulla are epinephrine and norepinephrine.

2. The actions of epinephrine and norepinephrine are increased heart rate, increased force of cardiac muscle contraction, elevated blood pressure, increased breathing rate and decreased activity of the digestive system

3. The secretion of epinephrine and norepinephrine are controlled by the sympathetic nervous system.

C. Hormones of the Adrenal Cortex

1. Introduction

a. The adrenal cortex produces more than 30 different steroids.

b. The most important adrenal cortical hormones are aldosterone, cortisol, and certain sex hormones.

2. Aldosterone

a. Aldosterone is secreted by the zona glomerulosa and is called a mineralocorticoid because it helps regulate the concentration of mineral electrolytes.

b. The actions of aldosterone are regulation of concentration of extracellular electrolytes by conserving sodium ions and excreting potassium ions.

c. The secretion of aldosterone is controlled by electrolyte concentrations in body fluids and the renin-angiotensin mechanism.

3. Cortisol

a. Cortisol is secreted by the zona fasciculata and is called a glucocorticoid because it affects glucose metabolism

b. The actions of cortisol are to decrease protein synthesis, increase fatty acid release, and simulate glucose synthesis from noncarbohydrates.
c. The secretion of cortisol is controlled by CRH.

4. Sex Hormones

a. The sex hormones are secreted by the zona reticularis.

b. The actions of the sex hormones are to supplement sex hormones from the gonads.

c. Examples of sex hormones are androgens such as testosterone.

IX. Pancreas

A. Structure of the Gland

1. The pancreas is located posterior to the stomach.

2. The endocrine portion of the pancreas consists of islets of Langerhans which are also called pancreatic islets.

3. Three cell types of the pancreatic islets are alpha, beta, and delta.

4. Alpha cells secrete glucagon.

5. Beta cells secrete insulin.

6. Delta cells secrete somatostatin.

B. Hormones of the Pancreatic Islets

1. The actions of glucagon are to stimulate the liver to break down glycogen and to convert noncarbohydrates into glucose. It also simulates the breakdown of fats.

2. The secretion of glucagon is controlled by blood glucose concentrations.

3. The actions of insulin are to promote the formation of glycogen from glucose, to inhibit conversion of noncarbohydrates into glucose, and to enhance movement of glucose through adipose and muscle cell membranes. It also decreases blood glucose concentrations, promotes transport of amino acids into cells, and enhances synthesis of proteins and fats.

4. The secretion of insulin is controlled by blood glucose concentrations.

5. The function of somatostatin is to help regulate carbohydrates.

X. Other Endocrine Glands

A. The pineal gland is located near the roof of the third ventricle deep in the cerebral hemispheres.

B. The pineal gland produces the hormone melatonin.

C. The functions of melatonin are to help regulate circadian rhythms and to inhibit secretion of gonadotropins.

D. The thymus gland is located between the lungs.

E. The thymus gland secretes a group of hormones called thymosins.

F. The function of thymosin is to promote the maturation of T lymphocytes.

G. Reproductive organs that secrete hormones are ovaries and testes.

H. Examples of hormones produced by reproductive organs are estrogen, progesterone, and testosterone.

I. The hormone produced by the heart is ANP.

J. The hormone produced by the kidneys is erythropoietin.

XI. Stress and Its Effects

A. Introduction

1. A stressor is a factor capable of producing stress.

2. Stress is a protective response produced by the body in response to stress factors.

B. Types of Stress

1. Examples of physical stress include extreme cold or heat, decreases oxygen concentrations, infection, injuries, heavy exercise and loud sounds.

2. Examples of psychological stress are imagined dangers, personal losses, unpleasant social interaction or any factor that threatens a person.

C. Responses to Stress

1. The general stress syndrome is a group of symptoms produced by the hypothalamus in response to stress.

2. Major events of the general stress syndrome are increased blood glucose levels, increased heart rate and breathing rate, dilation of airways, and shunting of blood into muscles. See table 13.13.

XII. Life-Span Changes

A. General changes in the glands of the endocrine system are a decrease in size and increase in the proportion of each gland that is fibrous in nature.

B. Treatments for endocrine disorders include supplements of hormones or removing part of an overactive gland or using drugs to block the action of an overabundant hormone.

C. Levels of ADH increase with age and as a result, the kidneys reabsorb more water.

D. The decrease of calcitonin levels with age increases the risk of osteoporosis.

E. The most obvious changes in endocrine function involve blood glucose regulation.