Chap 24

Question 0

2. The outer layer of the digestive tract is known as the

Answer 0

serosa

Question 1

1. The enzymatic breakdown of large molecules into their basic building blocks is called.

Answer 1

chemical digestion

Question 2

3. Double sheets of peritoneum that provide support and stability for the organs of the peritoneal cavity are the

Answer 2

mesenteries

Question 3

4. A branch of the portal vein, hepatic artery, and tributary of the bile duct form

Answer 3

a portal area

Question 4

5. Label the digestive system

Answer 4

a) oral cavity, teeth, tongue;
b) liver;
c) gallblader
d) pancreas
e) large intestine
f) salivary glands
g) pharynx
h) esophagus
i) stomach
j) small intestine
k) anus

Question 5

6. label

Answer 5

a) mucosa - mucous membrane - contain lamina propria - smooth muscle cells - secretory cells of mucous glands.
b) submucosa - submucosa plexus contains intrinsic nerve fibers and scattered neurons.
c) muscularis externa - also called muscularis - smooth muscle -
d) serosa -

Question 6

7. Most of the digestive tract is lined by ______________ epithelim

Answer 6

simple columar

Question 7

8. Regional movements that occur in the small intestine and function to churn and fragment the digestive material are called

Answer 7

segmentation - most areas of the small intestine and some portions of the large intestine undergo cycles of contraction that churn and fragment the bolus, mixing the contents with intestinal secretions. This activity, called segmentation does not push materials along the tract in any one direction.

Question 8

9. Bile release from the gallbladder into the duodenum occurs only under the stimulation of

Answer 8

cholecystokinin

Question 9

10. Label the three segments of the small intestine in the following figure.

Answer 9

a) duodenum
b) jejunum
c) ileum

Question 10

11. The major function(s) of the large intestine is (are)

Answer 10

vitamins A, D, and E.
absorption of vitamins liberated by bacterial action
storage of fecal material prior to defecation

Question 11

12. Vitamins generated by bacteria in the colon are:

Answer 11

Vitamin K, biotin, and pantothenic acid

Question 12

13. The final enzymatic steps in the digestive process are accomplished by:

Answer 12

brush border enzymes of the intestinal microvilli

Question 13

14. What are the six steps of digestion?

Answer 13

Digestion involves:

1. ingestion
2. mechanical procssing
3. secretion
4. digestion (conversion into a form usable by cells)
5. absorption
6. exretion

Question 14

15. Name and describe the layers of the digestive tract, proceeding from the innermost layer to the outermost layer.

Answer 14

Layers of the digestive tract are:

1. the mucosa: the epithelial layer that performs chemical digestion and absorption of nutrients;
2. the submucosa: the connective tissue layer containing lylmphatic and blood vessels and submucosal nerve plexus;
3. the muscularis externa: the smooth muscle layer containing the myenteric nerve plexus;
4. the serosa: the outermost layer, epithelium and connective tissue that forms the visceral peritoneum (or connective tissue that forms the adventitia).

Question 15

16. What three basic mechanisms regulate the activities of the digestive tract?

Answer 15

Activities of the digestive tract are regulated by neutral, hromonal, and local mechanisms.

Question 16

17. What are the three phases of swallowing, and how are they controlled?

Answer 16

The three phases of swallowing - the buccal, pharyngeal, and esophageal phases - are controlled by the swallowing center of the mudulla oblongata via the trigeminal and glossopharyngeal cranial nerves. The motor commands originating at the swallowing center are distributed by cranial nerves V, IX, X, and XII. Along the esophagus, primary peristaltic contractions are coordinated by afferent and efferent fibers within the glossopharyngeal and vagus cranial nerves, but secondary peristaltic contractions occur in the absence of CNS instructions.

Question 17

18. What are the primary digestive functions of the pancreas, liver and gallbladder?

Answer 17

The pancreas provides digestive enzymes, plus bicarbonate ions that elevate the pH of the chyme. The liver produces bile and is also the primary organ involved n regulating the composition of circulating blood. The gallbladder stores and releases bile, which contains additional buffers and bile salts that aid the digestion and absorption fo lipids.

Question 18

19. Which hormones produced by duodenal enteroendocrine cells effectively coordinate digestive functions?

Answer 18

The hormones include the following: enterocrinin, which stimulates the submucosal glands of the duodenum; secretin, which stimulates the pancreas and liver to increase the secretion of water and bicarbonate ions; cholecystokinin (CCK), which causes an increase in the release of pancreatic secretions and bile into the duodenum, inhibits gastric activity, and appears to have CNS effects that reduce the sensation of hunger; gastric inhibitory peptide (GIP), which stimulates insulin release at pancreatic islets and the activity of the duodenal submucosal glands; vasoactive intestinal peptide (VIP), which stimulates the secretion of intestinal glands, dilates regional capillaries, and inhibits acid production in teh stomach; gastrin, which is secreted by G cells in the duodenum when they are exposed to large quantities of incompletely digested proteins; and, in small quantities, motilin, which stimulates intestinal contractions, villikinin, which promotes the movement of villi and associated lymph flow, and somatostatin, which inhibits gastric secretion.

Question 19

20. What ar the three primary functions of the large intestine?

Answer 19

The large intestine reabsorbs water and compacts the intestinal contents into feces, absorbs important vitamins liberated by bacterial action, and stores fecal material prior to defecation.

Question 20

21. What two positive feedback loops are involved in the defecation reflex?

Answer 20

Positive fee feedback loops in the defecation reflex involve:

1. stretch receptors in the rectal walls, which promote a series of peristaltic contractions in the colon and rectum, moving feces toward the anus; and
2. the sacral parasympathetic system, also activated by the stretch receptors, which stimulates peristalsis via motor commands distributed by the pelvic nerves.

Question 21

22. During defecation,

Answer 21

• stretch receptors in the rectal wall initiate a series of peristaltic contractions in the colon and rectum.
• stretch receptors in the rectal wall activate parasympathetic centers in the sacral region of the spinal cord.

Question 22

23. Increased parasympathetic stimulation of the intestine would result in

Answer 22

none of the following:
decreased motility
decreased secretion
decreased sensitivity of local reflexes
decreased segmentation

Question 23

24. A drop in pH below 4.5 in the duodenum stimulates the secretion of

Answer 23

secretin

Question 24

25. Through which layers of a molar would an oral surgeion drill to perform a root canal (removal of the alveolar nerve in a severely damaged tooth)?

Answer 24

A root canal involves drilling through the enamel and the dentin.

Question 25

26. How is the epithelium of the stomach protected from digestion?

Answer 25

The stomach is protected from digestion by mucous secretions of its epithelial lining and by neural and hormonal control over the times and rates of acid secretion.

Question 26

27. How does each of the three phrases of gastric secretion promote and facilitate gastric control?

Answer 26

1. the cephalic phase of gistric secretion begins with the sight or thought of food. Directed by the CNS, this phase prepares the stomach to receive food.
2. the gastric phase begins with the arrival of food in the stomach; this phase is initiated by distention of the stomach, an increase in the pH of the gastric contents, and the presence of undigested materials in the stomach.
3. the intestinal phase begins when chyme starts to enter the small intestine. This phase controls the rate of gastric emptying and ensures that the secretory, digestive, and absorptive functions of the samll intestine can proceed reasonably efficiently.

Question 27

28. Nutritionists have found that after a heavy meal, the pH of blood increases slightly, especially in the veins that carry blood away from the stomach. What causes this increase in blood pH?

Answer 27

After a heavy meal, bicarbonate ions pass from the parietal cells of the stomach into the interstitial fluid. The diffusion of bicarbonate ions from the interstitial fluid. The diffusion of bicarbonate ions from the interstitial fluid into the bloodstream increases blood pH. This sudden influx of bicarbonate ions into the bloodstream has been called the “alkaline tide”.

Question 28

29. Some people with gallstones develop pancreatitis. How could this occur?

Answer 28

If a gallstone is small enough, it can pass through the common bile duct and block the pancreatic duct. Enzymes from the pancreas then cannot reach teh small intestine. As the enzymes accumulate, they irritate the duct and ultimately teh exocrine pancreas, producing pancreatitis.

Question 29

30. Harry is suffering from an obstruction in his colon. He notices that when he urinates, the color of his urine is much darker than normal, and he wonders if there is any relationship between the color of his ursine and his intestinal obstruction. What would you tell him?

Answer 29

The darker color of his urine is probably due to increased amounts of the pigment urobilin, which gives urine its normal yellow color. Urobilin is derived from urobiligen, which is formed in the large intestine by the action of intestinal bacteria on bile pigments. In an intestinal obstruction, the bile pigments cannot be eliminated by their normal route, so a larger-than-normal amount diffuses into the blood, where it is eliminated by the kidneys.

Question 30

31. A condition know as lactose intolerance is characterized by painful abdominal cramping, gas, and diarrhea. The cause of the problem is an inability to digest the milk sugar lactose. How would this cuase the observed signs and symptoms?

Answer 30

If an individual cannot digest lactose, this sugar passes into the large intestine in an undigested form. The presence of extra sugar in the chyme increases its osmolarity, so less water is reabsorbed y the intestinal mucosa. The bacteria that inhabit the large intestine can metabolize the lactose, and in the process they produce large amounts of carbon dioxide. This gas overstreches the intestine, which stimulates local reflexes that increase peristalsis. The combination of more-fluid contents and increased peristalsis causes diarrhea. The overexpansion of the intestine by gas, which is directly related to increased gas production by the bacteria, causes the sever pain and abdominal cramping.

Question 31

32. Recently, more people have turned to surgery to help them lose weight. One form of weight control surgery involves stapling a portion of the stomach shut, creating a smaller volume. How would such a surgery result in weight loss?

Answer 31

The primary effect of such surgeries would be a reduction in the volume of food (and thus in the amount of calories) consumed because the person feels full after eating a small amount. This can result in significant weight loss.