Lecture 5 Test 3

The major function(s) of the large intestine is (are) a. reabsorption of water and compaction of feces b. absorption of vitamins liberated by bacterial action c. storage of fecal material prior to defecation d. a, b, and c

D

Name the three regions of the small intestine from proximal to distal.

the three regions of the small intestine are the duodenum, jejunum, and ileum.

Vitamins generated by bacteria in the colon are a. vitamins A, D, and E b. B complex vitamins and vitamin C c. Vitamin K, biotin, and pantothenic acid d. niacin, thiamine, and riboflavin.

C

Identify the four regions of the colon.

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

How would the pH of the intestinal contents be affected if the small intestine did not produce secretin?

The hormone secretin, among other things, stimulates the pancreas to release fluid high in buffers to neutralize the chime that enters the duodenum from the stomach. If the small intestine did not secrete secretin, the pH of the intestinal contents would be lower that normal.

What are some major histological differences between the large intestine and the small intestine?

The large intestine is larger in diameter than the small intestine, but its thin wall lacks villi and has an abundance of mucous cells and intestinal glands.

A branch of the portal vein, hepatic artery, and tributary of the bile duct form a. a live lobule b. the sinusoids c. a portal area d. the hepatic duct e. the pancreatic duct

C

A drop in the pH below 4.5 in the duodenum stimulates the secretion of a. secretin b. cholecystokinin c. gastrin d. a, b, and c

A

Bile release from the gallbladder into the duodenum occurs only un the stimulation of a. cholecystokinin b. secretin c. gastrin d. enteropeptidase

A

Regional movements that occur in the small intestine and function to churn and fragment the digestive material are called. a. segmentation b. pendular movements c. peristalsis d. mass movements e. mastication

A

The final enzymatic steps in the digestive process are accomplished by a. brush border enzymes of the intestinal microvilli b. enzymes secreted by the stomach c. enzymes secreted by the pancreas d. the action of bile from the gallbladder

A

Does a high-fat meal raise or lower the level of cholecystokinin in the blood?

A high fat meal would raise the cholecystokinin level in the blood.

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

Positive 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.

The digestion of which nutrient would be most impaired by damage to the exocrine pancreas?

Damage to the exocrine pancreas would most impair the digestion of fats (lipids), because it is the primary source of lipases. Even though such damage would also reduce carbohydrate and protein digestion, enzymes for digesting these nutrients are produced by other digestive system structures, including the salivary glands (carbohydrates) the small intestine (carbohydrates and proteins) and the stomach (proteins)

During defecation a. stretch receptors in the rectal wall initiate a series of peristaltic contraction in the colon and rectum b. stretch receptors in the rectal wall activate parasympathetic centers in the sacral region of the spinal cord c. the internal anal sphincter relaxes while the external anal sphincter contracts. d. all of these occur e. only a and b occur

E

Increase parasympathetic stimulation of the intestine would result in a. decrease motility b. decreased secretion c. decrease sensitivity of local reflexes d. decrease segmentation e. none of these

E

Differentiate between haustral churning and mass movements.

In mass movements, which occur a few times per day throughout the transverse colon and the distal portions of the large intestine, strong peristaltic contractions move material along the length of the colon. In haustral churning, segmentation movements mix the contents of nearby haustral.

What are the three primary functions of the large intestine?

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.

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

The hormones include the following: enteroccrinin 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 the 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.

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

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 in 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 of lipids.

How is the small intestine adapted for the absorption of nutrients?

the small intestine has several adaptations that increase its surface area and thus its absorptive capacity. The walls of the small intestine have folds called the plicae circulares. The tissue that covers the plicae circulares forms fingerlike projections, the villi. THe epithelial cells that cover the villi have an exposed surface covered by small fingerlike projections the microvilli. In addition the small intestine has a very rich supply of blood vessels and lymphatic vessels, which transport the nutrients that are absorbed.