The Digestive System - Chapter 24

Question 1

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

Answer 1

chemical digestion

Question 2

The outer layer of the digestive tract is known as the:

Answer 2

serosa

Question 3

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

Answer 3

mesenteries

Question 4

A branch of the hepatic portal vein, hepatic artery proper, and branch of the bile duct form the:

Answer 4

a portal area

Question 5

Most of the digestive tract is lined by _______ epithelium.

Answer 5

simple columnar

Question 6

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

Answer 6

segmentation

Question 7

Bile release from the gallbladder into the duodenim occurs only under the stimulation of:

Answer 7

cholecystokinin

Question 8

The major functions of the large intestine are:

Answer 8

reabsorption of water and compaction of feces, absorption of vitamins liberated by bacterial action, and storage of fecal material prior to defecation.

Question 9

vitamins generated by bacteria in the colon are

Answer 9

Vitamin K, Biotin, and Pantothenic Acid

Question 10

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

Answer 10

brush border enzymes of the intestinal microvilli

Question 11

What are the six main functions of the digestive system?

Answer 11

1. Ingestion
2. Mechanical Processing
3. Secretion
4. Digestion (conversion into a form digestible by cells)
5. Absorption
6. Excretion

Question 12

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

Answer 12

1. Mucosa (innermost)
2. Submucosa
3. Muscularis
4. Serosa

Question 13

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

Answer 13

Local, Hormonal, and Neural Mechanisms

Question 14

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

Answer 14

1. Buccal
2. Pharyngeal
3. Esophageal

Question 15

What are the primary digestive functions of the pancreas?

Answer 15

provides digestive enzymes and bicarbonate ions that elevate the pH of the chyme.

Question 16

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

Answer 16

Enterocrinin, Secretin, Cholecystokinin, Gastric Inhibitory Peptide (GIP), Vasoactive Intestinal Peptide (VIP), Gastrin, Motilin, Villikinin, somatostatin

Question 17

What are the three primary functions of the large intestine?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

22. During defecation,

Answer 19

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

Question 20

Increased parasympathetic stimulation of the intestine would NOT result in:

Answer 20

decreased motility, decrease secretion, decreased sensitivity of local reflexes, decreased segmentation.

Question 21

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

Answer 21

secretin

Question 22

Through which layers of a molar would an oral surgeon drill to perform a root canal?

Answer 22

drilling through the ENAMEL and DENTIN

Question 23

How is the epithelium of the stomach protected from digestion?

Answer 23

mucous secretions of it’s epithelial lining and by neural and hormonal control over the times and rates of acid secretion.

Question 24

How does each of the three phases of gastric secretion promote and facilitate gastric control?

Answer 24

1. Cephalic Phase - Begins with the sight or thought of food. Directed by the CNS, this phase prepares the stomach to receive food.
2. Gastric Phase - Begins with the arrival of food in the stomach, initiated by distension of the stomach, an increase in the pH of the gastric contents, and the presence of undigested materials in the stomach.
3. Intestinal Phase - Begins when chyme starts to enter the small intestine. Controls the rate of gastric emptying and ensures that the secretory digestive, and absorptive functions of the small intestine can proceeded reasonable efficiently.

Question 25

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 25

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 into the bloodstream increases blood pH. This sudden influx of bicarbonate ions into the bloodstream has been called the alkaline tide.

Question 26

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

Answer 26

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

Question 27

Harry is suffering from an obstruction of 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 urine and his intestinal obstruction. What would you tell him?

Answer 27

Likely due to the increase amounts of pigment UROBILIN, which gives urine it’s normal yellow color. Urobilin is derived from urobilinogen, 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 bloodstream, where the kidneys eliminate it.

Question 28

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

Answer 28

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

Question 29

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 29

Reduction of the volume of food (an thus calories) consumed because the person feels full after eating a small amount.

Question 30

What is the function of Vasoactive intestinal Peptide?

Answer 30

VIP stimulates the secretion of intestinal glands, dilates regional capillaries, and inhibits acid producation in the stomach.

Question 31

What is the function of Gastrin?

Answer 31

secreted by G cells in the duodenum when they are exposed to large quantities of incompletely digested proteins

Question 32

What is the function of Motilin?

Answer 32

stimulates intestinal contractions

Question 33

What is the function of Villikinin?

Answer 33

Promotes the movement of villi and associated lymph flow

Question 34

What is the function of Somtostatin?

Answer 34

inhibits gastric secretion