Chapter 24 - the digestive system - REVIEW

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 organs of the peritoneal cavity are the…..

Answer 3

mesenteries

Question 4

a branch of the portal vein, hepatic artery, and tributary of the bile duct form a….

Answer 4

portal area

Question 5

most of the digestive tract is lined by what kind of 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 released from the gallbladder into the duodenum ONLY OCCURS under the stimulation of…..

Answer 7

cholecystokinin

Question 8

name 3 major functions of the large intestine

Answer 8

reabsorption of water and compaction of feces

absorption of vitamins liberated by bacterial action

storage of fecal material prior to defecation

Question 9

name the 3 vitamins generated by bacteria in the colon

Answer 9

vitamin k
biotin
vitamin b5 (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 6 steps of digestion

Answer 11

-ingestion
-mechanical processing
-digestion
-secretion
-absorption
-excretion

Question 12

name and describe the layers of the digestive tract, proceeding from the innermost layer to the outermost layer

Answer 12

mucosa
submucosa
muscularis externalis
serosa

mucosa - epithelial layer that performs chemical digestion and absorption of nutrients

submucosa - connective tissue layer containing lymphatic and blood vessels and the submucosal nerve plexus

muscularis externa - smooth muscle layer containing the myentric nerve plexus

serosa - epithelium and connective tissue that forms the visceral peritoneum (or connective tissue that forms the adventitia)

Question 13

what 3 basic mechanisms regulate the activities of the digestive tract?

Answer 13

-local
-neural
-hormonal

Question 14

What are the 3 phases of swallowing, and how are they controlled?

Answer 14

buccal phase
pharyngeal phase
esophageal phase

all controlled by the swallowing center of the medulla oblongata

Question 15

what are the primary digestive functions of the pancreas, liver, and gallbladder

Answer 15

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

liver - produces bile and is the primary organ responsible for regulating the composition of circulating blood

gallbladder - stores and releases bile, which contains additional buffers and bile salts

Question 15

what are the primary digestive functions of the pancreas, liver, and gallbladder

Answer 15

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

liver - produces bile and is the primary organ responsible for regulating the composition of circulating blood

gallbladder - stores and releases bile, which contains additional buffers and bile salts that aid in digestion and absorption of lipids

Question 16

what 2 positive feedback loops are involved in the defecation reflex

Answer 16

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

Question 17

during defecation….. which relaxes and contracts between the internal anal sphincter and external anal sphincter

Answer 17

contracts - internal
relaxes - external

Question 18

a drop in pH below 4.5 in the duodenum stimulates the secretion of…..

Answer 18

secretin

Question 19

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

Answer 19

through the enamel and dentin

Question 20

how is the epithelium of the stomach protected by digestion?

Answer 20

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

Question 21

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

Answer 21

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 and into the bloodstream increases blood pH. This sudden influx of bicarbonate ions is called the “alkaline tide”

Question 22

what are the 3 phases of gastric secretion

Answer 22

1. cephalic phase
2. Gastric phase
3. Intestinal phase

Question 23

When does each phase of gastric secretion begin?

Answer 23

cephalic phase begins with the sight or thought of food

gastric phase begins with the arrival of food in the stomach

intestinal phase begins when chyme starts to enter the small intestine

Question 24

explain the cephalic phase of gastric secretion

Answer 24

-directed by the central nervous system
-way of preparing the stomach to receive food

Question 25

explain the gastric phase of gastric secretion

Answer 25

-phase is initiated by distension of the stomach , an increase in the pH of the gastric contents, and the presence of undigested materials in the stomach

Question 26

explain the intestinal phase of gastric secretion

Answer 26

-controls the rate of gastric emptying and ensures that secretory, digestive, and absorptive functions of the small intestine can proceed efficiently