Chapter 24 - the digestive system - REVIEW Flashcards
the enzymatic breakdown of large molecules into their basic building blocks is called…..
chemical digestion
the outer layer of the digestive tract is known as the……
serosa
double sheets of peritoneum that provide support and stability for organs of the peritoneal cavity are the…..
mesenteries
a branch of the portal vein, hepatic artery, and tributary of the bile duct form a….
portal area
most of the digestive tract is lined by what kind of epithelium?
simple columnar
regional movements that occur in the small intestine and function to churn and fragment the digestive material are called…..
segmentation
bile released from the gallbladder into the duodenum ONLY OCCURS under the stimulation of…..
cholecystokinin
name 3 major functions of the large intestine
reabsorption of water and compaction of feces
absorption of vitamins liberated by bacterial action
storage of fecal material prior to defecation
name the 3 vitamins generated by bacteria in the colon
vitamin k
biotin
vitamin b5 (pantothenic acid)
the final enzymatic steps in the digestive process are accomplished by….
brush border enzymes of the intestinal microvilli
what are the 6 steps of digestion
-ingestion
-mechanical processing
-digestion
-secretion
-absorption
-excretion
name and describe the layers of the digestive tract, proceeding from the innermost layer to the outermost layer
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)
what 3 basic mechanisms regulate the activities of the digestive tract?
-local
-neural
-hormonal
What are the 3 phases of swallowing, and how are they controlled?
buccal phase
pharyngeal phase
esophageal phase
all controlled by the swallowing center of the medulla oblongata
what are the primary digestive functions of the pancreas, liver, and gallbladder
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
what are the primary digestive functions of the pancreas, liver, and gallbladder
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
what 2 positive feedback loops are involved in the defecation reflex
- stretch receptors in the rectal walls promote a series of peristaltic contractions in the colon and rectum, moving feces towards the anus
- the sacral parasympathetic system (also activated by the stretch receptors) stimulates peristalsis via motor commands distributed by the pelvic nerves
during defecation….. which relaxes and contracts between the internal anal sphincter and external anal sphincter
contracts - internal
relaxes - external
a drop in pH below 4.5 in the duodenum stimulates the secretion of…..
secretin
through which layers of a molar would an oral surgeon drill to perform a root canal?
through the enamel and dentin
how is the epithelium of the stomach protected by digestion?
by mucous secretions of the epithelial lining and by neural and hormonal control over the times and rates of acid secretion
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?
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”
what are the 3 phases of gastric secretion
- cephalic phase
- Gastric phase
- Intestinal phase
When does each phase of gastric secretion begin?
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
explain the cephalic phase of gastric secretion
-directed by the central nervous system
-way of preparing the stomach to receive food
explain the gastric phase of gastric secretion
-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
explain the intestinal phase of gastric secretion
-controls the rate of gastric emptying and ensures that secretory, digestive, and absorptive functions of the small intestine can proceed efficiently
