Gastrointestinal Physiology

Question 1

Understand and be able to describe the basic mechanisms by which different digestive organs contribute to the breakdown of complex foodstuffs into small molecules that can be absorbed into blood.

Answer 1

• Chewing/mechanical: mouth tongue
• Deglutition: pharynx and esophagus
• Digestion: stomach and small intestine
• Absorption: small intestine, large intestine

Question 2

Understand the physiology of gastrointestinal smooth muscle and patterns of gastrointestinal motility.

Answer 2

Under local neurological and hormonal control. The GIT undergoes slow waves and “action potentials” are spike potentials.

Question 3

Describe the basic anatomy of the enteric nervous and endocrine systems and how they coordinate digestive processes.

Answer 3

Intrinsic control comes from the enteric nervous system which is located in the GIT wall from esophagus to anus. It controls the myenteric and submucosal plexus.

Extrinsic control is from the autonomic nervous system (PNS, Ach stimulation. SNS, E/NE inhibition)

Question 4

GI Peptide hormones

Answer 4

Gastrin: Released by antral G cells in the duodenum. Stimulated by protein/ inhibited by acidification. Action is to stimulate HCl release from parietal cells and mucosa in stomach, duodenum and colon.
CCK: I-cells in duodenum, jejunum and ileum. Stimulated by amino acids, fatty acids, monoglycerides. Action to stimulate gall bladder to release bile into SI, inhibits gastric emptying, appetite suppressant.
Secretin: S cells of the duodenum. stimulated by acids or fatty acids in duodenum. Action, nature’s “antiacid”. Stimulates pepsin secretion, biliary and pancreatic bicarbonate secretion, and growth of exocrine pancreas. inhibits gastric acid secretion.
GLIP: K cells of duodenum and proximal jejunum in response to protein, fat and carbs. Action to decrease gastric motility, stimulates insulin release, and inhibits gastric acid secretion.
Motilin: Released from M-cells of duodenum and proximal jejunum. Aciton stimulates upper GI motility, responsible for housekeeping contractions.

Lecture 54, Slide 43

Question 5

Gastrin

Answer 5

Gastrin: Released by antral G cells in the duodenum. Stimulated by protein/ inhibited by acidification. Action is to stimulate HCl release from parietal cells and mucosa in stomach, duodenum and colon.

Question 6

CCK

Answer 6

CCK: I-cells in duodenum, jejunum and ileum. Stimulated by amino acids, fatty acids, monoglycerides. Action to stimulate gall bladder to release bile into SI, inhibits gastric emptying, appetite suppressant.

Question 7

Secretin

Answer 7

Secretin: S cells of the duodenum. stimulated by acids or fatty acids in duodenum. Action, nature’s “antiacid”. Stimulates pepsin secretion, biliary and pancreatic bicarbonate secretion, and growth of exocrine pancreas. inhibits gastric acid secretion.

Question 8

GLIP

Answer 8

GLIP: K cells of duodenum and proximal jejunum in response to protein, fat and carbs. Action to decrease gastric motility, stimulates insulin release, and inhibits gastric acid secretion.

Question 9

Motilin

Answer 9

Motilin: Released from M-cells of duodenum and proximal jejunum. Aciton stimulates upper GI motility, responsible for housekeeping contractions.