Salivation and Gastric Function

Question 1

What are hormones?

Answer 1

Peptides released from endocrine cells of the GI tract into the portal circulation that pass through the liver before entering systemic circulation. Systemic circulation delivers to the target cell.

Question 2

What are paracrine factors?

Answer 2

Secreted by endocrine cells of the GI tract that act locally in the same tissue that secretes them.

Question 3

3 main paracrine control factors

Answer 3

1. Serotonin- produced by enterochromaffic cells in intestine in response to distension. Indirectly excites ENS to increase motility and secretions.
2. Somatostatin- produced by D cells and is an inhibitor of secretions and motility. Can act in endocrine or paracrine manner.
3. Histamine- released by EC-like cells in the stomach and potently stimulate HCl secretion

Question 4

What are neurocrines?

Answer 4

Synthesized in neurons in the GI tract and are released following an action potential.

Ex: ACh, Norepi, VIP, gastrin-releasing peptide, substance P

Question 5

Gastrin

Answer 5

Secreted by antral mucosa cells (G cells in stomach) in response to food, distension, vagus. Increases acid secretion by parietal cells and stimulates gastric mucosa growth.

Question 6

Cholecystokinin (CCK)

Answer 6

Secreted by mucosa of intestine (I cells in duodenum and jejunum) in response to fats and proteins/peptide/aminoacids. Increases gall bladder contraction and pancreatic enzyme and bicarbonate secretion. Inhibits gastric emptying.

Question 7

Secretin

Answer 7

Secreted by mucosa of intestine (S-cells in duodenum) in response to acidic chyme. Increases bicarbonate and fluid secretion by the pancreas. Decreases gastric acid secretion in stomach by decreasing gastrin. Inhibits gastric emptying.

Question 8

Motilin

Answer 8

Secreted by mucosa of small intestine (M cells in duodenum and jejunum) during fasting. Promotes contractions in distal stomach and intestines to clear the tract.

Question 9

Glucose-dependent insulinomic peptide (GIP)

Answer 9

Secreted by mucosa of small intestine (K cells in duodenum and jejunum) in response to fat and carbs. Acts on pancreas to stimulate insulin secretion. Inhibits HCl secretion by parietal cells.

Question 10

Salivary digestive enzymes

Answer 10

• Amylase: starch digestion

- Lingual lipase: lipid digestion

Question 11

Gastric digestive enzymes

Answer 11

-Pepsin: protein digestion

Question 12

Intestinal digestive enzymes

Answer 12

• Enterokinases, disaccharidases, peptidases

- Amylase, Trypsin, Lipase, Chemotrypsin–carb, protein, lipid digestion

Question 13

Oxynic glands

Answer 13

• Acid forming glands in stomach
• 3 cell types: mucous neck cells, peptic (chief cells)–pepsinogen and gastric lipase, parietal cells–hydrochloric acid and intrinsic factor

Question 14

Pyloric glads

Answer 14

• Mucus secreting glands in the stomach
• Secrete gastrin (G cells)
• Secrete somatostatin (D cells)

Question 15

Stimulators of acid secretion

Answer 15

-Histamine, vagus (ACh), gastrin

Question 16

Inhibitors of acid secretion

Answer 16

-Somatostatin, GIP, Secretin