Gastric and Intestinal Secretions

Mucus

Protective barrier

Hydrochloric Acid (HCl)

Dissolve food fibers, bactericide, converts pepsinogen to pepsin

Pepsinogen/Pepsin

breaks down protein forming polypeptides

Gastrin

Stimulates gastric glands to secrete HCl, pepsinogen, and histamine

Intrinsic Factor (mucoprotein)

Intestinal absorption of vitamin B12

Gastroferrin (glycoprotein)

facilitates small intestinal absorption of iron

somatostatin

Inhibits acid, pepsinogen, and histamine secretion and release of gastrin

Histamine

Stimulates acid secretion

Acetylcholine

Stimulates release of pepsinogen and acid secretion

Gastrin-releasing peptide

stimulates gastrin and release of pepsinogen and acid secretion

Ghrelin

Stimulates growth hormone secretion and hypothalamus to increase appetite

motilin

increases GI motility

Secretin

Stimulates the pancreas and liver, decreased GI motility, inhibits gastrin and acid secretion

serotonin

stimulates intestinal secretion, motility and sensation, vasodilation, activates gut immune response

Cholecystokinin (CCK)

stimulates gallbladder and pancreas, decreases motility, constricts pyloric sphincter, inhibits gastrin

Enteroglucagon

Inhibits gastric and pancreatic secretion, enhances insulin release/lipolysis/ketogenesis/glycogenolysis

Gastric inhibitory peptide

Inhibits gastric secretion and emptying, stimulates insulin release

Peptide YY

Inhibits postprandial gastric acid and pancreatic secretion, delays gastric and small bowel emptying

Pancreatic polypeptide

decreases pancreatic HCO3 and enzyme secretion

Vasoactive intestinal peptide

Relaxes intestinal smooth muscle