HNSC 3310 GI secretions (Lumen of Small Intestine)

Cholecystokinin (CCK; chole=bile, cysti=bladder, kinin=to move)

Secretion is stimulated by presence of fat and protein in small intestine Stimulates biliary and pancreatic secretions by causing relaxation of the Sphincter of Oddi and contraction of gall bladder

Bicarbonate

Neutralizes gastric contents (pH 1-2 → pH 7-8)

Pancreatic amylase

Cleaves α-1,4 bonds of starch producing a mixture of linear oligosaccharides, branched α-limit dextrins, maltotriose and maltose

Enterokinase

Presence of chyme in duodenum stimulates its release Activates trypsinogen —-) trypsin

Trypsin

Activates other pancreatic proteases (chymotrypsin, carboxypeptidase)

Chymotrypsin, Carboxypeptidase

Produce smaller polypeptides as they cleave proteins between specific amino acids

Elastase

Digests fibrous protein

Bile

Released from gall bladder Emulsifies fat

Pancreatic lipase

TG —-) 2 FAs + 2-monoglyceride (cleaves FAs at sn-1 and sn-3 positions)

Phospholipase A2

Phospholipid ——) FA + lysophospholipid (cleaves FA at sn-2 position)

Enterogastrone

Stimulated by undigested lipid in the stomach & slows gastric emptying (contributes to satiety of dietary fats)

Pancreatic deoxyribonuclease

DNA ——) mononucleotides

Pancreatic ribonuclease

RNA —-) mononucleotides