Physiology of the Stomach 2

Transport of food & digestion in the stomach

Muscularis enables food to be churned, whole proteins are chewed and swallowed into the stomach, HCl denatures proteins, unfolding their structure to reveal the polypeptide chain, enzymatic digestion by pepsin forms shorter polypeptides which leads on to further digestion in the small intestine

Proteins are broken down by ______, only active in ____ environment, converted from pepsinogen by ___

pepsin, acid, HCl

How is gastric emptying regulated?

Emptying is inhibited by the distension of the duodenum, presence of fat or increased [HCl] known as enterogastric reflex, prevents too uch chyme entering duodenum all at once and aids digestion, this has implications for drug absorption

What do gastric contractions depend on?

neuronal and hormonal input to the antrum smooth muscle

Effect of fat content on gastric emptying

fat in duodenum causes fundus to relax, lowering intragastric pressure, high fat increases feeling of fullness for longer and prolongs the elevation of pH in the stomach

Control of stomach expansion

parietal cells, proton pump & ions produce gastric acid, this is controlled by Ach, gastrin, histamine increase and somatostatin decrease. Alkaline mucous stops gastric acid from destroying the stomach

Gastric Ulcers

Caused by erosion of mucosal layer, leading to inflammation and damage to underlying tissue, linked to stress and excess acid, can be brought on by remaining ulcers to to NSAID use, smoking, alcohol