Lecture 14 - Physiology of the stomach Flashcards
What are sphincters?
open and close to allow food to travel through GI
What does pepsin do?
hydrolyses proteins into polypeptides and amino acids which stimulate acid production.
How much absorption occurs in the stomach?
very limited amount
how is contraction of layers of muscle in stomach controlled?
via myenteric plexus receiving input from ANS
at what pH is pepsin inactivated?
above pH 6
Stomach emptying involves:
-constriction of lower oesophageal sphincter
-contraction of gastric muscularis
-relaxation of pyloric sphincter
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How is gastric emptying inhibited?
by the distension of the duodenum, presence of fat or increased HCL conc. Known as enterogastric reflex.
Why does gastric emptying need to be inhibited?
to prevent too much chyme entering duodenum, and aids better digestion/absorption.
What’s the effect of fat in the duodenum?
Delays gastric emptying. Causes fundus to relax, lowering intragastric pressure. Prolonged elevation of pH in stomach.
What things influence gastric emptying?
composition of food, posture, volume, temp, pregnancy, (migraine, gastric ulcer, pernicious anaemia)
What is absorbed in the stomach?
water, electrolytes, alcohol and some drugs. Stomach wall impermeable to most materials. Absorption starts properly in small intestine.
What is an ulcer?
the erosion of mucosal layer, leading to inflammation and damage to underlying tissue. Acid not necessarily the initial damaging feature.
Main causes of gastric ulcers
Vast majority due to H pylori infection. Rest are due to NSAID use. Factors such as smoking, caffeine, alcohol and stress may contribute
Management of gastric ulceration
explanation and reassurance, dietary control, drug therapy (control of acid production), antibiotics (to get rid of H.Pylori)
