GI Physiology lecture 2 Flashcards
Name 2 drugs affected by the stomach (acid)
penicillin, erythromycin
what properties do drugs need to be absorbed in the stomach?
- lipid soluble
- weakly acidic
Describe what a gastric sleeve is
stomach cut and stapled, 70-80% excised
describe a gastric band
reduces food intake at any one time
describe a Roux en Y bypass
gastric bypass with small pouch. Gastric balloon. Similar to band but inflated in stomach
Name 3 surgical obesity treatments
- gastric sleeve
- gastric band
- roux en y bypass
why is mucous secreted in the stomach? (mucous layer)
alkaline neutralises HCl acid
Mucous presents pepsin penetrating to stomach epithelia
Describe tight junctions in the stomach
Protein complexes keeping cells together. They restrict movement of acid/protease to underlying stomach epithelia
How are the stomach cells adapted to their harsh environment?
There is a high cell turnover. Damaged cells are renewed every 2-3 days from the gastric pits.
What happens if there is a breakdown of barrier layer? i.e. mucous layer in the stomach?
cells are exposed to HCl and protease, this leads to a gastric/duodenal ulcer
This can extend deep into GI wall, damaging blood vessels and haemoorhaging
Severe complete evasion through wall causes a perforated ulcer. This causes the escape of food secretions and bacteria into the peritoneal cavity.
This can lead to peritonitis, then severe shock and death
What is a likely organism responsible for GIT infections?
Helicobacter pylori
It infects the gastric mucosa. This causes reduced barrier efficiency of the mucosa and leads to ulceration
treatment of Helicobacter pylori
2 antibiotics + PPI
Dirithromycin + amoxicillin + omeprazole
OR
Clarithromycin + amoxicillin/metronidazole + omeprazole
pH equation
pH = pKa + log([A-]/{HA])
what is peristalsis
a wave of muscular contraction
how does food travel down the GIT?
Describe the forces that make this happen
Food bolus/chyme goes through duodenum
Circular muscles contract, preventing backflow of chyme
Longitudinal muscles contract further along to move food along
describe diarrhoea in terms of muscles
Peristalsis of longitudinal muscle
Excessive ion and fluid loss
Anti-diarrhoea medicine and how it works
Loperamide
Acts on MP, targets um opioid receptors in the MP. Reduces muscle tone so controls (liquids) stay in the intestine longer, so more absorption of fluid
less diarrhoea
Role of bile acids
Where are they stored?
Bile acids responsible for liquid emulsification which is important in absorbing lipids e.g. vitamins ADEK
Bile acids stored in the gall bladder
One cause of atherosclerosis
high cholesterol
How do statins work?
Statins block the enzyme HMG-CoA reductase, hence reducing cholesterol
Layers of the colon from outside to in
Serosa Longitudinal muscle MP (Myenteric Plexus) Circular muscle Epithelium Lumen
How are bile acids made?
Acetyl CoA→HMG CoA→Mevalonate→Cholesterol→Bile acids
Where are bile acids made?
Liver
How do bile acids travel out of the liver?
Bile acids go through the intestinal veins→then the superior mesenteric vein→then the hepatic portal vein and then the iluem
Hormone that causes bile to leave gallbladder
Cholecystokinin (CKK)
causes gall bladder to contract
bile released
Describe the path of bile travel from the liver to the duodenum
THEN
path of travel from liver to gall bladder
Liver→common hepatic duct→common bile duct→duodenum
Liver→common hepatic duct→cystic duct→gall bladder
