GIT Physiology AB Flashcards
Gastrin - which cells secrete this and where are the cells located?
G cells in the antrum of the stomach
Gastrin - what stimulates secretion?
Food
High antral pH
Vagus nerve
Luminal peptides/amino acids
Gastrin - what inhibits secretion?
Low antral pH
Somatostatin
Gastrin - which cells does it target?
Parietal cells (H+) D cells (somatostatin)
Gastrin - what are the 3 major functions?
- Increase HCL, pepsinogen and IF secretion
- Increases gastric motility
- Stimulates parietal cell maturation
Cholecystokinine - which cells secrete this?
I cells in the proximal small bowel
Cholecystokinine - what stimulates secretion?
Partially digested proteins and triglycerides
Cholecystokinine - what are the 5 major functions?
- Increased pancreatic enzyme secretion
- Contraction of gallbladder
- Relaxation of sphincter of oddi
- Decreased gastric emptying
- Induces satiety
Somatostatin - which cells secrete this?
D cells in the stomach and pancreas
Somatostatin - what stimulates secretion?
Fat, bile salts and glucose in the intestinal lumen
Somatostatin - what are the major functions?
- Decreases acid and pepsin secretion
- Decreases gastrin secretion
- Decreases pancreatic enzyme secretion
- Decreases insulin and glucagon secretion
- Inhibits trophic effects of gastrin
- Stimulates gastric mucous production
Secretin - which cells secrete this?
S cells in the upper small bowel
Secretin - what stimulates secretion?
Acidic chyme, fatty acids
Secretin - what are the 3 major function?
- Increases secretion of bicarbonate-rich fluid from pancreas and hepatic duct cells
- Decreases gastric acid secretion
- Trophic effect on pancreatic acinar cells
Vasoactive intestinal peptide - where is this secreted from?
Myenteric inhibitory motor neurons/submucosal neurons
Vasoactive intestinal peptide - what stimulates secretion?
Neural stimulation
Vasoactive intestinal peptide - what is the function?
- Stimulates secretion by pancreas and intestines
2. Inhibits acid secretion
Parietal cell - where is it located?
Body and fundus of stomach
Parietal cell - what stimulates this cell and via which receptor?
Histamine - H2 receptor
Gastrin - CCK-B receptor
ACh - M3 receptor via vagus nerve
Parietal cell - what does it secrete?
HCL
Intrinsic factor
What are the causes of hypergastrinaemia?
Prolonged acid inhibition with PPI/H2RA - commonest
Atrophic gastritis - pernicious anaemia, H pylori
Vagotomy/SB resection
Rare: ZE syndrome, renal failure, hypercalcaemia
Artefactual: hyperlipidaemia
The action of the brush border enzyme maltase results in the formation of what?
maltase: cleaves disaccharide maltose to glucose + glucose
The action of the brush border enzyme sucrase results in the formation of what?
sucrase: cleaves sucrose to fructose and glucose
The action of the brush border enzyme lactase results in the formation of what?
lactase: cleaves disaccharide lactose to glucose + galactose
