GI Flashcards
What does VIP do
inhibits acid secretion by stimulating somastatin production, released by the pancreas and SI
What are the foregut structures? and blood supply?
Mouth to proximal part of duodenum. Coeliac trunk
What is a midgut structure? and bloody supply?
Distal half of duodenum to splenic flexure of the colon. superior mesenteric artery
What is a hindgut structure and what is its blood supply?
Descending colon to the rectum. inferior mesenteric artery
Describe the coeliac trunk
major artery that supplies the foregut of the GI system, arises from the abdo aorta at 12th verterbrae, gives three branches: left gastric, common hepatoc and splenic arteries
What is the trachea lined with?
Stratified squamous cells
What is the stomach lined with?
Simple columnar epithelium with gastric glands: oxytinc (parietal = HCL and chief= pepsinogen) and pyloric glands. G cells=gastrin creates more HCL
What does enterokinase do?
Breakdown trypsinogen to trypsin
What do all peptide hormones act on?
G-protein coupled receptors
What does the pancreas secrete?
Islets of langerhans (endocrine)- hormone producing cells
Exocrine- digestive enzymes
Alkaline fluid from duct cells to neutralise acidic chyme
What do all dietary carbohydrates change into for absorption?
Monosaccharides
Phases of gastric acid secretion?
- cephalic- in head
- gastric- stomach
- intestinal- after food leaves stomach
What are the gastric secretions?
In fundus and body: HCL -> pepsinogen -> pepsin Intrinsic factor + gastroferrin -> binds b12 and Fe facilitating subsequent absorption Histamine -> HCL secretion Mucus -> protective
In pyloric gland:
Gastrin -> HCL secretion and motility
Somatostatin -> inhibits HCL secretion
What is the primary NA absorption mechanism in the interdigestive period?
Na/H and Cl/HCO3 exchange in parallel in ileum and proximal colon, regulated by cAMP. cGMP and Ca2 reduce NaCl absorption by affecting CFTR channel
What regulates Na absorption in distal colon?
Enac channels increased by aldesterone
What are the cellular mechanisms of Cl absorption?
Passively via transcellular routes
Small intestine: -ve potential due to Na transport
Large intestine: through enac
Ileum, proximal and distal colon = Cl - HCO3 exchange
Ileum+ proximal colon= NaH and ClHCO3 exchange
How is secretory diarrhoea produced?
Secretions from CFTR from bacterial enterotoxin hormones, neurotransmitters and immune cell products and laxatives => open channels at apical membrane and insertion of channels from extracellular vesicles to membrane
What is Hesselbach’s triangle and its boundaries.
Discuss the difference between a direct or inguinal hernia through this
The inguinal triangle:
Inferior: inguinal ligament
Medial: lateral border of inferior epigastric vessels
Lateral: inferior epigastric vessels
A direct hernia would pass medial to the inferior epigastric vessels through the inguinal triangle and enters the inguinal canal, it then exits the the canal via the superficial ring
An indirect hernia would pass lateral to the inferior epigastric vessels and enter the inguinal canal via the deep inguinal ring
Describe somatostatin
Secreted by D cells in stomach and pancreas. 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
Describe secretin
S cells in upper small intestine. Increases secretion of bicarbonate-rich fluid from pancreas and hepatic duct cells, decreases gastric acid secretion, trophic effect on pancreatic acinar cells
Describe CCK
Secreted from I cells in upper stomach. Increases secretion of enzyme-rich fluid from pancreas, contraction of gallbladder and relaxation of sphincter of Oddi, decreases gastric emptying, trophic effect on pancreatic acinar cells, induces satiety
What factors increase gastric acid secretion?
Vagal nerve stimulation
Gastrin release
Histamine release (indirectly following gastrin release) from enterchromaffin like cells
What factors decrease gastric acid secretion
Somatostatin (inhibits histamine release)
Cholecystokinin
Secretin
Where is the most iron absorbed
Duodenum
Name the boundaries of the inguinal canal
Anterior wall – aponeurosis of the external oblique, reinforced by the internal oblique muscle laterally.
Posterior wall – transversalis fascia.
Roof – transversalis fascia, internal oblique, and transversus abdominis.
Floor – inguinal ligament (a ‘rolled up’ portion of the external oblique aponeurosis), thickened medially by the lacunar ligament.
