GI Flashcards
What do chief cells secrete?
Pepsin (proteolytic enzymes)
Non specifically break down proteins
What do parietal cells secrete?
HCl
Keeps luminal pH of stomach lower than 2
What do neck cells secrete?
Mucus
Basic due to amine groups on the proteins
HCO3-
Secreted into the mucus, provides a buffer for H+
What do G cells secrete?
Gastrin
What does gastrin do?
Binds to surface receptors on parietal cells, stimulating acid and intrinsic factor
Which gastric gland cells secrete HCl?
Parietal cells
Which gastric gland cells secrete pepsin?
Chief cells
Which gastric gland cells secrete gastrin?
G cells
Which gastric pit cells secrete mucus and HCO3-?
Neck cells
Which cells secrete the bile acid dependent component of bile?
Hepatocytes lining the canaliculi
What are the bile acids?
Cholic acid/ chenodeoxycholic acid
How do bile acids travel?
Conjugated to amino acids in micelles
Bile salts, cholesterol, phospholipids
Which cells secrete the bile acid independent component of bile?
Cells lining the intra-hepatic bile ducts
What is the enterohepatic circulation?
Bile acids are released from the micelles when fatty acids are absorbed in the small intestine. The bile acids continue along the small intestine to the terminal ileum, where they are absorbed by the epithelia, then flow in the hepatic portal circulation to the hepatic sinusoids. Hepatocytes take up the acids and re secrete them into canaliculi
Describe the biliary tree
Bile canaliculi ➡️ canals of Hering ➡️ intrahepatic bile ductile ➡️ interlobular bile duct ➡️ left and right hepatic ducts ➡️ common hepatic duct ➡️ common bile duct as it joins the cystic duct ➡️ ampulla of Vater as the pancreatic duct joins ➡️ duodenum
List the secretions of the exocrine pancreas
Proteases- trypsin(ogen), chymotrypsin, elastase, carboxypeptidase
Amylases
Lipases
How are pancreatic secretions stimulated?
Acinar (enzymes) - CCK and gastrin in response to hypertonicity and fats
Ductal (HCO3)- secretin in response to low pH
How are biliary secretions stimulated?
CCK released from I cells of the duodenum due to hypertonicity, peptides and fat stimulate gall bladder contractions
What would you suspect if you found eosinophils?
Parasitic infection eg worms, asthma, hay fever
Which bonds does pepsin prefer breaking?
Peptide bonds near aromatic AA side chains
Which bonds does trypsin prefer breaking?
Peptide bonds near basic AA side chains
Which bonds does chymotrypsin prefer breaking?
Bonds near aromatic AA side chains
Which bonds does carboxypeptidase prefer breaking?
C terminal AAs with basic side chains
What immunological cells are found in Ulercative Collitis?
Th2 Helper cells which produce TGF- and IL-5
What immune cells are found in Crohn’s?
Th1 helper cells which produce IFN-gamma and IL-2
Activation of Th1 cells produce the down regulatory cytokines IL-10 and TGF-
