GI Secretions Flashcards
(18 cards)
Where is cholecystikinin released?
From the I cells in the upper small intestine
What stimulates release of CCK, what is its receptor
Fatty acids and peptides entering the SI lumen
CCK-A receptors
What are the two main effects of CCK
Stimulation of pancreatic acidaemia secretion
Stimulation if gall bladder opening
How long is CCK
33 amino acids - last 5 are identical to Gastrin
Where is secretin released from
S cells of the small intestine
What is secretin synthesised as then converted to the active form
Preprosecretin - 121 aa
Then processed to form active secretin 27 aa
Where are the S cells found
The crypts of leiberkhun in small intestinal crypts
AND
Surface epithelium
Mainly in duodenum then decreases in Jejeny=um
Lesser so:
- pancreas
- biliary system
What type of receptor is the secretin receptor
G protein coupled which produces cAMP in the target cells
What stimulates secretin secretion?
Acid in the SI
What is the main effects of secretin?
- bicarbonate secretion from liver and pancreas
- smaller effect on enzyme secretion from the pancreatic ducts and acinar cells
- increases bile and gastric pepsin secretion
- reduces gastric acid secrection, Gastrin secretion
- increases insulin after meal
- acts on brown adipose to decrease appetite
- increases oesophageal sphincter to be
what are the pancreatic proteases
- trypsinogen
- chymotrypsinogen
- proelastase
- procarboxypeptidases A and B
- trypsin inhibitors
What activates chymotrypsin from trypsinogen?
Trypsin
What do peptidases do? Where are they found?
On the epithelial cells of the SI, they convert peptides to single amino acids
What are the pancreatic lipases
- pancreatic lipase
- non specific esterase
- prophospholipase A2
- procolipase
What stimulates bicarbonate secretion? Where does this come from?
- stimulated by secretin
- potentiated by CCK
What does bile contain
- bile acids and salts
- phospholipids and cholesterol
- bile pigments from Hb breakdown - bilirubin
- inorganic ions - cations more prevalent as rest of as bile acidshas negative charge
Where is bile secreted from
The hepatocytes actively secrete bile components
What converts trypsinogen to trypsin
Enterokinase
