pancreas and bile Flashcards
pancreatic duct
There is a main pancreatic duct that runs the entire length of the pancreas,
- the duct has several branches.
○ there are branches called interlobular ducts which go between lobules
○ and then intra lobular branches come off and they Feed into the lobules themselves
branching of the intralobular branches once in the lobules
once inside the lobule these Branch even further into intercalated ducts
- each one of these intercalated ducts ends up in an acinar
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what cells surround the duct
- surrounding the duct we’ve got pancreatic acinar cells which will secrete enzymes.
- But we’ve also got these Centro acinar cells ductile cells which secrete bicarbonate and water
why are ductule cells ciliated
if we look at these ductile cells, you can see that they are also ciliated and that’s important because the Cilia will move the Pancreatic juice through the ducts out towards the duodenum and the ileum,
- so these have got mitochondria to supply the energy for the movement of the Cilia.
the exocrine pancreas
pancreas secretes:
- enzymes
- bicarbonate + Na+, H20
The exocrine pancreas delivers its secretions of digestive enzymes, fluid, and bicarbonate ions to the duodenum following ingestion of food.
role of bicarbonate in pancreatic juice
important role in increasing the pH of the chyme entering the small intestine.
function of pancreatic juice - digestion of protein
the pancreas produces inactive precursors, and that’s really important because if these proteases Get activated within the pancreas then it will cause Auto digestion of the pancreas and inflammation and damage the pancreas.
○ So first of all - trypsinogen needs to be activated to trypsin and that’s by an enzyme called enterokinase which is produced by the cells of the duodenum
○ Once trypsin is produced it can then trigger the activation of chymotrypsinogen to chymotrypsin and also Pro carboxy peptidase into carboxy peptidase.
pancreatitis
autodigestion by enzymes
- inflammatory condiiton
- causes - gallstones, alcohol, toxins, hypertriglyceridaemia
function of pancreatic juice - digestion of carbs
pancreatic alpha-amylase
function of pancreatic juice - digestion of fat
pancreatic lipase (+bile salts)
function of pancreatic juice - neutralisation of gastric acid by bicarbonate
- protect mucosa
- optimum pH for enzymes (7)
how does secretin help in control of pancreatic secretion
Secretin stimulates the secretion of bicarbonate-rich pancreatic fluid.
- Secretin enters the intestinal lumen and stimulates bicarbonate secretion, ultimately neutralizing gastric H+, which plays an essential role in fat digestion by creating a more neutral (pH 6 to 8) environment.
bicarbonate release causes neutralization of the acidic environment, thus establishing a pH favorable for the action of digestive enzymes.
- Secretin increases bicarbonate secretion from duodenal Brunner’s gland as well
- negative feedback
how does cholecystokinin help in control of pancreatic secretion
- it is released in response to fatty acids and peptides
CCK stimulates pancreatic secretion by two possible mechanisms.
- First, CCK binds CCK-1 receptors on acinar cells and stimulates release of enzymes.
- second mechanism is indirect whereby CCK binds CCK-1 receptors on capsaicin-sensitive C-type vagal afferent fibers. Stimulation of vagal afferent nerves generates a signal that is sent to the medial nucleus tractus solitarius (NTS) located in the brain stem and eventually transmitted via cholinergic postganglionic vagal efferent fibers to the pancreas and other target organs. Acetylcholine released from the efferent nerve endings, binds M3 muscarinic receptors on the pancreatic acinar cells and causes release of pancreatic enzymes
- positive feedback
pancreatic insufficiency
incomplete digestion of fats and protein so get malabsorption
secretion of bicarbonate and water from the duct
secretion stimulated by secretin
- leads to increased cAMP
- Cl-/ HCO3 - channel activated by cAMP
