L4 - pancreas secretions Flashcards
function of pancreas
- exocrine - secretes pancreatic juice
- endocrine- secretes hormones of insulin and glycagon
function of pancreatic juice
has enzyme rich secretion and alkaline secretion
- enzymes used for digestion
- alkaline secretion neutralising the pH and for protection of intestinal mucosa
structure of the prancreas
acinar cells > acinus or secretory unit>lobule
pathway of the pancreatic juice from the pncreas into the duodenum
from acinar cells > intercalculated ducts > intralobular duct > interlobular ducts > main pancreatic ducts
- the pancreatic ducts merge with the common bile duct
- both juice and bile’s flow is controlled by the sphincter of Odii.
types of pancreatic cell types
- acinar
- duct
- centroacinar
- goblet
function of acinar cells
- produces and exports proteins like digestive enzymes
- stimulated CCK rececptors and ACH receptors leads to increased enzyme secretion
function of duct cells
transports electrolytes and secretes HCO3 rich fluid for alkalinisation and hydration of the proteins secretions produced by the acinar cells
function of centroacinar cells
located at the junctio of acinar and duct cells
-function not sure
function of goblet cells
-produces mucus for lubrication, hydration, mechanical protection of epithelial cells
how is acinar cell stimulated and what happens
- ACh and CCK activate PKC (protein kinase ) and leads to Ca2+ influx. This leads to vesicles containing enzymes being released by exocytosis
- VIP and secretin activate adenylyl cyclas which produces cAMP and activates PKA
- also stimulates gallbladder to release bile into the duodenum
mechanism of secreting HCO3 rich fluid from the Centro acinar and duct cells
- CO2 diffuses into the cells and react with water to make CA
- CA dissociates into HCO3 and H ions
- HCO 3 transported out by Hco3- cl exchanger and the H ions are secreted into the blood
- the H ions helps to neutralise the alkaline tide in the blood caused by the stomach as it secretes acid
what anion channel does the mechanism of HCO3 rich fluid depend on
- Cl- ions
- the ions are transported out of the cell into the lumen of the pancreas through CFTR (regulated by cAMP
- this allows the CL- ions to be transported back into the cells for exchange of HCO3 ions
-
location of CFTR
on apical plasma membrane of pancreatic cells
how is CFTR channels regulated
by secretin or increase in cAMP
-increasing the no of open channels
how does a defect in CFTR leads to symptoms of cystic fibrosis
- reduced HCO3- secretion and water by the ducts
- leads to malnutrition