The Endocrine Pancreas Flashcards
What fuses to form pancreas
2 pancreatic buds at junction of foregut and midgut
The pancreas is posterior to ____ curvature of stomach
greater
How long is the pancreas
12-15cm
Where do the larger ducts travel?
Connect to common bile duct form liver and gallbladder, then enter duodenum as a common duct through the the hepatopancreatic ampulla
Pancreas is formed of small clusters of ___ epithelial cells
glandular
the clusters of cells in the pancreas are called
acini
Exocrine activity of pancreas is performed by
acinar cells (make and secrete fluid and digestive enzymes = pancreatic juice)
Endocrine activity of pancreas is performed by
Islet cells (make release several peptide hormones into portal vein)
What digestive enzymes does the pancreas release?
Amylase - carb
Trypsin, chymotrypsin, elastase - protein
Lipase - triglycerides
What is the site of insulin and glucagon secretion in the endocrine pancreas?
Islet of Langerhans
What cells secret glucagon?
alpha cells
What cells secrete insulin
Beta cells
What cells secrete somatostatin (SST)
Detta cell
What is paracrine “crosstalk” in pancreas?
Communication between alpha and beta cells (local insulin release inhibits glucagon)
Role of insulin
Stimulates glucose uptake in to cells and carb catabolism.
Stimulates lipid synthesis by adipose tissue and stimulates protein synthesis
Role of glucagon
Glycogenolysis in liver
Lipid hydrolysis in adipose tissue which leads to increase ketogenesis
Increase gluconeogenesis from available amino acids
What does insulin suppress?
Lipolysis
Breakdown of muscle (decreased ketogenesis)
Glycogenolysis
Gluconeogenesis
Glucagon inrcreases
hepatic glucose output (increased glycogenolysis, increased gluconeogenesis)
Peripheral release of gluconeogenic precursors (lipolysis, muscle glycogenolysis and breakdown)
Pathway of insulin secretion in beta cell
Glucose enters cell via GLUT2 glucose transporter (amount depends on conc. of glucose)
Glucokinase activated
The glucose is phosphorylated to glucose 6-phosphate
Rate of glycolysis is increased
ATP generated, closes KATP channel, stopping efflux of K+.
Membrane becomes depolarised, allowing opening of voltage-dependent calcium channels
Rapid influx of calcium
Triggers insulin exocytosis.
What is stored together with insulin in secretory granules and released in equimolar concentration
C-peptide
Proinsulin contains alpha and beta chains of insulin, joined by the C-peptide.
Presence implies endogenous insulin production
Biphasic insulin release
B-cells sense rising glucose and aim to metabolise it
1st phase = Rapid release of stored products
2nd phase = slower release of newly synthesised hormone
Insulin action in muscle and fat cells
GLUT4 insulin receptor is a high affinity large transmembrane glycoprotein
Mechanisms not fully understood.
Causes exocytosis of GLUT4 vesicles, increasing glucose transporter in cell membrane and rapid uptake of glucose.
What is a short-term glucose buffer
Liver glycogen
(Glucose concentrations in portal venous blood can eaily reach 20mM after a meal.
Much of this removed by liver
Insulin allows peripheral muscle and adipose tissue to take up glucose from the circulation
Some of the surplus glucose is stored locally as glycogen, but it is mostly converted into fats)
Where are glucose sensors located?
Pancreatic islets
Medulla, hypothalamus and carotid bodies
Inputs from eye, nose, taste buds
Sensory cells in gut wall (incretins)
