18.10 PANCREATIC ISLETS Flashcards
What kind of gland is the pancreas (endocrine or exocrine)
both
99% of the exocrine cells of the pancreas are arranged in clusters called?
acini
What do the acini produce?
digestive enzymes, which flow into the GI tract through a network of ducts
Scattered among the exocrine acini are 1-2 million tiny clusters of endocrine tissue called
pancreatic islets (or islets of langerhans)
each pancreatic islet includes 4 types of hormone secreting cells which are?
- alpha or A cells
- beta or B cells
- delta or D cells
- F cells
Which cell constitutes 70% of pancreatic islet cells
Beta or B cells
Which cell constitutes about 17% of pancreatic islets
alpha or A cells
which cell constitutes about 7 % of pancreatic islet cells?
delta or D cells
What do alpha cells secrete?
glucogen
what do beta cells secrete
insulin
what do delta cells secrete
somatostatin
what do F cells secrete
pancreatic polypeptide
what does somatostatin do?
-acts in a paracrine matter to inhibit both insulin & glucagon release from neighboring A and B cells
-may also act as a circulating hormone to slow absorption of nutrients from the GI tract
-inhibits the secretion of growth hormone
What does pancreatic polypeptide do?
inhibits somatostatin secretion, gallbladder contraction & secretion of digestive enzymes by the pancreas
Hypoglycemia stimulates secretion of?
glucagon from alpha cells of the pancreatic islets
What does glucogen act on to accelerate the conversion of glycogen into glucose (glycogenolysis) & to promote formation of glucose from lactic acid and certain amino acids (gluconeogenesis)
hepatocytes (liver cells)
hyperglycaemia ____ the release of glucagon
inhibits (negative feedback)
hyperglycaemia stimulates secretion of?
insulin by beta cells of the pancreatic islets
INDIRECTLY what stimulates secretion of insulin because they act to elevate blood glucose? (2)
growth hormone (GH) and adrenocorticopic hormone (ACTH)
What is another way insulin secretion is stimulated by? the neurotransmitter?
acetylcholine - the neurotransmitter liberated from axon terminals of parasympathetic vagus nerve fibres that innervate the pancreatic islets
Which amino acids would be present in the blood at higher levels after a protein-containing meal?
arginine and leucine
What is a hormone released by enteroendorcine cells of the small intestine in response of glucose in the GI tract?
glucose-dependent insulinotropic peptide (GIP)
Digestion and absorption of food containing both carbohydrates & proteins provide?
strong stimulation for insulin release
What is glycogen secretion stimulated by? which division of the ANS
increased activity of the sympathetic division of the ANS
