Case 3 - Yaffas Flashcards
what are the pancreatic digestive enzymes secreted by
pancreatic acini
what is secreted by the small ductules and larger ducts leading from the acini
large volumes of sodium bicarbonate solution
what happens to this combination of enzymes and sodium bicarbonate
flows through a long pancreatic duct that normally joins the hepatic/bile duct immediately before it empties into the duodenum
what does this solution enter the duodenum through
the papilla of Vater surrounded by the sphincter of Oddi
when is pancreatic juice secreted most abundantly
in response to the presence of chyme in the duodenum
what is secreted from the endocrine pancreas
insulin and glucagon
what is insulin secretefd by
beta cells of the islet of langerhans
what is glucagon secreted by
alpha cells of the islet of langerhans
where are insulin and glucagon secreted into
directly into the blood
what is the fundamental secretory unit of the endocrine pancreas
composed of an acinus and an intercalated duct, merged to form intralobular ducts, which in turn merge to form interlobular ducts, and then the main pancreatic duct
what does pancreatic secretion contain
digestive enzymes
bicarbonate ions
water
what are the three protein digestive enzymes secreted by the pancreas
trypsin
chymotrypsin
carboxypolypetidase
describe trypsin
the most abundant of the protein digestive enzymes to be secreted. It splits whole and partially digested proteins into peptides of various sizes but do not cause release of individual amino acids.
describe chymotrypsin
It splits whole and partially digested proteins into peptides of various sizes but do not cause release of individual amino acids.
describe carboxypolypetidase
this splits peptides into individual amino acids, thus completing the digestion of some proteins all the way to the amino acid state.
what is the inactive form of proteolytic enzymes termed
zymogens
when is trypsinogen activated
activated by the enzyme enterokinase
it can also be autocatically activated by trypsin that has already formed from previously secreted trypsinogen
where is enterokinase secreted from
intestinal mucosa when chyme comes into contact with the mucosa
what is chymotrypsinogen activated and what does it form
activated by trypsin to form chymotrypsin
what is Procarboxypolypeptidase activated by and what does if form
Activated by trypsin to form carboxypolypeptidase.
when do they all become activated
only become activated after they are secreted into the intestinal tract
what does secretion of trypsin inhibitor cause
prevents digestion of the pancreas itself
what is important about the secretion of this trypsin inhibitor
it is important that the proteolytic enzymes of the pancreatic juice do not become activated until after they have been secreted into the intestine because the trypsin and the other enzymes would digest the pancreas itself
where is trypsin inhibitor formed and what does it do
in the cytoplasm of the glandular cells, and it prevents the activation of trypsin both inside the secretory cells and in the acini and ducts of the pancreas
what can happen if a duct is blocked
large quantities of pancreatic secretion can be pooled in the damaged areas.
under these conditions, the effect of trypsin inhibitor is often overwhelmed in which case the pancreatic secretions rapidly become activated, thus causing digestion of the pancreas
what is this event called
acute pancreatitis
what do acetylcholine and cholecystokinin do
stimulate the acinar cells to secrete large quantities of pancreatic digestive enzymes but relatively small quantities of water and electrolytes to go with the enzymes
what does secretin do
stimulates ductal epithelial cells to secrete large quantities of water solution of sodium bicarbonate
pathways for stimulating the insertion of zymogen granules and thus releasing digestive enzymes
ACh and CCK both activate Gαq, which stimulates PLC, which ultimately leads to the activation of PKC and the release of Ca2+.
Elevated [Ca2+]i also activates calmodulin (CaM), which can activate protein kinases (PK) and phosphatases (PP).
Finally, VIP and secretin both activate Gαs, which stimulates adenylyl cyclase (AC), leading to the production of cAMP and the activation of PKA.
The duct cells have receptors for secretin, GRP, all of which stimulate HCO3- secretion.
The duct cells have receptors for substance P which inhibits HCO3- secretion.
what does sodium bicarbonate do
causes neutralisation of HCL
what is CCk released by
I-cells in the duodenal and upper jejunal mucosa
what does lactase do
splits lactose into galactose and glucose
what does sucrase do
splits sucrose into fructose and glucose
what does maltase do
splits maltose into multiple molecules of glucose
what does alpha-dextrinase do
splits small glucose polymers into multiple molecules of glucose
where are these enzymes located
in the enterocytes
what do bile salts do to prevent further digestion
they form a micelle, around the fat globule that is to be digested
these develop because of the hydrophilic and hydrophobic nature of bile salts
do triglycerides stimulate pancreatic secretion
they do not, but their hydrolytic products: monoglycerides and free fatty acids do
how are vitamin b12 and intrinsic factor absorbed
endocytosis
what is absorbed in the ileum
vitamin B12 and bile salts
what are the three levels of the surface area of the small intestine
- folds of Kerckring
- villi (+ crypts of Lieberkuhn)
- microvilli
why does referred pain occur
due to convergence on second order neurones.
the same spinothalamic pathways carry nerves form adjacent skin and muscles - ‘visceromotor convergence’
the brain misinterprets the signals that originate from internal organs as coming from co-inervated somatic regions
