Pancreas: Histo and Physio Flashcards
definies head/neck of pancreas?
gastroduodenal a.
a. behind neck
SMA merges emerges at inferior border
tail of pancreas
TV12
invested in splenophrenic ligemanent
may be injured during splenectomy
Main duct “wirsung”
comes from ventral bud and distal dorsal bud, more inferior
accessory duct “Santorini”
comes from proximal dorsal bud - drains superior portion of head
exocrine pancreas
- acinar cells: secrete zymogens, amylase, lipase, trypsinogen (pancreatic enzymes)
- ductal cells: secrete H20 and bicarb
Centroacinar cells: duct cells that secrete HCO3
- final digestive juice is alkaline and isosmotic.
Endocrine pancreas
islets of langerhans Alpha cells: glucagon Betal cells: insulin delta cells: somatostatin PP cells: pancreatic polypeptide: stimulates gastric chief cells, inhibits bile secretion and inhibits pancreatic enzymes and HCO3- secretion
inhibited by sympathetics
stimulated by PS
secretin
acts locally and increases HCO3- secretion and pancreatic enzyme secretion
- secretin is activated by high acidic content in the duodenum
motilin
increases gastric and intestinal motility
islet-acinar axis
means by which blood sugar regulates release of glucose
- comunication b/w all cells randomly arranged around vessels - all cells see blood
CCK
- activated by fats/proteins in the duodenum
stimulates the release of enzymes from acinar cells - Lipase is most important, because it is the only enzyme kthat can digest fat
pancreatic juice
secretion is opposite to that of the stomach, it is very alkaline
includes aqueous bicarb. and pancreatic enzymes
Aqueous Bicarb
secreted by duct cells of pancreas
stimulated by secretin
promotes NAHCO3- co transport
buffers pH for maximum enzyme activity, prevents damage to mucosa
Pancreatic enzymes
secreted by acinar cells
for digestion of meal and absorption of nutrients
includes: amylase, trypsinogen and most impiortantly lipase
stimulated by CCK
Amylase
acinar cell secretion
requires CL- to activate
break down of starch and glycogen
Trypsinogen
acinar cell secretion
activated by enteropeptidase
breaks down protein polypeptides
Lipase
MOST IMPORTANT ENZYME OF PANCREAS!
cant digest fats without it
product of acinar cells
breaks down triglycerides
enterokinase
needed to convert trypsiongen to trypsin
found in brush border of duodenal enterocytes
how is pancreatic secretion regulated?
secretin, increases HCO3- (based on pH levels)
CCK increases enzyme secretion (based on fat/protein levels in duodenum)
what factors cause CCK release?
CCK stored in I cells
- when GA’s and AA’s are in stomach, CCK-RP and MP are released : these are required to activate CCK
- CCK digests proteins and CCK-RP and MP, thus when no proteins/fats are in duodenum, CCK digests its own activator.
- no trypsinogen is released
factors causing secretin release?
- released from S cells in duodenal mucosa
- S cells are pH meters
when pH drops, S cells secrete secretin, which stimulates ductal cells to increase bicarb. secretion
duodenal ulcer
not enough secretin being released
or could be due to no acid in stomach, which also results in no secretin release
steatorrhea
fat in stool
early sign of pancreatic dysfunction
reduced lipase and bicarb. secretion
acute pancreatitis
obstructive: gallstones/ malignancy
retention of secretion in pancreas, digestion of pancreatic tissue
chronic pancreatitis
mutated trypsin - not responsive to trypsin inhibitor
resutls in inflammation of pancreatic tissue
- could also be due to alcohol abuse
Pancreatic polypeptide
stimulates gastric chief cells
inhibits bile secretion and inhibits pancreatic enzymes and HCO3- secretion
vasoactive intestinal peptide (VIP)
similar to action of glucagon
secreted by delta-1 cells
increases pancreatic exocrine secretion
Motilin
increases gastric and intesinal motility
secreted by EC beta cells along with secretin
