GIT Lec 4: Pancreas Flashcards
pancreas is a … gland
exocrine + endocrine
pancreas exocrine function
- produces secretions into gut
- source for most digestive enzymes (carbohydrates, protein, fat, NAs)
- enzymes produced in excess
- pancreatic function must be above 10% (digestive/absorption issues bellow that)
- secretion of HCO3- to neutralize stomach acid (needed for enzyme function)
pancreas endocrine function
-produces hormones that regulate entire body (eg. insulin)
exocrine- anatomy of pancreas
-secrete substances on apical side into ducts that drain onto epithelial layer
endocrine- anatomy of pancreas
-ductless gland, secretion across basolateral surface of diffusion into blood
pancreatic ducts
-similar to salivary gland
acinar cells- pancreatic ducts
-secrete digestive enzymes- exocytosis
duct cells- pancreatic ducts
-secrete H2O +HCO3-
pancreatic juices description
-isotonic, alkaline
how much pancreatic juices are produced a day
1-2 L/day
pancreatic juices electrolytes balance
- high HCO3-, low Cl-
- HCO3-/H2O secreted by duct cells
pancreatic juices enzymes description
- secreted by acinar cells
- proteolytic enzymes stored + secreted in inactive forms
- activation in duodenum by HCO3-
Ductular cell secretion- cytosol
- carbonic anhydrase (CA) converts CO2 + H2O into H2CO3 then dissociates H + HCO3-
Ductular cell secretion- apical side
- HCO3-/Cl- exchanger –> HCO3- out, Cl- into cell
- chloride channel (CFTR) –> Cl- out
Ductular cell secretion- basolateral
- Na+/H+ exchanger –> H+out, Na+ in
- Na+/K+ ATPase –> Na+ out, K+ in
- K+ channel –> K+ out
Ductular cell secretion- paracellular
- H2O +Na+ into duct because electrochemical gradient
after big meal: alkaline tide
-partial cells in stomach produces lots of acid so increased HCO3- in basolateral/blood
after big meal: acid tide
-duct cells produces lots of HCO3- so increased H+ in basolateral/blood
HCO3- from stomach and H+ from pancreas meet
in portal vein and maintain acid/base balance
starvation would occur without pancreas because
it is the source for digestive enzymes
proteases
-digest proteins into peptides/a.a
amylolytic enzymes
-digest starch into sugars
lipases
-digest triglycerides into free fatty acids and monoglycerides
nucleases
-digest NAs into free nucleotides
acinar cells produce
pro-enzymes into zymogen granules (vesicles) stored on apical side
acinar cells secretion into duct modulated by
-neurohormonal input
trypsinogen is secreted by
pancreas
trypsinogen—-> trypsin by
-membrane bound enterokinase in duodenum
trypsin is a protease and also activates
other proteases
In cystic fibrosis
Cl-/HCO3-exchanger is mutated
cystic fibrosis patients suffer
-pancreatic insufficiency
enzymes still produced by HCO3-/H2O minimal and enzymes cause pancreatic autodigestion
cystic fibrosis treatments
digestive enzymes +antacids
proteases by pancreas (inactive enzyme) and end-products
- trypsinogen
- chymotrypsinogen
- pro-elastase
- pro-carboxypeptidase A & B
-mixture of peptides and amino acids
-trypsinogen activated by … and active enzyme
- enterokinase
- trypsin
trypsin action
endopeptidase
chymotrypsinogen activated by … and active enzyme
- trypsin
- chymotrypsin
chymotrypsin action
endopeptidase
proelastase activated by … and active enzyme
- trypsin
- elastase
elastase action
endopeptidase
pro-carboxy peptidase A&B activated by … and active enzyme
- trypsin
- carboxypeptidase A & B
carboxypeptidase A & B action
exopeptidase
Amylolytic enzyme by pancreas (active enzyme) and end-products
- pancreatic amylase
- maltose,maltotriose, and a-limit dextrins
pancreatic amylase action
-cleaves starches to sugars
Lipolytic enzymes by pancreas (active enzymes) and end products
- lipase, free fatty acids and 2-monoglycerides
- cholesterol esterase, free fatty acids and cholesterol
lipase action
hydrolyzes triglycerides
cholesterol esterase action
-hydrolyzes cholesterols-esters
Lipolytic enzymes by pancreas (inactive enzyme) and end products
-prephospholipase A2, free fatty acids and lysophospholipids
prephospholipase A2 is activated by… and active enzyme
- trypsin
- phospholipase A2
phospholipase A2 action
hydrolyzes phospholipids
CCK regulation of pancreas
- fatty acids/a.a in small intestine triggers CCK secretion
- increase enzymes secretion, gall bladder contraction (relaxation of sphincter of Oddi
- negative feedback loop
secretin regulation of pancreas
- acid in duodenum
- decrease pH triggers secretin, and secretin increase HCO3- release from liver and pancreas
- negative feedback loop
secretin + CCK
- inhibit gastrin secretin
- reduced stomach motility
- reduced acid secretion
ach from parasymp nerves
increase enzymes secretion from pancreas
phases of pancreatic secretion regulation
- cephalic
- gastric
- intestinal (major)
intestinal phase of regulation (pancreatic secretion)
secretion + CCK release
gastric phase of regulation (pancreatic secretion)
distension of stomach stimulate pancreatic secretion via parasymp. nerves
cephalic phase of regulation (pancreatic secretion)
sight, smell, taste –> parasympathetic
