physio:5
Date @April 28, 2024
status 1 Summrize
URL 1 https://t.me/c/1684021833/252998
FROM A.S
important to know that
HCl not essential for activate pepsinogen {HCL just enhance the
activation}
while pepsin is essential for activation of pepsinogen {but in slow rate}
pancreas
has endocrine and exocrine function
endocrine function hah been discussed in endocrine module
now about exocrine function
exocrine secretion secrete in duodenum by common bile duct which
is dangerous area for obstruction
pancreatic juice
physio:5 1
alkaline PH=8 and 1.5L per day
composition of pancreatic juice
1. 98.5% water
2. 1.5% solids
a. inorganic Na HCO3 mainly
b. organic like trypsin inhibitor and CO-lipase and some enzymes
function of pancreatic juice
1. secretion of sodium bicarbonate
1. to neutralize acidic chyme to prevent duodenal ulcer
2. to adjusts PH for action of pancreatic enzymes
mechanism of NaHCO3 secretion
it secreted in duct of the gland by duct cells not in acini
at the same time of HCO3 secretion in duct lumen, H+ secreted
in blood and that makes post prandial acidic tide, which will
neutralize with postprandial alkaline tide of stomach
also at the same time of HCO3 secret in lumen CL decrease in
lumen
so post prandial acidic tide happen with pancreatic juice, while post
prandial alkaline tide happen with gastric juice
2. digestion of food molecules
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3. wash out of pancreatic enzyme to protect pancreas from eating himself
flow rate of pancreatic juice {practical}
after intake food flow rate of pancreatic juice increase from
0.2ml/minute to 4ml/minute
HCO3 increase in lumen and CL— decrease
causes
1. secrtin-acetyle choline in ductular cell that increase volume of juice
by increase HCO3 and H2O and decrease CL
2. CCK increase enzymes secretion of pancreatic juice
pancreatic enzymes
some pancreatic enzymes secret in inactive form called zymogens and
need anther enzymes to active
1. pancreatic amylase enzyme
it is alpha amylase enzyme, while beta amylase enzyme secrete in
saliva
beta amylase doesn’t digest food well because low time of
chewing of food then swallowing it to low PH in stomachs so it
stop working ,
while alpha amylase take all its time in digest because more time
of food in intestine which has perfect PH for alpha amylase work
{mcq}
physio:5 3
pancreatic amylase digest starch into disaccharides and
trisaccharides, but gives more disaccharides than trisaccharides,
so pancreatic amylase doesn’t completely digest starch {mcq}
pancreatic amylase enzyme activated by CL
2. pancreatic lipase enzyme
pancreatic lipase activated by bile salt and co-lipase {mcq}
it turn Triglyceride into Fatty acid and glycerol and monoglyceride
so pancreatic lipase completely digest of lipid
3. cholesterol-esterase enzyme
it turn cholesterol esters into cholesterol and fatty acids
4. trypsin enzyme
secret in inactive {zymogen} form called trypsinogen which
activated by enterokinase enzyme {from intestinal cell} into trypsin
trypsin also activate trypsinogen {autoactivation}
trypsin also activate other enzymes like chymotrypsinogen and
carboxypeptidase
while trypsin inhibitor enzyme inhibit activation of trypsinogen in
pancreas {mcq}, so deficiency in trypsin inhibitor lead to
pancreatitis
trypsin is endopeptidase enzyme so it give polypeptides and
dipeptide {not amino acids}
also chymotrypsin is endopeptidase enzyme so it give polypeptides
and dipeptide {not amino acids}
while carboxypeptidase enzyme is exopeptidase enzyme so it
gives amino acids
NB: endopeptidases help exopeptidases because exopeptidases
brake down protein into small molecules to facilitated its brake down
by endopeptidases into amino acids
NB: chymotrypsin use in eating inflamed tissue but must take
intramuscular and do sensitivity test
5. carboxypeptidase enzyme
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also secret in inactive form and activate by tyrosine
carboxypeptidase enzyme is exopeptidase enzyme so it gives
amino acids
control of pancreatic secretion
1. nervous control
a. vegal stimulation
vegus stimulated by condition reflex like smell or thinking of
food
unconditional like food in mouth and stomach
vegus make secretion {small in volume/poor in bicarb/rich in
enzyme}
b. sympathetic
2. hormonal control
a. secretin
unlike vegus, secretin make secretion {large in volume/rich in
bicarb/poor in enzyme}
b. CKK
like vegus make secretion {small in volume/poor in bicarb/rich in
enzyme}
NB: secretion of pancreatic juice stop by Preventing acidic chyme from
arriving to duodenum
1. stop eating
2. nasogasrtic tube {ryle tube} to take of any juice in stomach
regulation of exocrine pancreatic secretion
1. cephalic phase {nervous}
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1. occur before food reach stomach
2. cephalic phase {nervous} response for 20% of secretion {mcq}
3. stimulate pancreatic juice through condition and unconditional
2. gastric phase {nervous and hormonal}
1. occur when food enter the stomach
2. stimulate pancreatic secretion by vago-vegal reflex
3. also stimulate pancreatic secretion by gastrin secretion
3. intestinal phase {hormonal}
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1. it is main phase, response for 80% of secretion
2. occurs when food reach intestine
3. occur through secretin and CCK
about secretin hormone
it secreted from S cells from duodenum
it release stimulates by acid food chyme
action of secretin hormone
1. secretion of pancreatin juice {large in volume/rich in bicarb/poor in
enzyme}
2. it decrease rate of gastric emptying and decrease gastric acid
secretion
3. it decrease intestinal motility
4. increase HCO3 secretion from biliary system
about cholecystokinin CCK hormone
physio:5 7
it secreted from I cells from Duodenum
it release stimulates by protein digestive product and fatty acids
action of CCK hormone
1. secretion of pancreatin juice {small in volume/poor in bicarb/rich in
enzyme}
2. from its name it help in evacuation of gallbladder and relaxation of
sphincter of oddi
3. increase intestinal motility {unlike secretin}
4. it decrease rate of gastric emptying {like secretin}
physio:5 8
