 Exocrine Secretion of Stomach responsible for
digjustive process.
Composition
2-2.5 liters per day is produced
pH 1-2
water 99.5 %
Solid 0.5 % Na+, K+, Mg++, Cl, HCO3, HPO4, SO4
• Increase rate of secretion decreases Na+ and H is high
• Decrease rate of secretion Na+ is high and H is low
o Pepsin produced by of the chief cells of
gastric glands in the form of pepsinogen.
o Pepsinogen is converted to pepsin in the
presence of HCL at pH of 2.
o G. lipase split fat little role in digestion of
fat.
o G. Geletinase liquefy gelatin
o G. Amylase CHO digestion
o Lysozyme bactericidal
o Carbonic anhydrase
SOLUBLE MUCIN:
Thin layer produced by pyloric and cardiac
glands
INSOLUBLE MUCIN:
Produced by foveolar cells and covers the
entire gastric mucosa
INTRINSIC FACTOR:
Produced by Parital cells responsible for
B12 absorption.
 Parietal Cell is fine network of intercellular
canaliculi it increases hydrogen ions will
increase in HCL secretion which may go up to
155 meq/L which is 3 million time more than
plasma.
 Secretion is in two steps
i. Secretion of Hydrogen Ions
ii. Secretion of Chloride Ion
In P Cells following reaction occur.
CO2+ H2O ↔H2CO3 ↔H+ HCO3
 Hydrogen Ion is secreted in the lumen of canalculi
in K ion exchange by Na+ - K+ ATPase pump.
 HCO3 enters into the blood in exchange of cl
 HCO3 is responsible for Post perendial alkeline tide
characterized by alkaline urine and increase PCO2
and decrease breathing.
 HCO3 enters into pancreatic secretion in small
intestine to neutralize its acidity


Cl channel are present on apical
membrane of P cell
Cl channel are activated by
CAMP
H+ Cl → HCL

All this process is done by active
transportation and energy is
provided by the mitochondria
which are scattered in P.cells
 Vegal Stimulation, Gastrin Histamine increase the HCL
production.
 Low pH in Stomach, smatostatin, postaglandins (PGE,
PGI), Epithelial growth factor transforming growth
factor will decrease the HCL production.
Functions:
i. Breakdown of Protein
ii. Provide Environment Pepsin action
iii. Inhibits bacterial growth
 Chief Cell Produce it mainly and small amount is
produced by pyloric cell
 Chief cell produce pepsinogen I and pyloric cell produce
pepsinogen II
 Stored as zymogen granules at epical region of chief cell
 Pepsinogen is converted to pepsin in the presence of
HCL and pepsin further potentiate the conversion of
pepsinogen in pepsin
 Splits Proteins in proteases, peptones and polypeptides
 Optimal pH for action is to so HCL is most important
factors for the action of Pepsin
Mucus Secretion:
Insoluble mucus is produced mucus secreted cell of gastric
mucosa it is a gel like coat over mucosa which protect the
stomach from the attack of HCL.
Soluble Mucus is produced by mucus cell of pyloric and
cardiac glands
Intrinsic Factor
It is a glycoprotein produced by the P cells of the mucosa
Specially in the fundus region by cyclic AMP
Intrinsic factor combines with vitamin B 12 and complex is
formed which absorb the Vitamin B 12 in small intestine
Neural
 Vagal stimulation will increase HCL production by
accting on P Cell which causes through release of Ach.
 Ach potentiate the effect of histamine on H2 receptors.
 GRP ( Gastric Release Peptide) is produced which
causes release of HCL
 Somatostatin is inhibited by vagal stimulation
 Ach acts on enterochromoffin like cell which acts on
histamine which increases H ions by acting on H2
receptors
Gastrin
• G cell produce it and it goes into the blood and then reaches to stomach and causes
increase production of pepsin and HCL by acting on P cell and chief cell.
• Gastrin is produced in progastrin from which is inactive and activated by HCL and
digestive enzyme.
• Gastrin of three types.
i.
G14
ii.
G17
iii.
G34
 G17 is the main type with half life of two to three minutes and it is inactivated by
kidney and small intestine
Mechanism of action :
Gastrin acts on CCk- β/ gastrin receptors on P cells and open calcium channel this
increase in H ion by opening of Ca++ channels under the effect of Na+, K+ ATPase
pimp.
Gastrin increase histamine which causes increase in HCL
Vagal Stimulation distension pyloric
entrum, Product of digestion, Ca+ and
epinephrine increases the production of
gastrin.
While low pH of gastric Juice,
somatostatin, secretin, gastrin inhibitory
peptide, VIP, glucagon and calcitonin
decrease the production of gastrin.
Cephalic Phase
By smell sight and thought gastric juice is produce.
about 500 ml/h of gastric juice is produce by this
phase.
1.
2. Gastric phase
200 ml/h of gastric juice is produce by the presence of
food in the stomach due to distention of stomach ,
products of digestion and low pH will produce gastrin
release and ultimately gastric juice production is increase.
Distention of small intestine, presence of acidic food in the
intestine inhibits gastric secretion by intarogastric reflex release
of secretin GIP, VIP CCK inhibits the gastrin release.