Tubular glands which extend from the bottom of the gastric foveola
to the muscularis mucosa. On the basis of their location, the gastric glands
are divided into cardiac glands which are short and tortuous and the fundic
glands which are straight slender glands with narrow lumen and made up
of Mucous cells, pepsinogen or chief cells and parietal or exyntic cells. The
pyloric glands in the pyloric region of the stomach are short and tortuous.
Stimulation of parasympathetic vagus gives rise to secretion of the gastric
juice rich in acid and enzymes. It also increases gastric secretion. The
secretion is mediated through release of acetylchlorine.
GASTRIC JUICE AND THE SECRETION
The gastric juice is the product of surface epithelium and the various
glands. The volume of the gastric juice secreted in man is 1200 – 1500ml
per day, pH become 2-3 when the gastric juice mixes with the food.
Specific gravity is 1.002 – 1.004.
The major constituents are water, HCl, enzymes – pepsin, rennin,
gastric lipase, gelatinase and mucus, electrolytes as sodium, potassium,
calcium, phosphate, bicarbonate and sulphate.
Hydrochloric acid is secreted by oxyntic cells parietal cells or
secreting cells. These contain small channels called canaliculi which
communicate with the lumen of the gastric gland. The HCl is secreted by
the membrane of these canaliculi. It is an active process involving
expenditure of energy, O2 utilization, CO2 evolution and enzymes systems
participation. Secretion of 1gm molecular weight of HCl requires
expenditure of 10,000 gram calories of energy. The source for hydrogen
ions is water and the source for chloride ions is Nacl of blood. Hydrogen
ions are formed by dissociation of water into hydrogen and Hydroxyl ions.
This is the main source of hydrogen ions. The hydrogen ions combines
with OH ions H2O and HCO3 ions are released into the interstitial fluid and
In a simple way, the reactions involved are,
CO2 + H2 +NaCl