QS Study

Gastric Juice is the mixture of secretions from all the glands present in the stomach. It is most helpful in the digestion of food. It consists of Enzymes present in the stomach. It helps in absorbing the food in the body very easily. Gastrin stimulates acid secretion by stimulating histamine release from ECL cells. When the pH of the stomach gets too low, somatostatin secretion is stimulated.

Basic Functions of Gastric Juice –

  • Presence of HCL makes the juice antiseptic, killing almost all the germs entering with food
  • Pepsinogens are converted to pepsins with the help of HCL and help in protein digestion

Gastric juice secretion is regulated by –

i) Neural mechanism,

ii) Humoral mechanism

(1) Neural mechanism – The neural components are –

  • Local autonomic reflexes, involving cholinergic neurons
  • Impulses from CNS by way of the vagus

Fig: a Postulated mechanism for the secretion of hydrochloric acid

Cephalic influences –

  • The presence of food in the mouth reflexly stimulates gastric secretion.
  • Sight, smell and thought of food increase gastric secretion.
  • This is responsible for 1/3 to 1/2 of the acid secretion.

Gastric influence –

Acceleration of gastric secretion is caused by –

  • Food in stomach
  • Stretch of the wall and chemical stimuli of a receptor.

Intestinal influence –

Fats, CHO, and acid in the duodenum inhibit gastric secretion by a neural mechanism.

 

(2) Humoral mechanism –

(a) Stimulation by gastrin: Nerve signal from the vagi and the local reflexes also cause the secretion of gastrin hormone. It causes –

  • Secretion of HCl by parietal cells to increase eight times.
  • Secretion of enzymes by peptic cell to increase 2 to 4 times.

(b) Histamine secretion: It stimulates acid secretion.

(c) Others substance: A few substances stimulate the gastric secretory cells. This are-Hypoglycemia, Alcohol, Caffeine etc.

When gastric pH is below 3.0, there is a feedback inhibition of gastrin secretion.

It helps in – Protection of gastric mucosa and action of peptic enzymes.