Question

In your own words, describe the physiologic functions of the following gastric secretions: hydrochloric acid, pepsin, gastric lipase, intrinsic factor. In your own words, describe the stages of gastric activity: cephalic, gastric, and intestinal.

Answer 1

Enzymes
1)Hydrochloric acid
It activates the Pepsinogen and help in digestion of proteins .
It also eliminates the bacteria
and other organism from the body .

2). Pepsinogen (inactive) convert into active pepsin with the help of Hydrochloric acid
optimal pH = 2 is required  
It helps to digest proteins.

3).Gastric lipase -weak fat splitting enzyme from stomach;
optimal pH is 4-4.5 and it is inactivated at pH 2.5.

4).Intrinsic factor --> It is secred by parietal ( Oxyntic cells of stomach ).It combines with Vitamin B 12 and it is absorbed through terminal Ileum .
So it helps in absorption of Vitamin B12 .

Phases of gastric secretion
**Cephalic Phase  
(1) It occurs even before food enters the stomach i.e. psychic stimulation of gastric juice in response to sight, smell, thought or taste of the food.

(2) Its influences on gastric juice Its influences on gastric juice secretion secretion are vagally mediated responses induced by activity in central nervous system .

(3)It accounts for approx. 30-50% of the total gastric juice secretion normally .

**Gastric phase
(1) It occurs once food enters the stomach .

(2) Its influences on gastric juice secretion are primarily local reflex responses and responses induced by activity in response to gastrin.

(3)It accounts for 50-60% of total gastric juice secretion .

** Intestinal Phase

(1)It occurs when food enters the duodenum.

(2) Its influences on gastric juice secretion are the reflex and humoral feedback effects initiated from the mucosa of the small intestine

(3) Its contribution to gastric juice secretion of the total gastric juice secretion is much less as compared to cephalic and gastric normally.