HCl hydrolises food stuff and also acts as antiseptic. HCl activates pepsinogen into pepsin, provides an acid medium for the action of pepsin, HCl in duodenum stimulates bile secretion and pancreatic secretion
Gastric renin coagulates caseinogen of milk and convers into casein
Gastric lipase digests fat
Excretion of toxins, heavy metals and drugs
Intrinsic fctor helps to absorv vit.B12
The extrinsic factor in the stomach is a factor for maturation of RBCs
Mucin forms a mechanical barrier preventing HCl and pepsin from digesting the mucos of the stomach itself
Mechanism of Gastric Secretion
Gastric juice is a mixture of secretion of different types of glandular cells in the stomach. During fasting, stomach secretes 10-60 ml /hr. After meal, the gastric juice is secreted increasingly
The secretion starts imediately after food and has maximum between 1 1/2 - 2 hours.
Then gradually declines and comes to fasting level after 3-4 hours
Different phases in gastric secretion
Nervous or cephalic phase
Nervous or Cephalic phase
During this phase the gastric secretion occurs even before the food reaches the stomach;
Both conditioned and unconditioned reflexes are involved.
Stimuli arise by the smell, sight, thoughts or hearing of food, and even in the absence of food in the stomach.
The higher centers are situated in the cerebral cortex and hypothalamus
The afferent nerves are those of special senses, such as olfactory, optic and auditory nerves.
The efferent nerves are vagus, and sympathetic nerves of coeliac plexus.
Non- conditioned reflexes
In this reflex, the gastric secretion occurs when food is being chewed in the mouth and is swallowed.
Here the gastric secretion occurs in the stomach even before the food enters the stomach; 50 to 100 ml is secreted
In this phase the gastric secretion occurs when the food enters the stomach. This gastric phase is controlled by two factors :
2. Hormonal factors
The nervous factor is the vagus reflex when the food enters the stomach, the wall is distended. This distension causes vagal stimulation and results in gastic secretion
The hormonal factor is gastrin. The distension of wall of the stomach causes release of gastrin from the mucosa. This gastrin is taken by the blood through the circulation brought back to gastric glands, which are stimulated by gastrin to secrete gastrin. 220 to 350 ml is secreted. This stage lasts for several hours
The presence of food in the small intestine also causes gastric secretion. The secretion starts after a latent period of 2-3 hours and continues for 8-10 hours. The sensory stimulation is caused by water, meat and partially digested food.
Gastric secretion also occurs at regular intervals even in fasting. It occurs by both nervous and hormonal factors.