Regulation of Pancreatic Secretion

Three basic stimuli are important in causing pancreatic secretion:

1. The parasympathetic vagus nerve endings and from other cholinergic nerves in the enteric nervous system, stimulates releasing of enzymes.

2. Cholecystokinin stimulates the release of pancreatic enzymes.

3. Secretin stimulates the release of a large amount of sodium bicarbonate in the pancreatic juice.

Secretion of Bile by the Liver;

One of the many functions of the liver is to secrete bile, normally between 1000 ml/day.

Function of bile:

1) emulsifies fats,

2) activates lipase,

3)enhances intestinal motility,

4) transports fatty acids,

5) bactericidal action.

Composition of bile

Bile acids, bilirubin, fatty acids, cholesterol, salts, bicarbonates - pH 7.3 - 8.0 (vesicle bile has a pH of 6.0 since bicarbonates are absorbed together with water).

Regulation of liver activity
Bile secretion occurs continuously, in the absence of chyme in the duodenum, bile enters the gallbladder, where it concentrates.

Bile secretion occurs during digestion.

It is activated by the vagus nerve with the participation of conditioned, as well as unconditioned stimuli from the oral cavity, stomach, intestine.

Humoral substances: cholecystokinin, secretin, insulin, gastrin increase, but epinephrine, norepinephrine, glucagon inhibit bile secretion

Secretions of the Small Intestine

All parts of the small intestine: duodenum, jejunum and ileum secretien small intestinal juice, pH 7.0-8.6, contains water, salts, mucus, urinary and lactic acid, more than 20 enzymes that complete the cleavage of nutrients on the membranes of the brush border - Membrane digestion.

Regulation of Small Intestine- Secretion—Local Stimuli
By far the most important means for regulating small intestine secretion are local enteric nervous reflexes, especially reflexes initiated by tactile or irritative stimuli from the chyme in the intestines.