The function of bile juice

What is bile juice? Bile is very important for proper digestion, it contains no enzymes. It is highly alkaline and helps neutralize the acid in the chyme as it leaves the stomach and enters the small intestine. This is necessary in order for the intestinal enzymes to function properly.

The function of bile juice

Bile is composed of bile salts, lecithin, cholesterol, and bile pigments. The first three are
involved in the emulsification of fat in the small intestine. The bile pigments give bile its color. 

The major bile pigment is bilirubin. Bilirubin is actually a breakdown product of hemoglobin, the oxygen-carrying protein in red blood cells. In the large intestine, bilirubin and other bile pigments are further converted by bacteria into brown pigments, which give rise to the color of faces.

If the bile duct is blocked so that the pigments cannot be excreted in the bile, they will be reabsorbed by the liver. Eventually, the pigments will accumulate in the blood and tissues, giving the skin a yellow color this condition is called jaundice. 

Cholesterol is a large fat-like molecule that has very low solubility in body fluids. This may lead to deposits of cholesterol in the heart and arteries, which could result in heart disease or arteriosclerosis. 

The liver excretes excess cholesterol in the bile. Gallstones result from the accumulation of excess insoluble cholesterol in the gallbladder.

Bile salts are the most active part of bile. They are salts of glycollic acid, which is made from cholesterol. Unlike cholesterol, bile salts are very soluble. These salts are essential for the 

digestion of fats. Butter and oil are fats that constitute part of a group of molecules called lipids.

Lipid molecules are insoluble in water and tend to coalesce to form globules. The enzymes that digest lipids, called lipase, can only work on the surface of these globules. Alone, it would take weeks for lipase to complete fat digestion in this manner. 

Bile salts solve this problem by having detergent-like properties - they coat the globules and break them up into millions of tiny droplets called micelles. This process, called emulsification, greatly increases the surface area exposed to attack by lipase, speeding up lipid digestion. 

Bile salts are conserved by the body, and are reabsorbed in the lower part of the intestine, carried back to the liver through the bloodstream, and secreted again.

Bile juice is stored
The liver, one of the body's largest organs, constantly secretes bile. (600 - 800 ml. a day) A network of ducts collects the bile and passes it to the gallbladder, where it is stored until needed.

The gallbladder is a small muscular sac that lies on the surface of the liver. When food enters the duodenum, certain receptor cells in the wall of the intestine since the presence of fats in the chyme. Stimulated by the fats, the receptor cells in the duodenum secretes a hormone, called cholecystokinin (CCK) into the bloodstream. 

This hormone causes inhibition of gastric motility and contraction of the gallbladder, forcing bile out through the bile duct and into the small intestine.

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