Steps of Fat Digestion:
Almost all the fats going to the digestive tract is hydrolyzed into triglycerides. Only a small fraction of dietary fat consist of cholesterol esters and phospholipids. Although fats are hydrolyzed primarily in the upper small intestine by the action of pancreatic lipase, some digestion of triglycerides may take place in the stomach.
Much of the lipolytic activity of gastric contents is due to lipase secreted by the lingual serous glands located in the back of the tongue. This lingual lipase is most active on medium and short chain triglycerides. It also appears to prepare dietary fat for more efficient digestion in the small intestines.
Lingual lipase is believed to be particularly important in the digestion in the new born. Human breast milk also contains a lipase that contributes to fat digestion in the young infant. An additional lipase may be secreted by the stomach but appears to be insignificant on fat digestion.
Steps of Fat Absorption:
In the lumen of the small intestines, the free fatty acids, monoglycerides, some diglycerides and triglycerides and cholesterol are mixed with bile salt to form micelles. These water-soluble microscopic particles can penetrate the mucosal membrane. Most of the absorption of fats occurs from the jejunum.
Fatty acids that contain 12 carbon atoms or fewer are absorbed into the portal circulation without reesterification in the mucosal cell. They are attached to albumin for their transportation and they may be used within the liver or released to other tissues in the body. The glycerol resulting from fat hydrolysis is also carried by the portal circulation.