Although a small amount of lipase is secreted by Ebner's glands on the tounge, and by the stomach, these digestive actions are not significant , as almost no real breakdown of fat occurs until the fats reach the
duodenum in the form of gastric chyme.
Fat Breakdown In The Small Intestines.
Fat digestion and absorption requires that the complex fat molecules be broken down into the smaller more manageable molecules. This is done by mixing the fat with the
digestive enzyme lipase, which
enters the duodenum from the pancreas - the main source of enzymes for digesting fats and proteins.
Lipase chops up lipid molecules into fatty acid molecules. However, because fat does not dissolve in water, the fat molecules enter the duodenum in a congealed mass, which makes it impossible for the pancreatic lipase enzymes to attack them, since lipase is a water soluble enzyme and can only attack the surface of the fat molecules. To overcome this problem the digestive system uses a substance called
bile, produced in the liver but stored in the
gallbladder, which enters the duodenum via the
bile duct. Bile
emulsifies fat - meaning, it disperses them into small droplets which then become suspended in the watery contents of the digestive tract.
Emulsification allows lipase to gain easier access to the fat molecules and thus accelerates their breakdown and digestion.
How Fat is Digested And Absorbed Into The Bloodstream.
Lipase and other digestive juices just break down the fat molecules into
fatty acids and types glycerol. Absorption of fat into the body, which takes 10-15 minutes, occurs in the
villi - the millions of finger-like projections which cover the walls of the small intestine. Inside each villus is a series of
lymph vessels (lacteals) and blood vessels (capillaries). The lacteals absorb the fatty acids and glycerol into the lymphatic system which eventually drains into the bloodstream. The fatty acids are transported via the bloodstream to the membranes of
adipose cells or muscle cells, where they are either stored or oxidised for energy.. Since glucose rather than fat is the body's preferred source of energy , and since only about 5 percent of absorbed fat ( the glycerols) can be converted into glucose, a significant proportion of digested fat typically stored as body fat in the adipose cells.
( Pictured Above left typical fat stored in adipose cells). The glycerol part is absorbed by the liver and is either converted into glucose (
gluconeogenesis), and/or used to help breakdown glucose into energy (
glycolosis).
Fat Loss Future Facts: #1 The Fat Gland
