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Digestion of Fat

GASTROINTESTINAL PHYSIOLOGY

Epithelial celi

KEY

Triglycerides (longand short chain) Diglycerides (long and short chain)

[) ^cO Monoglycerides (long and short chain)

° Fatty acids (long and short chain)

3 Cholesterol Q Cholesterol esters Z> Carotene O Glycerol O O Na, K • • Mg, Ca 0=3 03 Solublo «=>-•=! Insoluble

Ficurf 7.37 Digestion of Fat-

Although some fat digestion hegjns in the mouth and stornach, most occurs in the intestine, largely by the action of panereatie lipases.

I ipases associated with the głycocalyx of the epithelial cells also eon-iribute to this process. The bile salts are critically important in this process because they emulsify the fal*, and form mixcd micelles. Solu-ble glycerol and short- and medium-chain fatty acids are absorbed without micelle łormation, pass through the epithelial cells, and are taken up in the portal circulation. The principal products of fat dig«.*v lion are fatty acids (absorbed coupled to Na'), monoglycerkles. and cholesterol. Further processing within the epithelial cells resuhs n d*-lomicron formation, and these chylomicrons are exocytosed altf-e basal membranę and taken up into lymphatic lacteals. They ente^ thoracic duet and are evcntually emptied into the venous system. Divalent cations in the lumen of the intestine can form insoluble orr?-plexes. preventing absorption. By this same mechanism, malabsarp-tion of fat can impair intestinal Ca²* absorption.