Physiology of intestinal absorption
Brazier, F.; Delcenserie, R.; Dupas, J.L.
La Revue du Praticien 51(9): 945-952
2001
ISSN/ISBN: 0035-2640 PMID: 11458607 Document Number: 535720
Hydrolysis of dietary constituents is necessary to allow nutrients absorption by the small intestinal enterocytes. The digestion process takes place in the intestinal lumen, in the brush border membrane, in the enterocyte, and is mediated by a large number of hydrolases secreted in the gastrointestinal tract or produced by the epithelial cells and localized in the brush border. Nutrients are essentially absorbed via a transcellular route across enterocyte cell membranes to enter bloodstream or lymphatic circulation. Transport of nutrients across apical or basolateral membranes occur by active or facilitated mechanisms involving specific transporters. Water, electrolytes and small molecules can be partly absorbed via paracellular pathway. Tight junction permeability is regulated by osmolarity of intercellular space, definite nutrient concentrations in lumen, and activity of brush border membrane transporters.