Transmission electron micrograph of intestinal epithelium of rat in an advanced stage of fat absorption. Lipid droplets in intestinal epithelial cells are an exception to the general rule that intracellular lipid is not membrane bounded. In this case, the lipid is not destined for local use by the cells in which it resides. In the course of intestinal absorption of dietary fat, intralumenal fatty acids and monoglycerides diffuse through the plasma membrane of the brush border and are reesterified to triglyceride by enzymes in the membrane of the smooth end oplasmic reticulum. The small lipid droplets so formed are lodged within the lumen of the reticulum and not in the cytoplasmic matrix. After further processing in the Golgi complex, they are released into the intercellular clefts of the epithelium as chylomicrons, which continue their passage through the epithelium via a paracellular route.