How are epithelial cells adapted for absorption? (and where are they found?)

(vili are the tiny projections that cover each fold of the ileum) Each epithelial cell covering the villus attached to surrounding cells to form tight junctions. This allows most materials to pass into the blood vessels that line the villi. The cell surface membrane on the intestinal lumen side has extensions called microvilli. The collection of microvilli on the intestinal side of the epithelial cells is called the brush border. The function of the brush border is to increase the surface area for absorption. Relatively high amounts of ATP are required to drive active transport processes. Thus epithelial cells have large numbers of mitochondria. Pinocytic vesicles are often present in large numbers due to absorption of some foods by endocytosis. The surface facing the lumen of the intestine is referred to as the apical surface and the surface facing the blood vessels is referred to as the basal surface. These surfaces have different types of proteins involved in material transport.