Pinocytosis
This is an amoeba like action of the epithelial cell membrane in which a food particle or a macromolecule is encompassed and thereby brought into the cell. It may account for occasional absorption of large molecules, such as those of a protein or a fat. It is unlikely that this mechanism plays an important role in the normal absorption of any nu trien t. However, pinocytosis is believed to be functioning during the later stages of fetal life and in the prenatal period, enabling nursing infants to absorb antibodies from breast milk. Similarly, artificially fed infants appear to absorb foreign antigens and antibodies from their feedings.Extrusion of these macromolecules from the epithelial cell employs the same process in reverse.
