The epithelium of the female reproductive tract undergoes cyclic morphologic alterations in cell shape, apical microvilli, ciliation, and secretion. These changes are hormone-dependent. The endometrial fluid is made of (a) components from the transudation of the blood serum and (b) protein, carbohydrate and other metabolites synthesized within the endometrial cells and discharged through the apical cell membrane. Endometrial cells have several mechanisms of transport processes across the plasma membrane. These processes regulate cellular volume, nutrition, excretion and communication along the surface of the cell as well as the intra-cellular and extracellular communication. The endometrial secretions play a major role in the capacitation of spermatozoa, and the nutrition of the blastocyst.