Mammalian epididymis and its role in reproduction: A review

The epididymis is essential for sperm development and maturation, and subsequently, the ability of spermatozoa to penetrate and fertilize the female gamete. Functional differences in segments of the epididymis are reflected by histological differences among epididymal regions. The mammalian epididymis can be subdivided into a number of distinct regions: initial segment, intermediate zone, caput, corpus and cauda, depending upon the species. Proteins are secreted from epithelial cells in the mammalian epididymis by merocrine and apocrine secretion, although the functions of different epididymal proteins have not yet been determined. The significance of epididymal function for sperm maturation and male fertility has been highlighted recently in transgenic mice, where a primary defect in epididymal regionalization and differentiation caused by a dominant negative mutation of retinoic acid receptor aa (RAR) or disruption of c-ros tyrosine kinase receptor gene, leads to male infertility.