Ventral view

The epididymis is an accessory sex organ.  It has embryological origins from the Wolffian duct.  It is found posterior to the testis.  At the superior end is the broad end called the head, followed inferiorly by the body and then the tail.  The vas efferens enters the head of the epididymis and empties into the duct of the epididymis.  The coiled tubes that make up the epididymis are about 20 feet long!  Surrounding the tube is connective tissue. The tube emerges as the vas deferens from the tail of the epididymis and begins its course toward the spermatic cord and the external inguinal ring.  The length of the tube is important as a storage place for spermatozoa, and it is in this tube that they mature, which includes the development of a flagellum.  The spermatozoa spend about 20 days in the duct of the epididymis.  The epididymis duct is important in absorbing testicular fluids and may add substances to nourish the spermatozoa.  Smooth muscles in the walls of the epididymis contract during ejaculation causing the spermatozoa to move into the vas deferens.  If there is no ejaculation, the spermatozoa stay there for up to several months after which they are phagocytized by the epithelial cells in the duct.