Although the epididymides are continuous with and in contact with the testis, they are separate organs. The epididymides are elongated structures that lie on the outer surfaces of the testes. The epididymis is the organ that supports sperm maturation and storage.
The epididymis has three regions:
Head - the proximal portion of the epididymis consists of about 12 efferent ductules that conducts sperm from the rete testis into a common duct.
Body - the central portion of the epididymis, consisting of a single, muscular duct filled with maturing sperm.
Tail - the distal segment of the epididymis is merely an extension of the duct found in the body of the epididymis. Sperm that leave the body during ejaculation originated from the tail of the epididymis.
Figure 1: A labeled illustration of a sagittal view of the epididymis.
Sperm are nourished within the epididymis to become mature and motile cells. The epididymis also stores sperm cells. Sperm are destined to stay within the epididymis until they leave during ejaculation. Sperm that remain in the epididymis for longer than a few months die and are reabsorbed by the cells of the epididymis.