Epididymis

Fully formed spermatozoa released from the seminiferous tubules pass through the rete testis into the epididymis. The epididymides are the major sites of storage of spermatozoa, and most spermatozoa are contained in the tail of each epididymis.

Spermatozoa entering the head of the epi­didymis from the rete testis are immotile and incapable of fertilization. During their passage through the epididymis, spermatozoa acquire motility and become capable of fertilization. Presumably, these two characteristics are closely linked. The functional changes in spermatozoa that occur during their passage through the epididymis depend in part on epididymal secre­tions and testosterone in the epididymal fluids. Some minor morphologic changes (e.g., changes in nuclear chromatin and the acrosome) may also occur during the passage through the epididymis.