Figure 1. Sperm production and epididymal maturation.

A. Spermatogenesis. The five major germ cell types within the testis are shown in a tubule cross section, where they develop in intimate association with Sertoli cells. Spermatogonia committed to spermatogenesis undergo mitotic divisions to form spermatocytes, which in turn undergo meiosis to generate round spermatids. Throughout the spermiogenesis period, spermatids become dramatically remodelled from a round to an elongated shape and eventually are released from the Sertoli cell as sperm in a process known as spermiation. On the right hand side, the typical phenotypes expected for knocking out genes with clear roles in each respective germ cell type are shown. Azoo = azoospermia; terato = teratozoospermia; astheno = asthenozoospermia; oligo = oligozoospermoa; OAT = oligoasthenoteratozoospermia. Basement membrane – dark purple; Sertoli cell nucleus – light purple; peritubular myoid cells – green. B. Sperm are generated within the seminiferous tubules of the testis and then travel to the epididymis, wherein they undergo a complex process of epididymal maturation. Sperm enter the epididymis through initial section of the epididymis and travel through the caput and corpus, the major sites of epididymal maturation. They are then concentrated within the cauda, where they are stored in a quiescent state prior to ejaculation. However, they will only achieve full functional capacity after undergoing the process of capacitation whilst in the female reproductive tract.