Illustration of the interior of a seminiferous tubule containing sperm cells within a testis (testicle). The seminiferous tubules are the site of spermatogenesis (sperm cell production). In spermatogenesis, stem cells called spermatogonia divide and differentiate, eventually forming spermatozoa (sperm). Sperm are the male gamete which carry one set of chromosomes and can fertilise the female gamete (oocyte).