Illustration showing the interior of a testis (oval), the epididymis (c-shape right of testis) and the vas deferens, or sperm duct (ascending tube). These are three organs within the male reproductive system which are involved in sperm production (spermatogenesis) and transport. Sperm cells are produced via meiosis in the seminiferous tubules (coiled tubes within testis). Mature sperm cells (spermatozoa) migrate to the epididymis, where they are stored until sexual stimulation. Upon stimulation, muscle in the vas deferens wall reflexively propels spermatozoa towards the urethra.