Testis anatomy. Macro photoograph of a longitudinal section through an adult testis, part of the male reproductive system. The majority of the testis is taken up by seminiferous tubules (purple), which are arranged in lobes. The tubules are the site of sperm production (spermatogenesis). From the tubules the sperm move to the epididymis, which runs along the top of the seminiferous tubules here, where they are stored while they mature. Mature sperm travel along the vas deferens (brown, upper right) and are expelled from the urethra during ejaculation.