Seminiferous tubules. Coloured Scanning Electron Micrograph (SEM) of sectioned seminiferous tubules the site of sperm production in the human testis. Each tubule contains a swirl of forming sperm cells (red). Testes are packed with seminiferous tubules. The tubules are lined by a stratified epithelium containing two types of cell: Sertoli cells, which nourish developing sperm, and spermatogenic cells, which produce the sperm. The sperm are released into the cavity of the tubule to migrate to the epididymis, where they mature. Around the seminiferous tubule are Leydig cells (green) which produce testosterone. Magnification: x72 at 6x7cm size.