Sperm production, called spermatogenesis, occurs in the seminiferous tubules. There are approximately 800 seminiferous tubules in each testis. Each tubule is slender, tightly coiled, and approximately 31.5 inches (80 centimeters) long. Each testis contains nearly half a mile of seminiferous tubules. Spermatogenic (sperm-forming) cells line the seminiferous tubules.