Seminiferous tubules. Light micrograph (LM) of seminiferous tubules of the testes, showing spermatogenesis, the process by which mature sperm is produced. The seminiferous tubules are highly convoluted tubules about 200-300 microns in diameter. They are separated from the surrounding connective tissue by a basement membrane. The tubules contain the Sertoli cells, which form a framework for the support and nutrition of the cells involved in spermatogenesis. Several stages in the development of the sperm cells are visible here culminating in the spermatids (immature spermatozoas) with their tails projecting into the lumen (space) of the tubule.