Answer:
[Figure: T.S. of testis — outer tunica albuginea; several seminiferous tubules in section, each with a basement membrane, germinal epithelium showing spermatogonia, primary and secondary spermatocytes, spermatids and sperms towards the lumen, and Sertoli cells; groups of interstitial (Leydig) cells and blood vessels in the spaces between the tubules.]
- Coverings: each testis is covered by three layers — outer tunica vaginalis, middle fibrous tunica albuginea and inner tunica vasculosa (vascular). Septa from the tunica albuginea divide the testis into about 200–300 testicular lobules.
- Seminiferous tubules: each lobule contains 1–4 highly coiled seminiferous tubules. Each tubule is lined by germinal epithelium resting on a basement membrane. It contains:
- spermatogenic cells (spermatogonia, primary and secondary spermatocytes, spermatids) which by spermatogenesis form sperms that are released into the lumen;
- Sertoli (sustentacular) cells, tall cells that provide nourishment to developing sperms, secrete inhibin and form the blood–testis barrier.
- Interstitial (Leydig) cells: present in the connective tissue between the seminiferous tubules along with blood vessels; they secrete the male hormone testosterone (androgens).
- The tubules open into the rete testis, from which vasa efferentia carry sperms to the epididymis.
