Answer: The testis consists of many coiled seminiferous tubules lined by germinal epithelium and Sertoli cells, with interstitial (Leydig) cells in between.
[Diagram: T.S. of testis showing several seminiferous tubules cut across, each with a basement membrane, spermatogonia at the periphery, primary and secondary spermatocytes and spermatids towards the lumen, Sertoli cells extending from base to lumen, sperms in the lumen; interstitial (Leydig) cells and blood capillaries in the connective tissue between the tubules; the whole covered by tunica albuginea.]
- Coverings: each testis is covered by an outer tunica vaginalis, a fibrous tunica albuginea and an inner vascular tunica vasculosa. Septa from the tunica albuginea divide the testis into about 200–300 testicular lobules.
- Seminiferous tubules: each lobule has 1–4 highly coiled seminiferous tubules, the sites of sperm formation. Each tubule is lined by a basement membrane and a stratified germinal epithelium.
- Germinal epithelium: consists of spermatogenic cells arranged in layers – spermatogonia (2n) near the basement membrane, then primary spermatocytes, secondary spermatocytes and spermatids, with spermatozoa lying in the lumen.
- Sertoli (sustentacular) cells: tall columnar cells extending from basement membrane to lumen. They nourish developing sperms, secrete inhibin and androgen-binding protein, and form the blood–testis barrier.
- Interstitial (Leydig) cells: polyhedral cells present in the connective tissue between the tubules, along with blood vessels. They secrete the male hormone testosterone under the influence of LH (ICSH).
- The tubules open into the rete testis, from which vasa efferentia lead the sperms to the epididymis.
