Describe the histology of 'human testis'. Write a note on human sperm.

Explanation

(a) Testis is externally covered by fibrous connective tissue called tunica albuginea.
(b) It is covered internally by tunica vascularis formed by capillaries and externally by an incomplete peritoneal covering called tunica vaginalis.
(c) Seminiferous tubules are lined by cuboidal germinal epithelial cells. The germ cells undergo the process of spermatogenesis.
(d ) T .S. of testis shows different stages of spermato- genesis like spermatogonia, primary and secondary spermatocytes, spermatids and sperms.
(e) Large pyramid cells present interrupted between germinal epithelium are sertoli cells.
(f) Sertoli cells provide nourishment to the sperms till maturation.
(g) Leydig cells present between seminiferous tubules secrete hormone testosterone after puberty.

It is microscopic, elongated haploid motile male gamete or paternal gamete measuring about `0 cdot 055 mm (60 mu m)` in length. Sperm remains viable for 72 hours, but can fertilize the ovum in-first 12 to 14 hours only.
(a) Head : It is flat and oval region consisting of a large nucleus and an acrosome. Acrosome secretes hydrolytic enzymes like hyaluronidase which helps in penetration of the egg during fertilization. The acrosome and anterior half of nucleus is covered by a fibrillar sheath.
(b) Neck : Short region having two centrioles proximal centriole plays a role in I cleavage of zygote. The distal centriole gives rise to the axial filament of the sperm.
(c) Middle piece : It serves as power house for sperm. It has many mitochondria that provides energy for movement of sperm.
(d) Tail : Long, slender and tapering structure formed of cytoplasm. It helps in movement of sperm.