Spermatogenesis

61 days

Spermatogenesis requires a temperature considerably lower than that of the interior of the body.

Ref: Ganong’s Review of Medical Physiology, 22nd Edition, Page 427; Guyton and Hall – Textbook of Medical Physiology, 10th Edition, Page 920

B i.e. Primary spermato cyte to secondary spermatocyte

A, B, & C i.e. Testosterone, FSH, & LH

Ans. is ‘b’ i.e., Seminiferous tubule

Spermatogenesis occurs in seminiferous tubules.

• Spermatogenesis refers to the process of formation of spermatozoa (sperm) from primitive germ cells (spermatogonia).
• Steps in spermatogenesis involve :‑

i) Spermatogonia (primitive germ cells) undergo mitosis to form primary spermatocytes. Both spermatogonia and primary spermatocytes have diploid chromosomes (46 chromosomes or diploid of 23 chromosomes).

ii) Primary spermatocytes undergo meiosis to form secondary spermatocytes. Secondary spermatocytes have haploid (23) chromosomes.

iii) Secondary spermatocytes undergo mitosis to form spermatids.

iv) Spermatids do not divide further but undergo morphological changes to form sperms (spermatozoa). This step of formation of spermatozoa from spermatids is called spermiogenesis. The spermiogenesis takes place in the deep folds of cytoplasm of sertoli cells.

Ans. is `b’ i.e., Early division of spermatogonia

Growth hormone specifically promotes early divisions of spermatogonia themselves. In the absence of GH, spermatogenesis is severely deficient or absent.

Growth hormone is also essential for general metabolic process in testis.

Hormones involved in spermatogenesis

 Spermatogenesis is influenced by many hormones. Hormones required for spermatogenesis are FSH, LH, testosterone, estrogen, growth hormones inhibin and activin.

FSH is responsible for initiation of spermatogenesis. It binds with sertoli cells and spermatogonia and induces the proliferation of spermatogonia. It stimulates certoli cells to secrete endrogen binding protein, inhibin, mullerian inhibing substance and estrogen.

LH stimulates leydig cells to secrete testosterone.

Testosterone is the principles hormone which directly stimulates spermatogenesis. It is responsible for the sequence of remaining stages of spermatogenesis (after initiatin by FSH). It is also responsible for maintenance of spermatogenesis.

Estrogen is formed from testosterone (by aromatase) in sertoli cells. It is essential for spermeogenesis (last step of spermatogenesis, i.e. formation of spermatozoa from spermatids).

Growth hormone is essentialy promotes early division of spermatogonia.

Inhibin plays an important role in regulation of spermatogenesis by feedback inhibition of FSH secretion.

Activin stimulates FSH secretion and stimulates spermatogenesis.