Question

Primordial germ cells form in the early mammalian embryo. For either
males or females, describe the events between the formation of the
primordial germ cells and their subsequent release as mature gametes.
What molecular factors are important during the early embryonic
stages, and how are hormones involved post-puberty?(500words)

Answer 1

First Germ cells differentiate into primordial germ cells, which move to gonads. After that, we get following procedure in males’ gametogenesis.

1. Development of the spermatogonial stem cell pool

During a strong hormonal signal, primordial germ cells give rise to gonocytes that move to the seminiferous tubules basement membrane. Here gonocytes divide into spermatogonial stem cells (SSCs) to maintain its initial pool in the testes. Afterward the spermatogenic cycle starts that comprises of divisons in spermatogonia, spermatocytes and spermatids. The SSCs divide into preleptotene primary spermatocytes accumulated in the seminiferous tubules. Now, spermatocytes divide into spermatogonia and leave the basement membrane. Spermatogonia are still present in the basement membrane of the seminiferous tubules.

2. The spermatogenic cycle

Afterward step of Spermatogenic lineage starts. The spermatogonia are primitive diploid germ cells and divide into three types of spermatogonia type A_single (A_s), A_paired (A_pr) and A_aligned (A_al). They divide until they fill the active stem cell pool.

3. Spermatogenesis

After that, the process of spermatogenesis starts. Spermatogia are diploid cells and divide into diploid primary sprematocytes, the process known as spermatocytogenesis. Then primary sprematocytes divide into haploid secondary sprematocytes. The secondary sprematocytes divide into haploid spermatids thorugh spermatidogenesis. Then maturation of spermatids occurs into functional spermatozoids and the process calls as through spermiogenesis spermiation. The mautre spermatozoids tranfer into epididymis hwere they get mature for motility and develop into sperms. This process calls as spermiation.

After puberty, three hormones play crucial roles; GnRH (gonadotropin-releasing hormone), luteinizing hormone LH and the follicle-stimulating hormone (FSH). These hormones work in both boy and girl. In boys, these hormones let the production of testosterone. In girls, these hormones start in the making of estrogen. However, LH and FSH later only work with girls after the production of testosterone and estrogen.