Question

Give the schematic representation of spermatogenesis.

Answer 1

The process that leads to the formation of male gametes is called spermatogenesis. This process begins with the mitotic division of the stem cells situated near the basement membrane of the tubules. These cells are known as spermatogonial stem cells. Spermatogenesis occurs in the seminiferous tubule which is present inside the testes.

Complete answer:
Spermatogenesis creates mature male gametes, commonly termed sperm, which are capable of fertilizing the counterpart female gamete, the oocyte, during fertilization to produce a single-celled organism known as a zygote. The entire process of spermatogenesis can be broken up into several distinct stages based on a particular type of cells formed during the stage in humans.

1. This process begins with the mitotic division of the spermatogonial stem cells located close to the basement membrane of the tubules. The mitotic division of these produces two types of cells: one replenishes the stem cells and others that differentiate into primary spermatocytes.
2. The primary spermatocyte divides meiotically into two secondary spermatocytes, this is called meiosis I.
3. Each secondary spermatocyte splits into two equal haploid spermatids by Meiosis II.
4. Spermatids mature into full-fledged spermatozoa, also known as sperm cells.
   Thus, the spermatogonial stem cell divides into replenishing cell and primary spermatocyte, the primary spermatocyte gives rise to two secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa and four haploid cells. Hence each cycle of spermatogenesis gives four haploid sperms.

Note:
Hormones controlling spermatogenesis vary among species. In humans the mechanism is not completely known; however, it is identified that initiation of spermatogenesis happens at puberty due to the interplay of the hypothalamus, pituitary gland, and leydig cells.