Question

Write a note on: Spermatogenesis.

Answer 1

Detailed information on the arrangement of the germinal epithelium, the structure and function of various types of germ cells, endocrine and paracrine cells and mechanisms, and the intratesticular and extratesticular control of spermatogenesis is needed to understand spermatogenesis.

Complete answer:
The origin and development of the sperm cells inside the male reproductive organs, the testes, is spermatogenesis. The testes consist of several small, tightly coiled tubules known as seminiferous tubules; inside the walls of the tubules, the sperm cells are formed.

There are also several randomly scattered cells within the walls of the tubules, called Sertoli cells, that work to support and nourish immature sperm cells by providing them with nutrients and blood products. The Sertoli cells help to transport them from the outer surface of the seminiferous tubule to the central channel of the tubule as the young germ cells expand.

The testicles develop sperm cells constantly, although not all parts of the seminiferous tubules develop sperm cells at the same time. To attain final maturation, one immature germ cell takes as long as 74 days, and there are irregular resting periods during this development period.

Immature cells in the outer wall of the seminiferous tubules (or spermatogonia) are all derived from cells called stem cells. Stem cells are nearly exclusively composed of radioactive material. By multiplying in the cell replication phase known as mitosis, the stem cells begin their phase.
Half of this original crop's new cells continue to become potential sperm cells, while the other half serve as stem cells, so that more germ cells are continuously supplied.

As primary sperm cells, spermatogonia expected to grow into mature sperm cells are known. These transfer to a more central position from the outer portion of the seminiferous tubule and connect themselves around the Sertoli cells. By raising the amount of cytoplasm and structures called organelles inside the cytoplasm, the primary sperm cells then grow more. The primary cells differentiate into a shape called a secondary sperm cell after a resting period.

A splitting of the genetic content occurs during this cell division. There are 46 chromosomes in the nucleus of the main sperm cells; only 23 chromosomes are found in each of the secondary sperm cells, as they are in the egg. The traits of both entities blend and the new organism continues to evolve as the egg and sperm merge and their chromosomes join.

Before it can fertilise an egg, the secondary sperm cell also needs to mature; maturation requires some modifications in the sperm cell's shape and structure. The nuclear content becomes more compact and oval in form; as the head of the sperm, this region grows. A cap called the acrosome, which is important in helping the sperm gain entrance into the cell, partly covers the head. Attached to the head's opposite end is the tailpiece. The tail is derived from the cytoplasm of a secondary sperm cell. It consists of a long, slender bundle of filaments in the mature sperm that propel the sperm through its undulating movement. It is transferred through the long seminiferous tubules until the sperm has matured and deposited in the epididymis of the testicles until it is able to leave the male body.

Note: At all stages, the replication and development of male germ cells and the intratesticular and extratesticular spermatogenesis control processes may be disrupted. This can arise as a result of environmental factors or may be attributed to diseases that affect spermatogenesis directly or indirectly.
In addition, spermatogenesis may be reduced or damaged by various nutritional substances, therapeutics, medicines, hormones and their metabolites, various radioactive substances or by x-radiation.