Spermatogenesis, the basic and development of the sperm cells in the male reproductive organs, also known as the testes. The testes are made up of numerous thin, tightly coiled tubules called seminiferous tubules; the sperm cells are formed in the walls of the tubules. Within the walls of the tubules, also, are many randomly scattered cells, called Sertolicells that function to support and nourish the immature sperm cells by giving them nutrients and blood products. As the young germ cells grow, the Sertoli cells help to transport them from the outer surface of the seminiferous tubule to the central channel of the tubule.

Sperm cells are continually being produced by the testes, but not all areas of the seminiferous tubules produce sperm cells at the same time. One immature germ cell takes as long as 74 days to reach final maturation, and during this growth process there are intermittent resting phases.

The immature cells are all obtained from cells known as stem cells in the outer wall of the seminiferous tubules. The stem cells are entirely made up of nuclear material. (The nucleus of the cell is the portion containing the chromosomes.) The stem cells begin their process by multiplying in the process of cell duplication known as mitosis. Half of the new cells go on to become the future sperm cells from this initial crop, and the other half remain as stem cells so that there is a constant source of additional germ cells. Spermatogonia that are going to develop into mature sperm cells are called primary sperm cells. These move from the outer portion of the seminiferous tubule to a more central location and attach themselves around the Sertoli cells. The primary sperm cells then develop somewhat by increasing the amount of cytoplasm (substances outside of the nucleus) and structures called organelles within the cytoplasm.The primary cells divide into secondary sperm cell after ta resting phase.in course of this cell division there is a split up of the nuclear material. In the nucleus of the primary sperm cells there are 46 chromosomes; every secondary sperm cell contain only 23 chromosomes, as there are in the egg. When the egg and sperm combine and their chromosomes unite, the characteristics of both individuals blend and the new organism starts to grow.

The nuclear material becomes more condensed and oval in shape; this area develops as the head of the sperm. The head is covered partially by a cap, called the acrosome, which is important in helping the sperm to gain entry into the egg. Attached to the opposite end of the head is the tailpiece. Once the sperm has matured, it is transported through the long seminiferous tubules and stored in the epididymis of the testes until it is ready to leave the male body.


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