Spermatogenesis is a process of developing male gametes, known as sperm within the male reproductive organs, the testes. In this process, each sperm containing a single copy of each chromosome. To create the haploid gamete, a cell undergoes the process of meiosis in which the genome is replicated and divided twice to produce four haploid gametes. The process starts in the bottom part of seminiferous tubes and, progressively, cells go deeper into tubes and moving along them until mature spermatozoa reach the lumen, where mature spermatozoa are deposited. The division happens asynchronically; if the tube is cut transversally one could observe different maturation states. A group of cells with different maturation states that are being generated at the same time is called a spermatogenic wave.
It produces mature male gametes, commonly called sperm but more specifically known as spermatozoa, which can fertilize the counterpart female gamete, the oocyte, during conception to produce a single-celled individual known as a zygote. This is the cornerstone of sexual reproduction and involves the two gametes both contributing half the normal set of chromosomes to result in a chromosomally normal zygote.
To preserve the number of chromosomes in the offspring, which differs between species – one of each gamete must have half the usual number of chromosomes present in other body cells. Otherwise, the offspring will have twice the normal number of chromosomes, and serious abnormalities may result. In humans, chromosomal abnormalities arising from incorrect spermatogenesis result in congenital defects and abnormal birth defects, and in most cases, spontaneous abortion of the developing fetus.
Process of Spermatogenesis
It is a process of gametogenesis in males. In females, oogenesis occurs to form a mature ovum.
- The male germinal cells or spermatogonia present in seminiferous tubules undergo proliferation by mitotic division.
- Some of the spermatogonia cells undergo meiotic division and are known as Primary spermatocytes (diploid, 2n=46).
- Secondary spermatocytes (haploid, n=23) are formed after the first meiotic division of primary spermatocytes.
- Secondary spermatocytes undergo a second meiotic division forming four haploid spermatids.
- Spermiogenesis- the transformation of spermatids to mature sperms or spermatozoa.
- Spermiation- The end of the process, the release of mature sperms from seminiferous tubules.