Spermatocytogenesis
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Spermatocytogenesis is the male form of gametocytogenesis and involves stem cells dividing to replace themselves and to produce a population of cells destined to become mature sperm. The stem cells involved are called
spermatogonia A spermatogonium (plural: ''spermatogonia'') is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testicles. There are three subtypes of spermatogonia in human ...
and are a specific type of stem cell known as gametogonia. Three functionally separate spermatogonia cell types are recognized on the basis of the appearance of the nuclei: ''type A dark spermatogonia'' (Ad), ''type A pale spermatogonia'' (Ap), and ''type B spermatogonia'' (B).


Type Ad spermatogonia ("dark")

The population of spermatogonia is maintained by ''type Ad spermatogonia''. These cells do not directly participate in producing sperm, instead serving to maintain the supply of stem cells for spermatogenesis. Each type Ad spermatogonium divides to produce another type Ad spermatogonium, which can further carry on spermatogenesis, and one ''type Ap spermatogonium'', which differentiates further.


Type Ap spermatogonia ("pale")

''Type Ap spermatogonia'' repeatedly divide mitotically to produce identical cell clones linked by cytoplasmic bridges (in rodents, not in primates such as humans). The connections between cells allow development to be synchronized. When repeated division ceases, the cells differentiate into ''type B spermatogonia''. This stage is referred to as the ''spermatogonia phase''.


Type B spermatogonia

''Type B spermatogonia'' undergo
mitosis Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identic ...
to produce diploid intermediate cells called primary spermatocytes.


References


See also

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Oogenesis Oogenesis () or ovogenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated before birth during embryonic devel ...
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Spermatogenesis Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testicle. This process starts with the Mitosis, mitotic division of the stem cells located close to the basement membrane of ...
{{Male reproductive system Mammal male reproductive system