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 testis.
There are three subtypes of spermatogonia in humans:
...
and are a specific type of stem cell known as
gametogonia.
Three functionally separate spermatogonial cell types are recognised 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
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
to produce identical cell clones linked by cytoplasmic bridges.
The connections between cells allow development to be synchronised. When repeated division ceases, the cells differentiate into ''type B spermatogonia''. This stage is referred to as the ''spermatogonial phase''.
Type B spermatogonia
''Type B spermatogonia'' undergo
mitosis
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
to produce diploid intermediate cells called
primary spermatocytes.
References
See also
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Oocytogenesis
Oogenesis, ovogenesis, or oögenesis 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 in the embryonic stage.
O ...
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Spermatogenesis
Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubule ...
{{Male reproductive system
Mammal male reproductive system