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.
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.
This type is capable of dividing to produce either two identical type Ad spermatogonia or two type Ap spermatogonia. type Ad spermatogonia do not directly participate in producing sperm and simply ensure a supply of stem cells to participate in spermatogenesis is maintained.
Type Ap spermatogonia ("pale")
The connections between cells allow development to be synchronised. When repeated division ceases, the cells differentiate into type B spermatagonia. This stage is referred to as the spermatogonial phase.
Type B spermatagonia
Type B spermatagonia undergo mitosis to produce diploid intermediate cells called primary spermatocytes.