There are three subtypes of spermatogonia in humans:
- Type A (dark) cells, with dark nuclei. These cells are reserve spermatogonial stem cells which do not usually undergo active mitosis.
- Type A (pale) cells, with pale nuclei. These are the spermatogonial stem cells that undergo active mitosis. These cells divide to produce Type B cells.
- Type B cells, which divide to give rise to primary spermatocytes.
- Schematic diagram of Spermatocytogenesis