Also found in: Dictionary, Medical, Wikipedia.
a developing male sexual cell during the period of division prior to growth. Spermatogonia are in a state of rapid mitotic division. Primary and secondary spermatogonia are distinguished in insects and certain other invertebrates; secondary spermatogonia, the smaller of the two types, are surrounded by cells that form the seminal vesicle, or spermatocyst. Mammals have two types of spermatogonia, which differ in degree of differentiation and in chromatinic structure. The duration of the period of division varies from one animal species to another, depending on the number of generations and the rate of division of spermatogonia—parameters that are constant for eachspecies. Spermatogonia are formed in the parietal layer of the seminiferous tubules. Many animals have a specific zone of division in the cecum of the testes.