Spermatogenic function of the testis.

Spermatogenic function of the testis is discussed. The bulk of discussion is based heavily on data obtained from experiments on the rat. The basic structure and development of the testes are reviewed. The cycle of the seminiferous epithelium is defined and outlined. The mechanism responsible for germinal epithelium proliferation appears to be the principle of a self-renewing germinal stem cell. The stem-cell divisions result in formation of additional stem cells which remain dormant until the subsequent cycle and in the formation of Type A spermatogonia which enter the spermatogenic process and ultimately are transformed into mature spermatozoa. The kinetics of the spermatogenic process and the duration of spermatogenesis are discussed. The phagocytic activity of the Sertoli cells are discussed. Findings suggest that the Sertoli cell population in the adult testes is stable. However a lack of uniformity of distribution of Sertoli cells in the seminiferous tubules of human testis and marked variation in the absolute numbers of these cells in testes of different individuals have been reported.