Morphological and histometric study of human spermatogonia from birth to the onset of puberty.

Normal human testes obtained at autopsy from 99 male subjects whose ages ranged from a few days after birth to 13 years of age were studied by light and electron microscopy. Besides fetal and transitional spermatogonia, types Ap, Ad, and B spermatogonia, similar to those of the adult testis, are found. The number of spermatogonia per 10 cross sectioned tubules decreases slightly from birth (15.3 +/- 1.2) to 3 years of age (12.1 +/- 1.0), and increases afterwards until 8 years of age (28.2 +/- 2.6). After a brief decrease between the ages of 8 and 9, it increases markedly until 12-13 years of age (49.7 +/- 4.6). The number of fetal and transitional spermatogonia per 10 cross sectioned tubules is 5.3 +/- 0.5 at birth, and progressively decreases until they disappear at 6 years of age. The numbers of types Ap and Ad spermatogonia per 10 cross sectioned tubules are similar to one another from birth (about 5.2) to 12-13 years of age (about 21.5), except during the period between 4 and 10 years of age, when the number of type Ad spermatogonia slightly decreases with respect to that of type Ap. This period coincides with the appearance of type B spermatogonia, of which the number per 10 cross sectioned tubules progressively increases from 4 (0.2 +/- 0.02) to 12-13 years of age (6.7 +/- 0.5). All spermatogonial types are found either resting on the basal lamina or lying toward the lumen. Some of the basal spermatogonia, but mainly those occupying a more adluminal position, appear hypertrophic, bi- or trinucleated, or degenerated. These anomalous spermatogonia are more abundant at 3 and 8 years of age, prior to periods of spermatogonial proliferation. At these times spermatocytes and occasional spermatids are seen in some seminiferous tubules of some children.