Fig. 1.

Cellular composition of seminiferous tubules. A portion of a seminiferous tubule is shown in Upper. The most immature germ cells (spermatogonia) are located at the periphery, close to the tubular wall (W). Postmeiotic spermatids and maturing spermatozoa are concentrated in the lumen (L). The area in the large rectangle is enlarged in Lower. Note the differences in nuclear size and granularity of the chromatin between premeiotic (P) and meiotic (M) cells. Nuclei from both of these cell types can also be readily distinguished from the small, elongated, homogenously staining nuclei of postmeiotic spermatids and maturing spermatozoa, examples of which are shown within circles. In addition to germ cells, seminiferous tubules contain Sertoli cells, examples of which are shown within the small square. (Magnification: Upper, ×10; Lower, ×20.)