Structure of the germinal epithelium
The epithelium consists of Sertoli's sustentacular cells and the spermatogenic cells. The Sertoli's cells form a single-layered lamina and extend from the basal lamina to the tubule lumen. With their labyrinthine cellular processes they surround the individual types of germ cells more or less completely. Spermatogenesis is thus accomplished in close contact with the Sertoli's cells, which not only have supportive and nourishing functions, but also secrete hormones and phagocytize cell fragments. Somewhat above the basal lamina they are bound to each other through complicated occluding junctional complexes (tight junctions), so that 2 separated compartments are present in the epithelium: a basal one, in which the spermatogonia are lined up, and a luminal one, in which all the other stages of spermatogenesis are found.