The postnatal development of the human sertoli cells.

Seminiferous tubules from infant testes show a mean tubular diameter of 70 micron with a high number of Sertoli cells (20...24 cells) per transverse tubular section which form a pseudostratified epithelium. Basal Sertoli cells have round to ovoid nuclei, regular in outline, with small nucleoli. The cytoplasm contains the usual organelles homogeneously distributed. Columnar Sertoli cells reach the lumen and show basal projections which surround the basal Sertoli cells. Basal regions of columnar cells contain numerous parallel microfilaments. Apical regions contain abundant rough endoplasmic reticulum, several Golgi complexes, and associated vesicles of electrondense content, Desmosome-like structures and extensive, flattened interdigitations are observed between Sertoli cells. Gap junctions between peritubular myofibroblasts and Sertoli cells are occasionally seen. During childhood the seminiferous tubules show a similar pattern, but the number of Sertoli cells per transverse tubular sections decreases (16...19 cells). From 9 years of age onwards the seminiferous tubules become thicker, the number of Sertoli cells decreases (12...15 cells), and the pseudostratified epithelium is gradually replaced by a columnar epithelium. The Sertoli cells begin to mature and smooth endoplasmic reticulum, mitochondria and lipid droplets develop. Annulate lamellae, crystals of Charcot-Böttcher, and Sertoli-Sertoli specialized junctions appear.