The junctional specializations of sertoli cells in the seminiferous epithelium

Attention is directed to an unusual type of junctional complex between Sertoli cells in the seminiferous epithelium. The space between the membranes of adjoining cells is narrowed to 70–90 Å over large areas of their contact surfaces. In the superficial cytoplasm of each cell is an extensive cisterna of the endoplasmic reticulum, parallel to the membrane and 400–600 Å from it. Spaced at more or less regular intervals in the thin layer of cytoplasm between the cisterna and the cell membrane are periodic densities that appear to be band‐like aggregations of fine filaments. The sub‐surface cisternae are smooth‐contoured on the side toward the cell membrane but bear ribosomes on the side facing the cytoplasm. The possible significance of these distinctive junctions is discussed in relation to the support of the germ cells and the coordination of the developmental events in the cycle of the seminiferous epithelium.