Figure 1.

Schematic of the mammalian testicular structure. The testis consists of two compartments: the ST and the interstitial space. The ST is surrounded by MPC, which together with Sertoli cells secrete substances to form the BL that encloses the seminiferous epithelium. The seminiferous epithelium is composed of different stages of developing germ cells, including SPG, PSCs, SSCs, RSs and ESs, which are surrounded by columnar Sertoli cells extending from the BL to the lumen of the seminiferous tubules. The BTB is formed by the junctions between neighboring Sertoli cells near the BL. BL, basal lamina; BTB, blood−testis barrier; ES, elongated spermatid; MPC, myoid peritubular cell; PSC, primary spermatocyte; RS, round spermatid; SPG, spermatogonia; SSC, secondary spermatocyte; ST, seminiferous tubule.