The primitive sex cords continue to proliferate and penetrate deep into the medulla to form the testis (medullary) cords and rete testis. Later these testis cords lose contact with the surface epithelium because of the formation of a dense connective tissue capsule around the testis, the tunica albuginea. The sex cords are composed of supporting Sertoli cells, derived from the mesothelium (coelomic epithelium) and spermatogonia, derived from the primordial germ cells. The interstitial Leydig cells are derived from the genital ridge mesenchyme. The primitive sex cord gives rise to the seminiferous tubules, rete testis (an anastomosing network of channels in the mesorchium) and tubuli recti. The efferent ductules derived from the remnants of the mesonephric tubules connect the rete testis to the derivatives of the mesonephric duct (epididimis, ductus defferens, seminal vesicle and ejaculatory duct).