This image shows a cross section taken through the testis.  The testis is covered by a dense fibrous connective tissue layer called the tunica albuginea.  Fibrous invaginations of the tunica albuginea divide the testis into 200 to 300 internal compartments called lobules.  Each lobule contains several highly coiled seminiferous tubules which are the sites of sperm production (spermatogenesis). As the sperm mature, they move from the seminiferous tubules into a network of ducts called the rete testis.  From the rete testis sperm move into the epididymis.  The spaces between adjacent tubules contain many small interstitial cells (Leydig cells). These cells secrete the male sex hormone, testosterone.