You are aware that gonads of the male are called testis. In man and other mammals testes are lodged in an integumentary pouch called the scrotum. It is an adaptation for regulating the internal temperature of the testis. Whereas in non-mammalian vertebrates testes are present inside the body cavity, the peritonium. Mammalian testis is made of a series of elongated follicles or seminiferous tubules. The lining of the tubules constitutes an epithelium from which the spermatozoa are proliferated.
Figure: Mammalian Testis
The interspaces between the seminiferous tubules are occupied by blood vessels, connective tissues, and the interstitial cells of Leydig. Seminiferous tubule is limited by a thin basement membrane, in an adult testis often all stages of spermatogenesis are found at any level in cross-section of the tubule.