Gonads

Both gonads double as reproductive organs and endocrine glands. In males, a pair of testes sit in the scrotal sac and are built from two functionally distinct components: the seminiferous tubules, which produce sperm, and the interstitial (Leydig) cells lying between them, which secrete the male sex hormones collectively called androgens, chiefly testosterone. Under the combined influence of FSH and LH, testosterone drives maturation of the male reproductive organs, the appearance of secondary sexual characters (facial and axillary hair growth, muscular development, a deepened voice, and typically masculine behaviour), an increase in total bone matrix, and it plays a direct stimulating role in spermatogenesis itself. …