What are the functions performed by the testis in human beings?

Testes are the primary sex organs of a male reproductive system that lie outside the abdominal cavity in the scrotal sac. Each testis is divided into lobules by connective tissue and each lobule contains one to three seminiferous tubules which are the site for sperm formation. The large sustentacular cells that extend from the capsule to the lumen of the seminiferous tubule are called as Sertoli cells. They serve to support, nourish and regulate the development of cells undergoing spermatogenesis. The endocrine cells present in the space between seminiferous tubules are termed as interstitial cells or interstitial cells of Leydig. They serve to secrete androgen, testosterone, which is responsible for the development of male secondary sexual characters.