The testes or testicles are male sexual glands. The two testicles have an ovoid shape and measure 4 to 5 cm. Each testicle is divided into lobules containing the seminal ducts and Seritoli cells which produce spermatozoids. The seminal ducts lead to the epididyma from which arises the vas deferens. The spermatozoids in semen follow this duct to the seminal vesicles then the urethra. The testicles thus have an exocrine function (spermatogenesis) and an endocrine function (production of male hormones). At puberty, secretion of testosterone triggers the development of secondary male sexual characteristics.