Testes make sperm and testosterone inside a cooled scrotal pouch
A testis is the male gonad, homologous to the ovary, charged with producing sperm and secreting androgens—chiefly testosterone. Two similar glands hang in the scrotum, an abdominal-wall extension; for about eighty-five percent of men the right hangs lower because of vascular anatomy.
Luteinizing hormone from the anterior pituitary drives testosterone release; follicle-stimulating hormone plus local testosterone steer spermatogenesis. Average adult dimensions approach five by two by three centimetres, with typical volumes near eighteen cubic centimetres within a fifteen-to-twenty-five range. The Tanner scale stages maturity from under one and a half cubic centimetres to over twenty. Larger volume correlates with more seminiferous tubules, Sertoli cells, and sperm output.
A tough tunica albuginea wraps coiled seminiferous tubules where germ cells mature from puberty onward into spermatozoa, then exit via rete testis and efferent ducts. Sertoli cells form the true epithelium and secrete inhibin to restrain FSH. Between tubules, Leydig cells manufacture testosterone that shapes puberty, secondary traits, libido, and even testicular size itself.
Blood arrives mainly via the testicular artery from the aorta, with collaterals from cremasteric and deferential arteries that can sustain the gland if the main vessel is tied. Lymph follows arteries to para-aortic nodes, unlike scrotal lymph to inguinal nodes. Sertoli tight junctions create a blood–testis barrier so late-appearing sperm antigens do not trigger autoimmunity—an abdominal developmental heritage still readable in cremaster muscle and covering layers.
Temperature explains why the organs sit outside the body at all. In 1926 Carl Richard Moore suggested that sperm production works best a little below core warmth, and the testes are indeed held near 34.4 °C, since anything above 36.7 °C hampers the process. The cremaster muscle acts as the thermostat, hoisting the glands closer when they need heat and letting them drop to shed it. Getting into position is a journey: about 97 percent of full-term boys, but only 70 percent of preterm ones, are born with both descended, and a lagging testis usually settles within six months. Torsion, by contrast, is an emergency; untwisting surgery within six hours saves roughly nine in ten.
Source: Testicle
