testis /tes″tēz′/ pl. testes, one of the pair of male gonads that produces sperm and testosterone. The adult testes are suspended in the scrotum by the spermatic cords; in early fetal life they are contained in the abdominal cavity behind the peritoneum. Before birth they normally descend into the scrotum. The coverings of the testes are the skin and the dartos tunic of the scrotum, the external spermatic fascia, the cremasteric layer, the internal spermatic fascia, and the tunica vaginalis. Each testis is a laterally compressed oval body about 4 cm long and 2.5 cm wide that weighs about 12 g. It is positioned obliquely in the scrotum, with the cranial extremity directed ventrally and slightly laterally and the caudal end directed dorsally and slightly medially. The anterior border, lateral surfaces, and extremities of the organ are convex, free, smooth, and covered by the tunica vaginalis. The convoluted epididymis lying on the posterior border of the testis contains a tightly coiled tube that is about 20 feet long and connects with the vas deferens through which spermatozoa pass during ejaculation. Each testis consists of several hundred conical lobules containing the tiny coiled seminiferous tubules, each about 75 mm long, in which spermatozoa develop. In early life the tubules are pale in color, but in old age they become invested with yellow fatty matter. The tubules converge to form the rete testis, which is drained by the efferent ducts into the head of the epididymis. The testes are supplied with blood by the two internal spermatic arteries that arise from the aorta, are served by the testicular veins that form the pampiniform plexuses constituting the greater part of the spermatic cords, and are innervated by the spermatic plexuses of nerves from the celiac plexuses of the autonomic nervous system. Also called testicle. Compare ovary. See also scrotum. −testicular, adj.
