Testis

The testis, one of the male gonads, is a paired organ housed in the scrotum. Its position outside the body cavity helps maintain a temperature cooler than core body temperature, which is necessary for efficient spermatogenesis. Each testis is enclosed by a dense capsule called the tunica albuginea and a serous layer, the tunica vaginalis. Internally it contains lobules of seminiferous tubules where germ cells develop into sperm, supported by Sertoli cells, with interstitial Leydig cells between tubules that secrete testosterone.

Developmentally, the testes arise from the embryonic gonadal ridge and differentiate under the influence of the SRY gene. They descend from the abdomen into the scrotum during fetal development, guided by the gubernaculum. If descent is incomplete (cryptorchidism), fertility can be affected and cancer risk is increased.

The testes are supplied by the testicular arteries, branches of the abdominal aorta. Venous drainage forms the pampiniform plexus, which becomes the testicular veins; the left typically drains into the left renal vein and the right into the inferior vena cava. Innervation includes sympathetic and visceral afferents via the testicular plexus, with sensory fibers following the genital branch of the genitofemoral nerve. Lymphatic drainage mainly targets para-aortic (lumbar) nodes.

Functions include production of sperm through spermatogenesis and secretion of testosterone, which is essential for male development and reproductive function. Clinically important conditions involve testicular torsion, hydrocele, varicocele, and testicular tumors, particularly germ cell tumors such as seminomas and non-seminomatous tumors. Early recognition and management of testicular abnormalities are important for fertility and health.