Anatomy of Testis

Structure of the Testis

• The testis is surrounded by a dense connective tissue capsule called the tunica albuginea, which thickens on the posterior side to form the mediastinum testis.
• The mediastinum testis is a fibrous region that penetrates the organ and divides it into approximately 250 pyramidal compartments or testicular lobules.
• Each lobule contains sparse connective tissue with endocrine interstitial cells (Leydig cells) that secrete testosterone, and one to four highly convoluted seminiferous tubules where sperm production occurs.

Development and Location of the Testes

• The testes develop retroperitoneally in the dorsal wall of the embryonic abdominal cavity.
• During fetal development, the testes are moved to become suspended in the two halves of the scrotal sac, or scrotum, at the ends of the spermatic cords.
• Each testis carries with it a serous sac, the tunica vaginalis, derived from the peritoneum, which consists of an outer parietal layer lining the scrotum and an inner visceral layer covering the tunica albuginea.

Temperature Regulation in the Scrotum

• The process of sperm formation requires a permissive temperature of about 34°C, which is maintained in the scrotal sac by various mechanisms.
• The testicular artery is surrounded by a rich pampiniform venous plexus containing cooler blood from the testis, which draws heat from the arterial blood by a countercurrent heat-exchange system.
• Evaporation of sweat from the scrotum also contributes to heat loss.
• The dartos muscle of the scrotum and the cremaster muscles of the spermatic cords allow for further control on testicular temperature by moving the testes away from or closer to the body.