Testes and Epididymis - Anatomy & Physiology

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Vasculature

• The Testicular Artery a direct branch off the aorta.
  • This has important implications when performing castration procedures as the pressure within the artery will be very high and so it is imperitive to tie the artery off properly.
  • The testicular artery is highly convoluted and contains many elastic fibres within its wall. It acts as a pulse pressure eliminator between the inguinal ring and surface of the teste, minimising the differance between systolic and diastolic pressures within the artery (usually 40mmHg).
• The Pampiniform Plexus
  • The network of testicular veins that surround the testicular artery providing the testes with a countercurrent heat exchanger.
  • The testes require a temperature of 33°C in order for maintaining spermatogenesis, 3-6°C lower than core body temperature. This is achieved by the countercurrent exchange system between the pampiniform plexus and the testicular artery. Heat is transfered from the warmer blood in the testicular artery to the cooler blood returning from the testes in the testicular veins. The testicular veins run close to the surface of the scrotum so the blood within them is cooled by heat radiation from the skin of the scrotum.

Testicular Descent

The developing testes start off in the abdomen. They develop from somatic mesenchymal cells in the genital ridge found caudal to the developing kidneys, around the tenth thoracic vertebra. The testes migrate caudally and retroperitoneally towards the inguinal canal and scrotum. This translocation of the testis is the result of growth and contraction of the Gubernaculum aswell as the relative growth of associated viscera within the abdomen. The gubernaculum is a ligamentous structure extending from the site of the future scrotum, through the inguinal ring to the caudal testis. In the inguinal region the distal portion of the gubernaculum fuses with the covering peritoneum before its descent, forming the visceral and parietal vaginal tunics. These two layers of peritoneum cover the testes within the scrotum and are seperated by the vaginal cavity. Once the testes have descended into the scrotum the inguinal canal contracts behind them to keep them in place.