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BLOOD SUPPLY OF THE TESTIS


BLOOD SUPPLY OF THE TESTIS
The arterial supply to the testis is derived from three sources: the internal spermatic artery, the deferential (vasal) artery, and the external spermatic or cremasteric artery. The internal spermatic artery originates from the abdominal aorta just below the renal artery. Embryologically, the testicles lie opposite the second lumbar vertebra and keep the blood supply acquired during fetal life. The internal spermatic artery joins the spermatic cord above the internal inguinal ring and pursues a course adjacent to the pampiniform venous plexus to the mediastinum of the testicle. The vascular arrangement within the pampiniform plexus, with the counter-flowing artery and veins, facilitates the exchange of heat and small molecules. For example, testosterone passively diffuses from the veins to the artery in a concentration-limited manner, and a loss of the temperature differential created by this system is associated with testicular dysfunction in men with varicocele and cryptorchidism.

Near the mediastinal testis, the internal spermatic artery is highly coiled and branches before entering the testis. Extensive interconnections between the internal spermatic and deferential arteries allow maintenance of testis viability even after division of the internal spermatic artery. The testicular arteries penetrate the tunica albuginea and travel inferiorly along the posterior surface of the testis within the parenchyma. Branching arteries pass anteriorly over the testicular parenchyma. Individual arteries to the seminiferous tubules, termed centrifugal arteries, travel within the septa that contain tubules. Centrifugal artery branches give rise to arterioles that supply individual intertubular and peritubular capillaries.
BLOOD SUPPLY OF THE TESTIS

The deferential artery (artery of the vas) may originate from either the inferior or superior vesical artery (see Plate 2-6) and supplies the vas deferens and the cauda epididymis. A third artery, the external spermatic or cremasteric artery, arises from the inferior epigastric artery inside the internal inguinal ring, where it enters the spermatic cord. This artery forms a network over the tunica vaginalis and usually anastomoses with other arteries at the testicular mediastinum.
Veins within the testis are unusual in that they do not run with the corresponding intratesticular arteries. Small parenchymal veins empty into either the veins on the testis surface or into a group of veins near the mediastinum testis. These two sets of veins join with deferential veins to form the pampiniform plexus. The pampiniform plexus consists of branches of freely anastomosing veins from (1) the anterior (or internal) spermatic veins that emerge from the testicle and accompany the spermatic artery to enter the vena cava; (2) the middle deferential group that accompanies the vas deferens to pelvic veins; and (3) the posterior or external spermatic group that follows a course along the posterior spermatic cord. The latter group empties into branches of the superficial and deep inferior epigastric veins and the superficial and deep pudendal veins. The middle and posterior veins provide collateral venous return of blood from the testicles after internal spermatic vein ligation with varicocelectomy.
The right internal spermatic vein enters the inferior vena cava obliquely below the right renal vein forming a natural “valve” to reduce retrograde blood flow, whereas the left vein terminates in the left renal vein at right angles, without a natural valve. This anatomic relationship is thought to explain the fact that 90% of varicoceles are on the left side.
With varicocele formation, the blood flow in the internal spermatic vein is reversed, thus disturbing venous drainage from the testis and potentially elevating scrotal temperature. As a consequence, orchalgia and infertility can occur. In high-ligation varicocelectomy procedures (Palomo), the internal spermatic artery and vein are both ligated above where the deferential vessels and the external spermatic veins exit the spermatic cord, thus affording sufficient collateral circulation to maintain testis viability. During inguinal or subinguinal procedures, care is needed to spare the internal spermatic artery, as collateralization may be less extensive at this anatomic level.