[Vascular morphology of the bovine testis. Light and scanning electron microscopic studies].

The testicular artery of the bull-testis shows a straight course from the end of the pampiniform plexus to the caudal extremity of testis. There it branches off in Rami tunicales, which lie as stratum arteriosum superficially to the albugineal veins of testis: a multi-layered stratum venosum. Arterial Rami parenchymales centripetales run directly to the mediastinum testis, form coils and then divide in approximately 10 or more thinner Rami parenchymales centrifugales, which extend from the coils into the parenchyma of the gonad. The three-dimensional microvasculature of the bull-testis is strikingly different from that of rodents: The peritubular network of capillaries in the interstitial space is positioned in a more irregular way. Only here and there is discernible a rope-ladder-like or polygonal arrangement of capillaries. A subalbugineal plexus does not exist in the bovine testis. Parenchymal veins drain in albugineal veins and these empty in the venous networks of the pampiniform plexus. Valves are a rare finding in testicular veins. Already low perfusion-pressure easily forces the corrosion-compound to leave the capillary bed and form typical extravasations as bent shovel-like plates, thus filling the clefts of peritubular spaces. Arteries and veins are directly embedded in the parenchyma of testis, surrounded only by a relatively thin margin of perivascular connective tissue. There are no septula testis and therefore a lobular organisation of bovine testis does not exist. The angioarchitecture of the testis plays an important role in thermoregulatory and androgen-transfer mechanisms as well as in the transport of rete-fluid to the epididymis.