Morphological studies on the vascular architecture in the boar spermatic cord.

The morphological features of the testicular artery and the pampiniform plexus in the boar spermatic cord were evaluated by light microscopy, corrosion cast technique combined with scanning electron microscopy and by transmission electron microscopy. The testicular veins could be subdivided into 4 types according to their perivascular elements and their location to the testicular artery. Type I vein consisted of large veins and gave rise to type II and III veins. Type II vein was composed of a single layer of veins and ran along the testicular artery, while type III vein consisted of several layers of veins and was located between type II veins. Type IV vein, which was regarded as a venous portal system, was composed of small muscular and pericytic venules and was located in the tunica adventitia of type II vein and the testicular artery. Occasionally, type IV vein penetrated deep into the tunica media of the testicular artery, accompanied by a fenestrated endothelium in its thin portion. The direct arterio-venous anastomosis between the pampiniform plexus and the testicular artery was not found. Type IV vein was considered to be the most important vessel in reducing the capacity of the barrier between the testicular artery and the veins (type II and III). It is, therefore, suggested that type IV venous network may play a role in transferring the substances between the artery and the veins.