SCANNING ELECTRON MICROSCOPE OBSERVATION OF PENILE VASCULAR CASTS IN THE DOG: AN INQUIRY INTO THE POSSIBLE MECHANISM OF ERECTION BASED ON THE FINDINGS

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Abstract
The vascular construction of the dog penis was investigated mainly by scanning electron microscopic observation of corrosion casts produced by injection of methylmethacrylate into the penile artery and its branches. The corpus cavernosum penis was supplied mainly by the penile deep artery; only its distal end received a few small branches from the dorsal artery. The helicine arteries were provided with polsters which protruded into the lumen so prominently that they might conspicuously reduce the luminal space during the flaccid state of the penis. The polsters were restricted to the helicine arteries, and could not be found in the penile deep artery or in veins of the penis. Cavernous sinuses strikingly anastomosed each other forming a vascular network as a whole. No connection of sinuses was present between the corpus cavernosum penis of either side. Postcavernous venules in the corpus cavernosum penis occurred only on its dorso-medial surface at the point where the crus penis of either side converged; a well-developed capillary network was found in the same region. The postcavernous venules ran for a distance beneath the tunica albuginea, and it is apparent that they are effectively compressed between the tunica albuginea and the peripheral sinuses during erection. In contrast, the cavernous sinuses in the corpus spongiosum urethrae directly emptied into a vein penetrating the thin tunica albuginea. The drainage vein with large calibers was unlikely to receive significant mechanical compression during erection. No arterio-venous anastomoses could be found either within or out of the cavernous bodies.