MORPHOGENESIS OF THE CUTANEOUS VASCULATURE IN DOGS

The cutaneous vascular pattern in dog foetuses (Egyptian land race), ranging from 20 to 260 mm CVR length, was investigated. In foetuses of 20 to 60 mm CVR length, the blood vessels appeared in the form of irregular islets of primitive blood cellular elements. In foetuses of 70 to 80 mm CVR length, the Ramus arteriosum cutaneus pierced the dermis at various sites and branched successi vely. It was accompanied by the Ramus venosus cutaneus in a complete satellite pattern. In foetuses of 130 mm CVR length, the primary elements of Rete arteriosum dermidis could be demons trated at the thorax, belly, lateral surface of the thigh and back regions. The plexus venosus dermidis profundus surrounded Unit Vascular Zones at the back, belly, thorax, lateral surface of the thigh and forehead regions. The Plexus venosus subpapillaris pro fundus could be demonstrated at the thorax, lateral surface of the thigh and the forehead regions. The Rete capillare vaginae dermalis radicularis could be demonstrated as a simple retiform envelope around the inner portion of each hair follicle. At the forehead region, the Ramus arteriosum cutaneus was not accompanied
with the Ramus venosus cutaneus. In foetuses of 170 to 190 mm CVR length, the Plexus venosus subpapillaris profundus is oriented into a retiform manner at the thorax, back, belly and lateral surface of the thigh dividing the Unit Vascular Zone into several Subunit Vascular Zones. The Rete capillare papillae pili was recognized. In foetuses of 200 - 260 mm CVR length, the Rete arteriosum subpapillare became well differentiated and distributed centrally into the Subunit Vascular Zones at all the regions examined. Few valves could be demonstrated within the vessels of the Plexus venosus dermidis profundus at the belly and flank regions.