Microvascularisation of the scrotal integument of Holstein-Friesian bulls.

Based on standard histological methods and specific injection technique, the study demonstrates for the first time the blood vessel system of the scrotal integument.The latter is relatively thin and shows a thick underlying fascia, the tunica dartos. The vessel networks found in both structures are somewhat different from each other, i.e., the former displays the typical integumental vessel scheme, which, because of its thinness, shows a higher vessel density. The tunica dartos displayed a blood vessel system with specific characteristics, i.e. horizontal networks are present, which are on the one hand directly connected to the rete dermidis and on the other hand, with the ascending (arteries) or descending (venes) vessels of the dartos, so that a rather uniform distribution and nutrition of the latter, including its muscle layers, is assured.The findings support the idea that the functions of the scrotal integument and the dartos are based on a dependable energy supply, but with regard to vessel type, particularly arteries, may also be involved in the regulation of blood flow. Thus, the scrotal integument as well as the dartos can be used for thermoregulation.