Vasa vasorum of blood and lymph vessels in the broad ligament of the sheep uterus analyzed by scanning electron microscopy.

The morphology of vasa vasorum of the blood and lymph vessels in the broad ligament of the uterus was examined in 12 adult ewes. The technique of vascular corrosion casts with the usage of Mercox resin allows multiple surveys of a three-dimensional organization of vascular networks under a scanning electron microscope (SEM). The study was appended by tissue pieces dried by the critical point method for SEM and semi-thin sections stained with toluidyne blue for light microscopy. Vasa vasorum surrounded both the larger vessels and the lymph vessels emanating from the ovary and the uterus. Significant differences in location and intensity of vasa vasorum in blood vessels were observed. They were less developed in the first part of the ovarian and the uterine arteries than in their smaller branches. Significantly large, two- or even three-layer vasa vasorum surrounded the ovarian and the uterine branches of the ovarian artery as well as the ovarian veins in the area of mesovarium. In the other areas of the broad ligament of the uterus, arterial vessels of similar sizes usually had a single-layer vasa vasorum. The lymph vessels leaving the ovary and uterus were surrounded by dense, although usually single-layed, microvascular network. The presence of vasa vasorum on relatively small blood and lymph vessels of the broad ligament of uterus indicates their particular functions that are probably connected with the estrous cycle or pregnancy and changes of blood flow rate entering the ovary and uterus. However, the presence of significantly developed, multi-layer vasa vasorum networks on only some of the blood vessels indicates that it is probably one of the vessels morphological adaptations to serve the counter-current transfer of biologically-active regulators in the area of the broad ligament of the sheep's uterus.