The vasa vasorum (VV) of explanted segments of the human great saphenous vein (Vena saphena magna; HGSV), harvested during dissection for coronary bypass grafts or diseased vein segments from the "Salzburger Landesklinikum," were studied by scanning electron microscopy and three-dimensional morphometry of microvascular corrosion casts. The main objective of this study was to examine the VV's structural arrangement in order to find the most vital segments of the HGSV and in turn to improve the results of coronary bypass surgeries. The study presents a meticulous analysis of the whole microvascular system of the VV of the HGSV and its three-dimensional arrangement. It is one of the first studies yielding detailed quantitative data on geometry of the VV of the HGSV. A detailed insight into different vascular parameters such as vessel diameter, interbranching, intervascular distances, and branching angles at different levels of the VV's angioarchitecture and in different parts of the HGSV in health and disease is given. Further, the geometry of bifurcations was examined in order to compute the physiological optimality principles of this delicate vascular system based on its construction, maintenance, and function.

"Vasa vasorum" derives from Latin and literally means "vessels of the vessels", which describes their function of providing blood and oxygen to the arteries and veins vessel's wall. They, in turn, supply blood and oxygen to the rest of the body [1]. Hence the Vasa vasorum are a system of small blood vessels which supply large blood vessels. In detail a network of small arterioles, venules and capillaries which supply the outer two layers of large blood vessels [2,3]. The largest blood vessels in the body (e.g. the human great saphenous vein, the aorta, etc.) depend on this supporting network to maintain their health and function. Thus, the Vasa vasorum are an important part of the blood circulatory system [3,4]. The structure of the Vasa vasorum varies first of all with the size as well as the function and location of the vessel. In the largest vessels it penetrates the tunica adventitia and the outer two third of the tunica media [5]. In smaller vessels the Vasa vasorum infiltrates only the adventitia. There are no Vasa vasorum in small vessels, because diffusion is sufficient for nourishment.The aim of this study is the examination of the Vasa vasorum of the human great saphenous vein (Vena saphena magna, HGSV) in normal and pathological (varicose) conditions. We try to explore the optimality principles (minimal lumen volume, minimal pumping power, minimal lumen surface, minimal endothelial shear force) which underlie the design of this Vasa vasorum. Using vascular corrosion casting (VCC), scanning electron microscopy (SEM) and 3D-morphometry (M3) we are able to calculate optimum vessel diameter and branching indices of arterial, capillary and venous bifurcations and thus vascular optimality.Another purpose of the study is the increase of knowledge of venous diseases, respectively to get an insight into the mechanism inducing varicogenesis. For these purposes we examined explanted segments of the HGSV which were taken during harvesting for coronary bypass grafts or varicose vein segments, from the University clinics for vascular and endovascular surgery, PMU Salzburg. The process of vascular corrosion casting starts with the dissection of the feeding artery from the surrounding tissue under a dissecting microscope, which is then cannulated with a glass cannula (gauge ~80µm).Prior to the injection of the methacrylic resin "Mercox-Cl-2B", the Vasa vasorum have to be rinsed with saline using an automatic infusion pump (flow rate is about 7ml/hr). After polymerisation the specimens are macerated with 7.5% potassium hydroxide in order to remove all organic material. Thereafter, the casts are rinsed with distilled water for several times and frozen in distilled water. The ice-embedded casts are freeze-dried and mounted on a stub using the "conductive bridge method" [5]. After sputtering with gold and examination under the scanning electron microscope (FEI/Philips XL-30 ESEM), 3D-morphometry (M3) is performed.Arterial feeders (Fig. 2) were found to approach the HGSV from nearby arteries every 15 mm forming a rich cap...

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

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