The vasa vasorum of skeletonized and nonskeletonized segments of five human great saphenous veins (GSVs), harvested during coronary bypass grafting, were cannulated, rinsed, and injected (casted) with the polymerizing resin Mercox-Cl-2B. After removal of the dry vascular tissue, the casts were examined using scanning electron microscopy. Stereopaired images (tilt angle, 6°) were taken, imported into a 3D morphometry system, and the 3D architecture of the vasa vasorum (arterial and venous vasa as well as capillaries) was studied qualitatively and quantitatively in terms of vasa diameters, intervascular and interbranching distances, and branching angles. Diameters of parent (d 0 ) and large (d 1 ) and small (d 2 ) daughter vessels of arterial and venous bifurcations served to calculate asymmetry ratios (␣) and area ratios (␤). Additionally, deviations of bifurcations and branching angles from optimal branches were calculated for selected arterial vasa. The arrangement of the vasa vasorum closely followed the longitudinally oriented connective tissue fibers in the adventitia and the circularly arranged smooth muscle cell layers within the outer layers of the media. Venous vasa by far outnumbered arterial vasa. Vasa vasorum changed their course several times in acute angles and revealed numerous circular constrictions, kinks, and outpouchings. Due to their spatial arrangement, the vasa vasorum are prone to tolerate vessel wall distension generated by acute increases in blood pressure or stretching of the vessel without severe impact on vessel functions. Preliminary comparisons of data from the bifurcations of cast arterial vasa vasorum, with calculated optimal bifurcations, do not yet give clear insights into the optimality principle(s) governing the design of arterial vasa vasorum bifurcations of the human GSVs.

Objective: The detailed spatial arrangement of the vasa vasorum (VV) of the human great saphenous vein (HGSV) was demonstrated in qualitative and quantitative terms. Materials and Methods: Segments of the HGSV taken from cadavers 12–24 h post mortem and from patients undergoing aortocoronary bypassing were studied by light microscopy of India-ink-injected specimens and by scanning electron microscopy of vascular corrosion casts. Results: Arterial feeders were found to approach the HGSV from nearby arteries every 15 mm forming a rich capillary network within the adventitia and the outer two thirds of the media in normal HGSV, while in HGSV with intimal hyperplasia capillary meshes extended into the inner layers of the media. Within the media, capillary meshes ran circularly. Postcapillary venules drained centrifugally towards the adventitial venous vessels which finally formed venous drainers running adjacent to the arterial feeders. Three-dimensional morphometry of vascular corrosion casts of VV revealed that diameters of (i) arterial VV ranged from 11.6 to 36.6 µm, (ii) capillary VV from 4.7 to 11.6 µm and (iii) venous VV ranged from 11.6 to 200.3 µm. Conclusions: The 3D network of VV suggests these layers are metabolically highly active and therefore require a continuous blood supply. We conclude, therefore, that the VV network must be preserved during in situ bypassing.

The aim of the study was to describe and depict the spatial arrangement of the colon microcirculatory bed as a whole. Various parts of the large intestine and terminal ileum were harvested from either cadaver or section material or gained peroperatively. Samples were then injected with India ink or methylmetacrylate Mercox resin for microdissection and corrosion casting for scanning electron microscopy. The results showed that extramural vasa recta ramified to form the subserous plexus, some of them passing underneath the colon taeniae. Branches of both short and long vasa recta merged in the colon wall, pierced the muscular layer and spread out as the submucous plexus, which extended throughout the whole intestine without any interruption. The muscular layer received blood via both the centrifugal branches of the submucous plexus and the minor branches sent off by the subserous plexus. The mucosa was supplied by the mucous plexus, which sent capillaries into the walls of intestinal glands. The hexagonal arrangement of the intestinal glands reflected their vascular bed. All three presumptive critical points are only gross anatomical points of no physiological relevance in healthy individuals. Neither microscopic weak points nor regional differences were proven within the wall of the whole large intestine. The corrosion casts showed a huge density of capillaries under the mucosa of the large intestine. A regular hexagonal pattern of the vascular bed on the inner surface was revealed. No microvascular critical point proofs were confirmed and a correlation model to various pathological states was created.

The development of blood vessels during the first three postnatal weeks was studied in the ventral stripe of the spinotrapezius muscle of the rat by use of India ink-gelatine injections, and electron microscopy. The number of terminal arterioles and collecting venules remained unchanged postnatally in the observed area. A remarkable proximodistal gradient of vascular development was apparent: while the basic structure of the hilar vessels remained unchanged in the time studied, the intramuscular arteries and veins matured gradually. More peripherally, gradual maturation of terminal and precapillary arterioles was observed. The capillary endothelium and the pericytes showed immature features, and remained unchanged during the time studied. An intense rebuilding activity was found in the endothelial cells of the growing venules, expressed by various forms of gaps, covered by an intact basal lamina and pericytes. Numerous mast cells and macrophages were found along all vessels. Intramuscular lymphatics were not present prior to the first postnatal week.

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