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Three-dimensional architecture of the microvasculature in the rat foot-pad, with special reference to vasculature around the eccrine sweat glands. A scanning electron-microscopic study of corrosion casts

The entire microvascular architecture in rat foot-pads including that of eccrine sweat glands was studied by scanning electron microscopy using a vascular corrosion-cast replication technique. In the central roofs of the pads, particularly elaborate capillary networks were arranged in rows perpendicular to the long axis of the foot. In the marginal regions of the pads, simple networks of capillaries were arranged in lamellar sheets parallel to the surface of the sole of the foot. Complex spongy networks of vascular trees were observed in the subcutaneous layer of the pads. These vessels were supplied by the pad artery, and then, after forming capillary networks in the roofs of the pads, they drained into the metatarsal vein. Rod-shaped cages of capillaries were observed around the eccrine sweat glands. One descending arteriole, arising from a connecting arteriole, and a few venules were connected with these capillary cages at their upper and lateral sides. Occasional arterio-venous and veno-venous anastomoses were also observed around the eccrine sweat glands. This microvascular architecture may adjust well to the mechanical and physiological conditions encountered in the foot-pads. The relation of the microvascular architecture around the eccrine sweat glands with their development is also discussed.

The vascular pattern of basal cell tumors: light microscopy and scanning electron microscopic study on vascular corrosion casts

Light microscopy of hematoxylin-eosin stained tissue sections and scanning electron microscopy (SEM) of vascular corrosion casts were used to study the blood vascular system of human basal cell tumors. Concerning the gross angioarchitecture there is a very close correlation between the histological appearance and the findings obtained from vascular corrosion casts, when evaluated in a SEM. The tumor cell beds are enveloped by basket-like capillary plexus. The tumors are traversed over long distances by superficially running, teleangiectatic, but flattened capillaries. These compressed vessels are squeezed between tumor cell cords and epidermis. In vascular corrosion casts of human basal cell tumors the vascular system exhibits three different features. Blind-ending vascular casts; Four different causes for blind-ending cast structures are pointed out and discussed. Incomplete filling of the vascular system; compression of tumor vessels; new proliferating capillary sprouts; broken cast endings. Variations in vessel caliber and extravasation of the injection resin. Most of the variation in vessel calibers are thought to be caused by dilation of the weakened endothelial walls, but some of them presumably represent new projecting vascular swellings. Circumscribed leakage of the injected resin could be attributed to regions of advanced connective tissue degeneration and endothelial lysis. Flattened cast structures; The addition of tissues during tumor growth results in an increase of tissue pressure. Thus many tumor vessels get displaced, compressed, and flattened and vascular occlusions will occur. However, it must be stressed that much caution is needed in assessing the nature of the vascular cast structures of basal cell tumors.