[Recent morphologic and experimental results on the normal and impaired function of cutaneous vascular organ]

The objective of this article is to briefly review our present knowledge of the pattern, the functional behaviour and the fine structure of the cutaneous papillary vessels and their alterations under various pathological conditions. The shape of these capillary loops varies within wide ranges dependant on the functional state of the covering epidermis. If the latter is hyperplastic the vessels are elongated, twisted and coiled. In case of epidermal atrophy the capillaries become shorter, decrease in number until their final complete absorption. At the level of the electron microscope the capillary wall clearly shows to consist of 2--3 or more endothelial cells of high electron density encircling an always narrow lumen. Both the inner and outer endothelial surfaces are irregular in outline and the cytoplasm is crowded with filaments of 50--70 A in diameter. In addition it is characterized by the occurrence of a larger number of vacuoles and Weibel-Palade bodies, the latter serving as an excellent marker for endothelial cells to e.g. clearly decide the morphogenesis of certain vascular tumors. Along their apex the capillary loops show a fenestrated endothelium particularly at their adepidermal sites. The basal lamina is multilayered and thereby giving a scroll-like appearance in cross sections. At the ultrastructural level endothelial cells are only provided with a limited repertoire of reactions to noxious stimuli. Among these are: (1) an increase in vesiculation and organelles, (2) the formation of cytoplasmic processes often accompanied by the development of interendothelial "gaps" and (3) alterations - mostly thickenings - of the basement membrane. These different fine structural changes were shown to also occur in various diseases of the skin including it's vascular tumors. In experimental research of the skin microvasculature the most spectacular technique was that of a human skin chamber as originated by Branemark. Thereby most of our older findings as to the functional behavior of the microcirculation in laboratory animals were shown to be valid and hence transferable to humans provided similar experimental approaches were used. Finally the vitalmicroscopy and ultrastructure of tumors (melanoma, hemangiopericytoma and neurilemmoma) transplanted into the hamster cheek pouch are briefly outlined.