Observations on the actual structural conditions in the stratum superficiale dermidis of porcine ear skin, with special reference to its use as model for human skin.

The results obtained from the outer ear skin of female pigs (German Landrace) by light microscopy (LM), transmission electron microscopy (TEM), and cryo scanning electron microscopy (cryo SEM) methods, in particular relying on careful and artefact-free tissue processing, exhibited that the stratum superficiale dermidis of the auricle had a very homogeneous and compact construction, especially in one area (central dorsum auriculae). Based upon the important measurements made [average thickness of stratum superficiale dermidis: 94 (+/-16) microm, region A: 81 (+/-10); average thickness of collagen fibre bundles: 12 (+/-2) microm, region A: 13 (+/-0.5); average density of subepidermal capillaries: 3134 (+/-459) loops/cm2, region A: 3497 (+/-247)], this impression was confirmed by low standard deviations for all parameters, in comparison to marginal locations studied. The capillary system present was analysed by LM and TEM for specific structural features, whereby it generally compared to the microvasculature in human skin. Moreover, a regular pattern of diffusion-relevant punctiform contacts of the capillary loop apex with the epidermal basement membrane became obvious. Cryo SEM, particularly offering the advantages of dispensation of chemical fixation, dehydration and solvents during processing, highlighted delicate structures without shrinkage and without loss of soluble sample components. Thus rather real spatial conditions in the region of the epidermo-dermal junction and the upper dermis were visualized, whereby very regular arrangements of the structures present became obvious. This pertained also to a correct demonstration of all components of the epidermal basement membrane, in particular the lamina lucida. In addition, the water-based stable character of the entire stratum superficiale dermidis could be emphasized as a basic feature for controlled diffusion processes.