ABSTRACT
Recent cutaneous biology research has successfully explored the complexity of the cutaneous basement membrane zone (BMZ), which by ultrastructural, biochemical and molecular means has been demonstrated to consist of a large number of adhesion complexes. Several of these attachment complexes can be recognized by electron microscopy (Figure 6.1). On the epidermal side, complex structures, known as hemidesmosomes (HD), extend from the cytoplasmic milieu of basal keratinocytes to the extracellular space (Borradori and Sonnenberg, 1996; Green and Jones, 1996). Within the lamina lucida, thread-like structures, known as anchoring filaments, can be recognized by transmission electron microscopy, and they are concentrated predominantly under the HDs and form the HD-anchoring filament complex (Figure 6.1). On the dermal side, anchoring fibrils, attachment structures with a wheat-stack appearance, extend from lamina densa to the underlying dermis (Burgeson, 1993). It has been suggested that one end of anchoring fibrils binds to lamina densa while the other end interacts with basement membrane-like structures, known as anchoring plaques, within the upper papillary dermis (Keene et al., 1987). Intertwining of the anchoring fibrils between the interstitial collagen fibers, which consist primarily of type I, III and V collagens, provides stable association of the lower portion of the dermal-epidermal basement membrane to the underlying dermis (Figure 6.2).
