Basal laminas hemidesmosomes

Plakin proteins link intracellular keratin intermediate filaments to hemidesmosomes of basal epidermal cells, or to desmosomes on suprabasal epidermal cells (Sect. 5.2.1), whereas type XVII collagen (the only collagen secreted by epithelial cells ) and integrins attach hemidesmosomes to a basal lamina. Three p 1 integrins (with al, a3 or a5 partners)... 

A basal lamina is permeable to interstitial fluid which provides the nutrients for the basal layer of cells to proliferate. As discussed in Sect. 5.1, basal cells adhere to the basal lamina using hemidesmosomes. In simple epithelia, basal cells either divide into identical daughter cells or undergo apoptosis (programmed cell death, Sect. 13.4.1). In a stratified... 

In epithelial cells, integrin a6(34 is concentrated in hemidesmosomes and plays a major role in adhering cells to matrix in the underlying basal lamina, as discussed in detail in Section 6.3. Some integrins, particularly those expressed by certain blood cells, participate in heterophillc cell-cell interactions. The members of this large family play important roles in adhesion and signaling in both epithelial and nonepithelial tissues. 

Cell-surface adhesion receptors (e.g., a6p4 integrin in hemidesmosomes) anchor cells to the basal lamina, which in turn is connected to other ECM components (see Figure 6-1). 

The basement membrane zone or epidermal-dermal junction is a thin extracellular matrix that separates the epidermis from the dermis. It is a highly specialized structure recognized with the light microscope as a thin, homogeneous band. Ultra-structurally, it can be divided into four component layers (1) the cell membrane of the basal epithelial cell, which includes the hemidesmosomes (2) the lamina ludda (lamina rara) (3) the lamina densa (basal lamina) and (4) the subbasal lamina (sublamina densa or reticular lamina), with a variety of fibrous structures (anchoring fibrils, dermal microfibril bundles, microthreadlike filaments) (Briggaman and Wheeler, 1975). The basement membrane has a complex molecular architecture with numerous components that play a key role in adhesion of the epidermis to the dermis. The macromolecules that are ubiquitous components of all basement membranes... 

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