Basal laminas stratified

Figure 1.10 Columnar and stratified epithelia. Epithelial b ssues are underlain by a basement membrane which is a composite structure composed of an amorphous basal lamina, secreted by the epithelial cells, and a more fibrous reticular lamina derived from connective tissue.

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... 

Basal cells that stop dividing also stop secreting a basal lamina and lose their attachment. They are squeezed by adjacent, dividing basal cells into the body of the junctional epithelium and are expelled into the base of a sulcus. The few tight junctions in the body of the junctional epithelium are consistent with its permeability to interstitial fluid. The rapidly dividing cells of both internal and external basal layers express K5 and K14 like all stratified epithelial basal cells, but the interior cells express K4 and K13, not K1 and K10 (Fig. 5.11). The composition of the internal basal lamina is described in Fig. 5.7b. 

The mouth and esophagus are composed of two layers, the mucosa and submucosa (Figure 3.5). The mucosa is lined on its outer surface by a stratified squamous epithelium with layers of polyhedral cells of the intermediate layers and low columnar cells of the basal layer. Below the cellular layer is the lamina propria containing loose connective tissue with blood vessels and small aggregates of lymphocytes. Smooth muscle within the mucosa (muscularis mucosal layer) is seen as small bundles. The submucosa... 

In common with all epithelial interfaces (see Section 1.3.2), the epithelium of the oral cavity is supported by a basement membrane, which separates the epithelium from the underlying connective tissue layer (the lamina propria) (Figure 7.1). Oral epithelium is broadly similar to stratified squamous epithelia found elsewhere in the body, for example the skin (see Section 8.2.1), in that cells are produced by mitosis in the basal layer of the epithelium and these proliferating cells push existing cells towards the surface. The phases of this dynamic process are represented in four morphological layers ... 

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