GENERAL HISTOLOGY

Detailed explanation-1: -The upper surface of epithelium is free, or exposed to the outside of the body or to an internal body cavity. The basal surface rests on connective tissue. A thin, extracellular layer called the basement membrane forms between the epithelial and connective tissue.

Detailed explanation-2: -Basic Structure of Epithelia Epithelia are polarized, with an apical surface that faces the external environment and a basal surface that faces the basement membrane.

Detailed explanation-3: -The bottom edge of the epithelial tissue next to the basement membrane is the basal surface. In contrast, the edge of the epithelial tissue facing the lumen or the external environment is called the apical surface.

Detailed explanation-4: -Simple squamous epithelial cells are thin and flat (the thinnest of all epithelial cell-types), which allows them to have a large surface area that is exposed to the lumen on one side (the apical surface), and to the basement membrane (i.e. basal lamina) on the other (the basolateral surface; Figure 1).