- Epithelial tissue is classified based on the shape of the cells at the apical surface and the number of layers of cells.
- This is a thick membrane composed of many layers of scale-like, plate-like, flattened, or squished cells.
- The apical cells are dead due to the fact that they are too far from nourishing blood vessels. The nutrients must diffuse from the blood vessels through all the cell layers. More layers decreases the likelihood the apical cells will receive proper nutrition.
- The basilar cells are metabolically active, producing more cells via mitosis. This replaces the cells that die at the apical surface.
- Protects underlying tissues in regions that are prone to abrasion.
- Protects against pathogen invasion and chemical exposure.
- Also creates a waterproof barrier. (Remember, it is difficult for things to diffuse through many layers of cells)
- Surface of skin
- Lining of mouth, throat, esophagus, rectum, anus, and vagina.