Stratified squamous epithelium is a type of epithelial tissue composed of multiple layers of flat cells stacked on top of each other. The term "stratified" means the cells are arranged in layers, "squamous" refers to the flat shape of the cells in the outermost layers, and "epithelium" denotes a tissue made of tightly packed cells forming a protective lining or covering.
This epithelium is primarily protective, designed to withstand mechanical stress, abrasion, and microbial invasion. It is found in areas subject to heavy wear and tear, such as the skin surface, inside the mouth, esophagus, and vagina.
There are two main types based on keratin presence:
- Keratinized stratified squamous epithelium has a tough outer layer of keratin, a fibrous protein that protects against heat, microbes, and water loss. This type is typical of the skin's outer layer.
- Non-keratinized stratified squamous epithelium lacks significant keratin and remains moist, found in internal moist surfaces like the oral cavity, esophagus, and vagina.
The cells in the basal layer are cuboidal or columnar and continuously divide, pushing older cells toward the surface, where they flatten and eventually shed.
In summary, stratified squamous epithelium is a multi-layered, flat-cell tissue specialized for protection, with variations adapted to dry or moist environments depending on keratinization.
