Stratified squamous epithelium is a type of epithelial tissue composed of multiple layers of cells, where the superficial cells are flat (squamous) and the deeper layers consist of cuboidal or columnar cells. This arrangement provides protection against mechanical and chemical stress.
Anatomy
- Structure: Multiple cell layers with the basal layer containing cuboidal or columnar cells that undergo mitosis to replace the superficial squamous cells.
- Cell Shape: Cells transition from cuboidal in the basal layer to flat, scale-like cells at the surface.
- Keratinization: In certain locations, this epithelium becomes keratinized with a tough, protective layer of keratin on the surface.
Types
- Keratinized Stratified Squamous Epithelium
- Found in areas exposed to significant wear and tear, such as the skin.
- The surface layer is composed of dead cells filled with keratin, which is waterproof and provides extra protection.
- Non-Keratinized Stratified Squamous Epithelium
- Found in moist environments that experience wear but do not require keratinized protection, such as the oral cavity, esophagus, and vagina.
- The surface cells are alive and lack keratin.
Location
- Keratinized
- Epidermis of the skin.
- Non-Keratinized
- Oral cavity.
- Pharynx and esophagus.
- Vagina.
- Anal canal.
Function
- Protection: Provides a barrier against physical, chemical, and microbial damage.
- Preventing Water Loss: Keratinized epithelium reduces water loss from the body.
- Resilience: Withstands friction and shear forces.
Clinical Significance
- Squamous Cell Carcinoma: A common cancer originating from stratified squamous epithelial cells, often linked to chronic irritation or carcinogens like tobacco.
- Barrett’s Esophagus: Replacement of esophageal stratified squamous epithelium with columnar epithelium in response to acid reflux, increasing cancer risk.
- Skin Conditions: Disorders like psoriasis involve hyperproliferation of keratinized squamous epithelium.
