Stratified squamous epithelium. Multiple layers of cells where the surface layer (or luminal layer) of cells appears flattened or squamous.

Caption: Stratified Squamous Epithelium (Keratinized). High-power micrograph of epithelium of sole of foot. Keratinized stratified squamous epithelium covers the surfaces of the palm of the hand and the sole of the foot. Skin that is thick stratified squamous epithelium can also be located in patches on the elbows where protection is needed against abrasion. The most superficial layer observed in this sample of stratified squamous epithelium does not contain live cells. There are no nuclei present near the surface because the cytoplasm of these cells has been completely replaced by a protein called keratin.

Stratified Squamous Epithelium (Keratinized). Multiple layers of cells where the surface layers (or luminal layers) of cells are dead cells. Keratinized stratified squamous epithelium is commonly identified by multiple layers of dead cells where keratin has replaced the nuclei and cytoplasm. This is stratified squamous epithelium because only the basal layer of epithelial cells is in contact with the basement membrane, while the other layers of cells must adhere to neighboring cells as their only means of attachment.

• Microscopic appearance. The deepest (most basal) layer of cells adhering to the basement membrane appear cuboidal to columnar in shape. Those located in the middle layers are polymorphous in shape. The name of stratified squamous epithelium is based on the morphology of the surface cells that are flattened, dead cells.
• Note. These scales of soft keratin remain adherent to the underlying layers of living cells until they are sloughed or scraped off. Keratinized stratified squamous epithelium constitutes a tough layer that resists friction, protects against microbial infection, and is impermeable to water.

Examples of keratinized stratified squamous epithelium include epidermis of the palm of the hand and sole of the foot.