Stratified squamous epithelium

A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basement membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural integrity. Although this epithelium is referred to as squamous, many cells within the layers may not be flattened; this is due to the convention of naming epithelia according to the cell type at the surface. In the deeper layers, the cells may be columnar or cuboidal. This type of epithelium is well suited to areas in the body subject to constant abrasion, as it is the thickest and layers can be sequentially sloughed off and replaced before the basement membrane is exposed. It forms the outermost layer of the skin and the inner lining of the mouth, esophagus, and vagina.

Keratinization
Stratified squamous epithelium is further classified by the presence or absence of keratin, a tough protective protein, at the apical surface.

Nonkeratinized
Non-keratinised surfaces must be kept moist by bodily secretions to prevent them drying out and dying.

Types of non-keratinised stratified squamous epithelium include cornea (see also corneal epithelium), oral cavity, esophagus, anal canal, vagina, and the internal portion of the lips

Keratinized
Keratinised surfaces are protected from abrasion by keratin and kept hydrated and protected from dehydration by glycolipids produced in the stratum granulosum.

Types of keratinised stratified squamous epithelium include skin, tongue (filiform papillae), and the external portion of the lips

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