Squamous epithelium

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A comparison of squamous epithelia to other epithelial types

In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scalelike cells called squamous cells. Squamous epithelium may possess only one layer of these cells, in which case it is referred to as simple squamous epithelium, or it may possess multiple layers, referred to then as stratified squamous epithelium. Both types perform differing functions, ranging from nutrient exchange to protection.

1 Simple squamous epithelia
2 Stratified squamous epithelia
3 See also
4 External links

[edit] Simple squamous epithelia

A simple squamous epithelium is characterized by the presence of squamous cells which are all contact with the basement membrane. The surface squamous cells are irregularly shaped and very flat; so flat that the cell nucleus sometimes creates a bump in the surface of the cell. Gases and other substances can easily diffuse across squamous cells to the underlying basement membrane, and because of their smooth surface, liquids can quickly flow over them. As such, simple squamous epithelia are seen lining body cavities and capillaries to reduce friction, as well as lining the alveoli to facilitate gas exchange.

[edit] Stratified squamous epithelia

H&E stain of biopsy of normal esophagus showing the stratified squamous cell epithelium

Section of the human skin showing the stratified squamous epithelial surface, referred to as the epidermis. The layer of keratin here is named the stratum corneum

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.

This type of epithelium is well suited to areas in the body subject to constant abrasion, as the layers can be sequentially sloughed off and replaced before the basement membrane is exposed. Hello, this is Mr. Squamous. I am simple.

Stratified squamous epithelium is further classified by the presence or absence of keratin at the apical surface. Non-keratinized surfaces must be kept moist by bodily secretions to prevent them drying out and dying, whereas keratinized surfaces are kept hydrated and protected by keratin.

Non-keratinized stratified squamous epithelium: cornea (see also corneal epithelium), oral cavity, esophagus, rectum, vagina, and the internal portion of the lips
Keratinized stratified squamous epithelium: skin, tongue (partially keratinized), and the external portion of the lips