Squamous epithelium is one of several types of epithelia.

In anatomy, squamous epithelium (from Latin squama, "scale") is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous cell. Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called 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.

Simple squamous epithelia

A simple squamous epithelium is characterized by the presence of squamous cells that are all in contact with the basement membrane. The basement membrane is a structure that supports overlying Epithelial or Endothelial cells. The cells are irregularly shaped and very flat, so flat that the cell nucleus sometimes creates a bump in the surface of the cell. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed 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. Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement As such, simple squamous epithelia are seen lining body cavities and capillaries to reduce friction, as well as lining the alveoli of the lung to facilitate gas exchange. In Anatomy, a serous membrane (or serosa) is a smooth membrane consisting of a thin layer of cells which excrete Serous fluid Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange An alveolus (plural alveoli, from Latin alveolus, "little cavity" is an anatomical structure that has the form of a hollow cavity lung is the essential Respiration organ in air-breathing Animals including most Tetrapods a few Fish and a few Snails The most primitive Gas exchange or respiration takes place at a respiratory surface—a boundary between the external environment and the interior of the body

Stratified squamous epithelia

Stratified squamous epithelium is characteristic of the normal lining of the esophagus, as seen in this section. The esophagus or oesophagus (see American and British English spelling differences) sometimes known as the gullet, is an organ in

The epidermal layer of human skin is formed by stratified squamous epithelium. The skin is the outer covering of living tissue of an animal (or plant

A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basement membrane. In biology and medicine epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body The basement membrane is a structure that supports overlying Epithelial or Endothelial cells. 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.

Stratified squamous epithelium is further classified by the presence or absence of keratin at the apical surface. Keratins are a family of fibrous structural proteins; tough and insoluble they form the hard but nonmineralized structures found in Reptiles Birds Non-keratinised surfaces must be kept moist by bodily secretions to prevent them drying out and dying, whereas keratinised surfaces are kept hydrated and protected by keratin.

• Non-keratinizing stratified squamous epithelium (SSNKE): cornea (see also corneal epithelium), oral cavity, esophagus, rectum, vagina, and the internal portion of the lips
• Keratinizing stratified squamous epithelium (SSKE): skin, tongue (partially keratinised), and the external portion of the lips

See also

• Squamous cell carcinoma

External links

• Histology at KUMC epithel-epith02 Simple squamous epithelium of the glomerulus (kidney)
• Diagrams of simple squamous epithelium
• Histology at KUMC epithel-epith12 Stratified squamous epithelium of the vagina
• Histology at KUMC epithel-epith14 Stratified squamous epithelium of the skin (thin skin)
• Histology at KUMC epithel-epith15 Stratified squamous epithelium of the skin (thick skin)
• Stratified squamous epithelium of the esophagus