Stratified epithelium

Stratified epithelium is a type of epithelial tissue composed of multiple layers of cells. This tissue type is primarily involved in providing protection against mechanical and chemical stress. The cells in the deeper layers are usually cuboidal or columnar, while the cells in the outermost layer are flattened and squamous.

Structure

Stratified epithelium is characterized by several layers of cells, with the basal layer attached to the basement membrane. The cells in the basal layer are typically cuboidal or columnar and are capable of cell division. As new cells are produced, they push older cells toward the surface, where they become more flattened and squamous in shape.

Types

There are several types of stratified epithelium, each with distinct characteristics and functions:

• Stratified squamous epithelium: This type has multiple layers of cells with the outermost layer being flat and scale-like. It can be further divided into keratinized and non-keratinized types. The keratinized type is found in areas subject to abrasion, such as the epidermis of the skin, while the non-keratinized type is found in moist areas like the esophagus and vagina.

• Stratified cuboidal epithelium: This type consists of multiple layers of cube-shaped cells. It is relatively rare and is found in the ducts of some glands, such as the sweat glands and salivary glands.

• Stratified columnar epithelium: This type has multiple layers with the surface cells being columnar in shape. It is also rare and can be found in parts of the pharynx, the male urethra, and some glandular ducts.

Function

The primary function of stratified epithelium is to protect underlying tissues from mechanical and chemical stress. The multiple layers of cells provide a robust barrier that can withstand abrasion and other forms of physical damage. In keratinized stratified squamous epithelium, the presence of keratin adds an additional layer of protection and waterproofing.

Location

Stratified epithelium is found in areas of the body that are subject to significant wear and tear. Examples include:

• The outer layer of the skin (epidermis)
• The lining of the mouth, esophagus, and vagina
• The ducts of certain glands, such as the sweat glands and salivary glands
• Parts of the pharynx and the male urethra

Related Pages

• Epithelial tissue
• Simple epithelium
• Squamous epithelium
• Cuboidal epithelium
• Columnar epithelium
• Keratin
• Basement membrane