Epithelial tissue
Epithelial Tissue
Epithelial tissue (pronounced: /ˌɛpɪˈθiːliəl ˈtɪʃuː/), also known as epithelium, is one of the four basic types of animal tissue that lines the cavities and surfaces of structures throughout the body. The term "epithelium" comes from the Greek words "epi" (upon) and "thelē" (nipple), referring to its positioning on the body's surfaces.
Function
Epithelial tissue serves several key functions, including protection, secretion, absorption, and filtration. The cells of the epithelial tissue are tightly packed together to form a protective barrier against physical damage, pathogens, and fluid loss.
Types
There are several types of epithelial tissue, classified by the shape of the cells and the number of layers. These include:
- Simple epithelium: This type of epithelial tissue consists of a single layer of cells. It is involved in diffusion, osmosis, and filtration. Examples include the alveoli in the lungs and the glomeruli in the kidneys.
- Stratified epithelium: This type of epithelial tissue consists of multiple layers of cells. It is involved in protection against physical and chemical wear and tear. Examples include the skin and the lining of the mouth.
- Pseudostratified epithelium: This type of epithelial tissue appears to have multiple layers due to the irregular positioning of the nuclei, but all cells are in contact with the basement membrane. It is involved in secretion and movement of mucus. Examples include the trachea and bronchi.
- Transitional epithelium: This type of epithelial tissue can change its shape in response to tension. It is involved in the stretching of urinary organs. Examples include the bladder and ureters.
Related Terms
- Basement membrane: A thin, fibrous extracellular matrix of tissue that separates the epithelium, mesothelium, and endothelium from underlying connective tissue.
- Endothelium: The thin layer of simple squamous cells that lines the interior surface of blood vessels and lymphatic vessels.
- Mesothelium: The epithelium that lines the pleurae, peritoneum, and pericardium.
External links
- Medical encyclopedia article on Epithelial tissue
- Wikipedia's article - Epithelial tissue
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