Epithelial tissue
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In addition to connective tissue, muscle tissue, and nerve tissue, epithelial tissue is one of the four main forms of tissue in the human body. It consists of sheets of closely packed cells that cover and line the exterior and interior surfaces and cavities of the body.
Epithelial Tissue Types
- There are several forms of epithelial tissue, such as:
- Simple Squamous Epithelium: A single layer of flat cells that coat the linings of the lungs, blood arteries, and body cavities.
- Stratified Squamous Epithelium: Several layers of flat cells line the skin, mouth, and esophagus.
- Simple Cuboidal Epithelium: A single layer of cube-shaped cells that line the ducts of the kidneys and other glands.
- Stratified Cuboidal Epithelium: Several layers of cube-shaped cells that line the sweat glands and other exocrine glands.
- Simple Columnar Epithelium: A single layer of tall, slender cells that coat the digestive tube.
- Pseudostratified Columnar Epithelium: A single layer of cells that appear to be many layers due to height discrepancies and the presence of cilia, lining the respiratory system.
Functions of Epithelial Tissue
- Epithelial tissue serves several crucial tasks, including:
- Protection: Epithelial tissue produces a barrier that prevents physical, chemical, and biological harm to the interior surfaces of the body.
- Secretion: Epithelial cells release hormones, enzymes, and mucus, among other items.
- Absorption: Epithelial cells absorb nutrients, water, and other elements from the outside environment of the organism.
- Sensation: Epithelial cells include sensory receptors that sense environmental changes in the body, such as temperature, pressure, and touch.
Descriptive Features of Epithelial Tissue
- Many properties separate epithelial tissue from other forms of tissue, including:
- Cellularity: The cellularity of epithelial tissue consists of densely packed cells with little extracellular matrix.
- Polarity: Epithelial cells have an apical surface that contacts the external environment and a basal surface that adheres to the tissues beneath.
- Avascularity: Without blood arteries, epithelial tissue relies on diffusion to receive nutrients and discharge waste.
- Regeneration: Epithelial tissue has a strong regenerative ability and can rapidly replace or repair injured or destroyed cells.
Also see
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