Epithelium is a type of tissue that forms the lining of hollow organs and glands, as well as the outer surface of the body. It is made up of tightly packed cells that form a continuous layer.
Epithelial tissues have a wide range of functions, including:
- Protection: Epithelium acts as a barrier to protect underlying tissues from injury, pathogens, and other harmful substances. For example, the skin's epithelium protects our bodies from the environment.
- Absorption: Epithelium in the small intestine absorbs nutrients from digested food.
- Secretion: Glands, which are made up of epithelial cells, secrete substances like hormones, enzymes, and mucus.
- Filtration: Epithelium in the kidneys filters waste products from the blood.
- Diffusion: Epithelium in the lungs allows for the diffusion of oxygen and carbon dioxide between the air and the bloodstream.
- Sensory reception: Epithelium in the nose, tongue, and skin contains sensory cells that allow us to smell, taste, and feel.
Epithelial tissues are classified according to the shape of their cells and the number of cell layers.
- Shapes:
- Squamous: Flat, scale-like cells
- Cuboidal: Cube-shaped cells
- Columnar: Tall, column-shaped cells
- Layers:
- Simple: Single layer of cells
- Stratified: Multiple layers of cells
Examples of epithelial tissues include:
- Skin: The outer layer of skin is made up of stratified squamous epithelium.
- Lining of the mouth: The lining of the mouth is made up of stratified squamous epithelium.
- Lining of the stomach: The lining of the stomach is made up of simple columnar epithelium.
- Lining of the small intestine: The lining of the small intestine is made up of simple columnar epithelium.
- Lining of the lungs: The lining of the lungs is made up of simple squamous epithelium.
Epithelial tissues are vital for maintaining the health and function of the body. They play important roles in protecting us from harm, absorbing nutrients, secreting substances, and regulating many bodily functions.
