Epithelial cells are tightly packed cells that form a protective layer covering the surface of your body, lining internal cavities and organs, and forming glands. They act as a barrier between the inside and outside of your body, protecting against infection, injury, and environmental damage. Epithelial cells come in various shapes and arrangements, depending on their function.
Here are some key characteristics of epithelial cells:
- Tightly joined: They are bound together by specialized junctions, creating a continuous sheet.
- Polarity: They have a distinct apical (free) surface facing the exterior or lumen, and a basal surface attached to the underlying connective tissue.
- Avascular: They lack blood vessels and receive nutrients through diffusion from the underlying connective tissue.
- High regenerative capacity: They can readily divide and replace damaged or lost cells.
Epithelial cells play crucial roles in numerous bodily functions, including:
- Protection: They form a barrier against physical, chemical, and microbial insults.
- Absorption: They absorb nutrients and other substances from the environment.
- Secretion: They produce and release substances such as hormones, enzymes, and mucus.
- Filtration: They filter waste products and other substances from the blood.
- Excretion: They remove waste products from the body.
- Sensation: They contain specialized sensory receptors that detect touch, temperature, and other stimuli.
Examples of epithelial cells include:
- Skin: The outer layer of your skin is made up of epithelial cells, which protect against abrasion, infection, and UV radiation.
- Lungs: The lining of the lungs contains epithelial cells that help filter air and protect against infection.
- Intestines: Epithelial cells in the intestines absorb nutrients and water, and also secrete enzymes and mucus.
- Kidneys: Epithelial cells in the kidneys filter waste products from the blood and produce urine.
