Britannica Sources used in this answer

How do epithelial tissues protect the body and line internal organs?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram explaining ATP's role in powering cellular activities, with arrows showing ATP produced by mitochondria, chloroplasts, and glycolysis, and used for making biomolecules, transporting substances, and driving energy-requiring processes; includes a structural diagram of ATP with labeled adenine, ribose, and phosphate groups. — Physiology Adenosine triphosphate (ATP) is the power source of many biochemical reactions. It is produced in the cell structures and system listed at the left to energize the important life processes listed on the right. An abbreviated chemical formula of the structure of ATP is also shown. The two high-energy P―O―P bonds are responsible for its power.

Epithelium serves as a vital barrier by forming continuous sheets of closely bound cells that cover body surfaces and line internal cavities. These tissues protect the body through several specialized mechanisms:1

Structural Integrity: Epithelial cells are held together by cell junctions, such as tight junctions that create leakproof seals and desmosomes that distribute mechanical shear force across the tissue to prevent damage from abrasion.23
Stratification: In areas exposed to high friction, such as the skin, stratified epithelium provides multiple layers of protection. Surface cells are constantly shed and replaced by new cells from deeper layers.1
Mucus Secretion: Many internal tracts are lined with mucous membranes, which secrete mucus to trap pathogens and particulate matter, preventing them from reaching deeper tissues while keeping underlying surfaces moist.4
Specialized Modifications: Some epithelial cells produce protective substances like keratin or feature cilia to move substances along respiratory and reproductive tracts.1