Basis of differentiation | Epithelium | Endothelium | Mesothelium |
Definition | Is the thin tissue forming the outer layer of the body’s external surface, lines body cavities and hollow organs, and is the major tissue of glands | Is a single cell layer which lines all the blood and lymphatic vessels. It modulates exchange between the bloodstream and surrounding tissues | Is a protective membrane composed of mesothelial cells which coats the abdomen, heart, lungs and testes |
Function | Its main functions are secretion, adsorption, protection, diffusion, transportation, sensory reception, and filtration | Is the key regulatory of blood fluidity, platelet aggregation, inflammation, and vascular tone | Provides a slippery non-adhesive and protective surface to internal organs, as well as assist in the transport of fluid and cells across serosal cavities |
Characteristics | Epithelial cells are closely packed and form continuous sheets, composed of an apical surface exposed to the body's exterior and a basal surface attached to a basement membrane | Endothelial cells are flat and form a single cell layer to allow for the uninterrupted flow of blood | The mesothelium forms a single cell layer of elongated, flattened, squamous-like mesothelial cells (approximately 25 μm in diameter) |