Affixes

The first term in this ending, on which others are modelled, was epithelium (Greek epi, upon), the thin tissue that forms the outer layer of a body's surface or which lines a cavity, that on a teat being taken as the model. Other examples include endothelium (Greek endon, within) is the tissue which forms a single layer of cells lining various organs and cavities of the body, especially the blood vessels, heart, and lymphatic vessels; mesothelium (Greek mesos, middle)is the epithelium that lines the pleurae, peritoneum, and pericardium; the urothelium (Greek ouron, urine) is similarly the epithelium that lines the urinary tract, especially that of the bladder.