The Epithelium. Biological & Biomedical Sciences Essay (Essay Sample)

The Epithelium
Epithelial tissues comprise a great portion of the body covering all the surfaces exposed to the outside world and lining the cavities of blood vessels and organs, where they consist of a continuous cellular sheet tightly packed, having little or no extracellular material between the cells (Shier et al., 2015; Ganz, 2002).
Epithelial tissues are separated from the underlying connective tissues by a basement membrane (BM) holding the epithelium together (Shier et al., 2015). Epithelial cells are derived from the three embryonic germ layers (Shier et al., 2015); the mesoderm, ectoderm, and endoderm.
From the ectoderm develops the epithelium covering the skin and the anus. Originating from the endoderm are the epithelial cells lining the airways and most of the digestive system. The epithelium lining the vessels of the lymphatic and cardiovascular systems are derived from the mesoderm and is termed the endothelium.