noun, plural: epithelial cells
Animals have different types of tissues such as the epithelial tissue, muscle tissue, connective tissue, and nervous tissue. The epithelial tissue is an animal tissue that lines the cavities and surfaces of structures of an animal body. This tissue also lines certain glands especially ones that are involved in secretion, selective absorption, protection, transcellular transport and the detection of sensation.
The epithelial tissue is made up of a group of cells called epithelial cells. Etymologically, the word epithelial is derived from the Greek word epi meaning on or upon and thele meaning nipple.
Epithelial cells that form the epithelium are responsible for the following functions: protection (of underlying structures), secretion, regulation, and absorption. Epithelial cells may be classified according to their shape:
- squamous epithelial cells
- columnar epithelial cells
- cuboidal epithelial cells
Squamous epithelial cells are thin, flat cells looking like scales. They appear polygonal in shape when viewed from above. Columnar epithelial cells are rectangular, i.e. the cells appear taller than wide. Cuboidal epithelial cells are cube-shaped, i.e. the height and width of the cells are approximately the same.