A tissue is made up of a group of similar cells that function together in the body.
Humans have four basic types of tissues.
Epithelial tissue consists of tightly packed cells, attached to a basement membrane, that line body cavities or surfaces opening to the outside. It is named according to the shape of its cells. Epithelial tissues are specialized for protection, absorption, and secretion. Epithelium can be stratified or simple. Pseudostratified epithelium appears layered but is not.