A group of similar cells that work together to perform a common function is known as a tissue. Four types of tissues exist: epithelial, connective, muscle and nervous. The tissues are classified based on their anatomy and function.
Epithelial tissue covers the surface of the body, lines the spaces inside the body and forms glands. Some examples of this type of tissue include the skin and sweat glands. Connective tissue holds structures in the body together, such as tendons. It also stores energy in the form of fat and produces blood. Muscle tissue contains the cells that are responsible for the contraction of muscles. Nervous tissue is composed of neurons, which transmit information to other cells.