Four types of tissues are created as cells join and work as a group. Each type of tissue has a unique structure and does a specific job. Muscle tissue is made up of long, narrow muscle cells. Muscle tissue makes the body parts move by tightening and relaxing. Connective tissue is what holds up the body and connects its parts. The bone is made up of connective tissue. Nerve tissue is made up of long nerve cells that go through the body and carry messages. Epithelial tissue is made of wide, flat epithelial cells. This tissue lines the surfaces inside the body and forms the outer layer of the skin. Groups of tissue join together to form the organs in the body, such as the heart, liver, lungs, brain, and kidneys, just to name a few. Then, these organs work together to form our body systems. Each system works together with the other systems of the body.

What job does the epithelial tissue perform?