There are four main types of human tissue: epithelia, connective, muscular, and nervous tissue. Epithelia tissue covers surfaces and forms glands. It includes several layers and cell shapes. Connective tissue binds and supports other tissues. The main kinds are connective tissue proper, cartilage, bone, and blood. Muscular tissue is made of cells that contract and relax, including skeletal, cardiac, and smooth muscle. Nervous tissue transmits signals through neurons in the brain, spinal cord, and nerves.