Tissues are groups of similar cells that work together to perform a specific function. There are four main types of tissues in the human body: 1. Epithelial tissue: Covers body surfaces, lines body cavities, and forms glands. It protects, secretes, absorbs, and excretes. Examples include the skin and the lining of the digestive tract. 2. Connective tissue: Supports, connects, or separates different types of tissues and organs. It is the most abundant and widely distributed tissue type. Examples include bone, cartilage, blood, and adipose (fat) tissue. 3. Muscle tissue: Specialized for contraction, which produces movement. There are three types: skeletal muscle (voluntary movement), smooth muscle (involuntary movement in organs), and cardiac muscle (involuntary movement in the heart). 4. Nervous tissue: Composed of neurons and glial cells. It transmits electrical signals throughout the body, allowing for communication and coordination. Found in the brain, spinal cord, and nerves.