Epithelial tissue is a type of tissue that forms the protective outer layer of the body and lines internal organs and cavities. It consists of closely packed cells with minimal extracellular matrix, allowing for efficient absorption, secretion, and sensation. Epithelial tissue is classified into different types based on cell shape and arrangement, including squamous, cuboidal, and columnar. This tissue serves several essential functions, such as protecting underlying structures, facilitating the exchange of materials, and producing various substances like mucus and hormones. Epithelial tissue is also involved in sensory perception, as it contains specialized cells that respond to stimuli, contributing to the body's overall function and health.