Human body tissues mainly include four major tissues such as epithelial tissue, connective tissue, muscle tissue and nerve tissue. 1. The epithelial tissue, also known as the epithelium, is the largest tissue in the human body, but also an important structure covering other tissues, mainly composed of epithelial cells and a small amount of interstitial cells, with the protection, astringent and excretory, secretion and other functions, the skin, mucous membranes, glands belong to the epithelial tissue. 2. connective tissue consists of cells and a large number of interstitial cells, in which the cells are dispersed in the interstitial cells. Connective tissue has the role of connection, support and nutrition, protection. 3. Muscle tissue is a tissue composed of special muscle cells, which are relatively slender in form, so it is also called muscle fiber. Because of its contractile nature, it is also the main driving force for the realization of physiological functions of the body, limbs and internal organs. 4. Nervous tissue is an important part of the nervous system, consisting of nerve cells and glia, whose main role is to receive, integrate and transmit information. Each tissue has its own function, and various tissues and organs work together to realize the physiological functions of the human body.