Diseases are simply the culprits that cause the organs and cells of the human body to fail to function normally. There are many kinds of diseases in the world, even as many as tens of thousands, and different types of diseases bring different harm to the human body, for example, a cold usually has symptoms such as headache, cough and weakness, while chronic gastritis usually has symptoms such as stomach pain. There are many different classifications of diseases, and if they are classified according to the location of onset and treatment characteristics, they can be divided into internal medicine, surgery, gynecology, ophthalmology, stomatology, ENT and so on. In general, when you go to the hospital for examination, the department you choose to register is judged by this, in which internal medicine is a relatively large department, because it mainly contains various organs in the human body, so it can be further subdivided into different systems such as respiratory system, circulatory system, digestive system, blood system, endocrine system and so on. In addition, it can also be divided into infectious and non-infectious diseases according to their contagiousness.