Normal human body fluids include intracellular fluids and extracellular fluids, generally intracellular fluids refer to the fluids inside the cells, and extracellular fluids refer to the fluids outside the cells. Intracellular fluid accounts for 2/3 of human body fluids, while extracellular fluid accounts for only 1/3 of human body fluids. extracellular fluid also includes plasma, tissue interstitial fluid (referred to as tissue fluid or intercellular fluid), as well as cerebrospinal fluid and lymphatic fluid, which is the composition of extracellular fluid. 1/5 of the extracellular fluid is plasma, which is the fluid that exists inside blood vessels, and the remaining 4/5 is tissue fluid and exists in the intercellular spaces. The general gastrointestinal tract also secretes fluid, and the amount of this fluid varies with eating and drinking. These are the components of body fluids.