Fluid exhaustion is often caused by excessive sweating, vomiting, diarrhea, and diuresis, or due to excessive blood loss, prolonged illness leading to depletion of essence and blood, or misuse of pungent, warm, and drying substances, resulting in zang-fu organs' fluid deficiency and damage. This leads to the zang-fu organs' tissues and orifices losing their moistening and nourishing functions. Therefore, zang-fu organs' fluid deficiency is also referred to as "dryness," and in severe cases, it can develop into "yin deficiency" or "blood dryness." During the course of a disease, the extent of body fluids' depletion varies, and the affected zang-fu organs differ, leading to different manifestations of zang-fu organs' body fluids deficiency. This section focuses on the mechanism of disease involving the lungs, stomach, and large intestine's fluid injury. For more details, refer to the chapter on zang-fu organs' mechanism of disease.