Below the left rib cage are mainly the heart, lungs, stomach and other organs. 1. Heart: The heart is positioned to the left in the chest cavity, with atrial and ventricular structures, and its main role is to push blood from the arteries to various organs throughout the body, providing oxygen and nutrients to the tissues and organs, and maintaining the pumping function of the human body. In addition, the heart also secretes some hormones, such as atrial natriuretic peptide, which plays the role of diuretic sodium discharge. 2. Lungs: The lungs are located on the left and right ribs, and maintain the respiratory function of the human body by inhaling oxygen and discharging carbon dioxide to complete gas exchange. In addition, the lungs are also involved in metabolism, filtering out harmful substances in the human body, but also like phlegm. The outside of the lungs is also wrapped with a layer of pleura, which can play a protective function for the chest cavity. 3. Stomach: The stomach is located on the left side of the abdomen under the ribs, where it can store food and secrete gastric juice to digest food. There is a mucous membrane on the outside of the stomach as a protective barrier to prevent pathogens from invading. If there is pain in the left side of the rib cage against the epigastrium, it is usually considered to be a disease of the stomach. In addition, the pancreas and spleen are also distributed between the ribs, if the patient has pain in the left side of the ribcage area is likely to be the disease of the above organs, it is necessary to consult a doctor in time to clarify the cause of the disease, so as not to delay the condition.