The heart is located in the mediastinum in the middle of the thoracic cavity, above the diaphragm and between the two lungs, with about 2/3 on the left side of the midline and 1/3 on the right side of the midline. The front of the heart is mostly covered by the lungs and the lining of the thoracic cavity, only a small part of it is directly adjacent to the sternal body and rib cartilage of the thorax by means of the pericardium, and on both sides it is adjacent to the lungs and the thoracic cavity, posteriorly to the esophagus, nerves and aorta, etc. Below it is the diaphragm that separates the thoracic and abdominal cavities, and above it is connected to the great vessels of the heart (aorta, pulmonary artery, etc.). The heart is a hollow muscular organ with four chambers: the posterior upper part is the left atrium and the right atrium, separated by the interatrial septum; the anterior lower part is the left ventricle and the right ventricle, separated by the interventricular septum. Under normal conditions, the left and right halves of the heart do not communicate directly with each other because of the separation of the atrial and ventricular septum, but each atrium can pass through the atrioventricular opening to the ipsilateral ventricle. According to the direction of blood flow, the right atrium has three entrances and one exit: the entrances are the superior and inferior vena cava ports and the coronary sinus port. The coronary sinus orifice is the main entrance of venous blood from the heart wall back to the heart; the outlet is the right atrioventricular orifice, through which the right atrium leads to the right ventricle. The oval depression in the lower posterior part of the atrial septum is called the fossa ovalis, which is a remnant of the atresia of the foramen ovale that connected the left and right atria during the embryonic period. The upper part of the right atrium protrudes anteriorly to the left as the right auricle. The right ventricle has two ports of entry and exit: the entrance is the right atrioventricular port, which is surrounded by three blade-like valves, called tricuspid valves (i.e., right atrioventricular valves). The valve is divided into anterior, posterior, and septal valves according to its position. The valves hang down toward the ventricular cavity and are connected to the papillary muscles on the ventricular wall with the help of many thread-like tendons; the outlet is the pulmonary artery orifice with three semilunar valves on its circumference, called the pulmonary valve. The left atrium constitutes the majority of the fundus of the heart and has four entrances and one exit: on each side of the posterior wall of the left atrium, there is a pair of pulmonary vein ports, which are the entrances to the left and right pulmonary veins; under the anterior part of the left atrium there is the left atrioventricular port, which leads to the left ventricle. The anterior part of the left atrium protrudes to the right anteriorly and is called the left auricle. The left ventricle has two entrances and exits: the entrance is the left atrioventricular opening, with a mitral valve (left atrioventricular valve) attached to its circumference, which is divided into anterior and posterior valves according to their position, and they also have tendons connected to the anterior and posterior papillary muscles respectively; the exit is the aortic opening, which is located above the right anterior to the right atrioventricular opening, with a semilunar-shaped aortic valve attached to its circumference. The human heart is a tireless power pump, the main role is to promote the flow of blood, the heart around the clock from the veins into the right side of the heart (from the right atrium into the right ventricle), and then pump blood into the lungs, blood in the lungs to receive oxygen into the left side of the heart, through the left atrium to the left ventricle and then shot into the arteries, through the aorta and branches throughout the body to transport blood to various organs and tissues of the body The blood is then pumped to the left side of the heart, through the left atrium to the left ventricle and then into the arteries.