This picture shows the structure of the human heart. (1) Write the names of the following structures: A, _ _ _ _ _ D, _ _ _ _ _ B, _ _ _ _ _ G, ______(2) Heart.

(1) As shown in the figure, the structure of the heart is named as: A left atrium, B left ventricle, C right atrium, D right ventricle, A aorta, B pulmonary artery, C pulmonary vein, D superior vena cava, E arterial valve, F arterial valve and G inferior vena cava.

(2) The heart keeps beating. Its contraction and relaxation are like a pump, which transports blood to all parts of the body. The heart is mainly composed of muscle tissue.

(3) The circulation of blood in the pipeline system composed of the heart and all blood vessels is called blood circulation. According to different circulation routes, blood circulation can be divided into systemic circulation and pulmonary circulation. The way of blood circulation is as follows:

That is, in the four chambers of the heart, arterial blood flows in the left ventricle and left atrium, and venous blood flows in the right atrium and right ventricle; Arterial blood flows in aorta and pulmonary vein, while venous blood flows in superior vena cava and pulmonary artery.

(4) The thicker the heart wall, the more developed the muscle, and the stronger the contraction and relaxation, which is in line with the blood transfusion function of each cavity of the heart. The wall of the ventricle is thicker than that of the atrium. The contraction of the ventricle can transport blood to the capillaries of the whole body, and the atrium only needs to send blood to the ventricle. The distance that the ventricle transports blood is longer than that of the atrium. The left ventricular wall is thicker than the right ventricular wall. The contraction of the left ventricle transports blood to the capillaries of the whole body, and the contraction of the right ventricle transports blood to the lungs. The distance that the left ventricle transports blood is longer than that of the right ventricle. The left atrium communicates with the left ventricle, and the right atrium communicates with the right ventricle. The left and right ventricles are not connected: there are valves between atria and ventricles and between ventricles and arteries, which can prevent blood from flowing back. Therefore, the left ventricle is the thickest of the four chambers of the heart.

(5) Between atria and ventricles, and between ventricles and arteries, there are valves that can be opened and closed: these valves can only be opened in one direction: atrioventricular valves can only be opened to ventricles, and arterial valves can only be opened to arteries. This ensures that blood can only flow in one direction: blood can only flow from atrium to ventricle, and from ventricle to artery, but not vice versa.

So the answer is: (1) left atrium; Right atrium; Pulmonary artery; inferior vena cava

(2) Muscle tissue

(3)D

(4)B left ventricle

(5) valves; Drive in one direction