The figure shows the structure of the heart, according to the figure to answer: (1) the heart is mainly composed of ______, divided into four chambers. (2) blood in the heart and blood vessels can onl

The figure shows the structure of the heart, according to the figure to answer: (1) the heart is mainly composed of ______, divided into four chambers. (2) blood in the heart and blood vessels can only press a (1) the heart is mainly composed of myocardium, myocardial cells with automatic rhythmic contraction characteristics, myocardial contraction for the blood circulation to provide power; therefore, the heart is the power organ of blood circulation.

(2) e and f are valves in the heart, called the atrioventricular valve, the atrioventricular valve can only be opened toward the ventricles, which ensures that the blood can only flow in a certain direction, the blood can only flow from the atria to the ventricles, and from the ventricles to the arteries, and can not be reversed. Therefore, the function of the atrioventricular valve is to prevent the backflow of blood.

(3) The circulation of blood in the heart and all the blood vessels in the pipeline system is called blood circulation, according to the different circulatory pathways, the blood circulation is divided into two parts of the body circulation and pulmonary circulation, as shown in the figure:

The answer is: (1) myocardium

(2) ventricles; arteries

(3) the body cycle; the pulmonary circulation

.