The body’s valves allow blood to flow only in one direction. This supports the two cycles observed in human circulation: that of arterial blood, which has been oxygenated by the lungs and will be distributed throughout the body when the heart pumps, and venous blood, which returns to the deoxygenated heart and rich in carbon dioxide.
Deoxygenated blood enters the heart through the superior vena cava and inferior vena cava, flowing into the right atrium. The muscles of this chamber relax and the space is filled with the venous blood, and then it is controlled by an orifice to the right ventricle. Functioning like a pump, the right ventricle pushes the blood to the lungs.
Once restored and again rich in oxygen, the blood returns to the left side of the heart through the pulmonary veins. First it reaches the left atrium, following an orifice to the left ventricle. Being the most powerful chamber of the heart, it generates strong contractions to pump the blood to the whole body through the exit port: the aorta artery.
Although it is one of the major responsible for the distribution of oxygen to the body, the heart also needs to receive oxygen to function properly. In this way, your muscles are nourished by a network of arteries – the coronary arteries – that originate in the aorta.
To pump blood properly, the organ relies on electrical signals sent by the sinoatrial node (the “natural pacemaker”) to the heart cells. In response, these cells produce the contractions necessary to push the blood to all tissues in the body.