The human circulatory system is composed of the heart and two vascular systems that carry the blood. The heart is an organ with four compartments called the right atrium, left atrium, right ventricle, and left ventricle.
The walls of the heart are mainly composed of muscle (called myocardium) that contracts to cause the heart to send blood from the left ventricle to the aorta, and from there to the entire body. Arteries carry oxygenated blood and nutrients (sugar, fats, and proteins) from the heart to all organs of the body. The veins return the blood to the heart so that it can be oxygenated again. The non-oxygenated blood reaches the right atrium through the superior and inferior vena cava, passes into the right ventricle and from there to the lungs, where it is “charged” with oxygen and returns to the left atrium to pass to the left ventricle and with the Following heartbeat to nourish our body.
The heart muscle (myocardium) also needs oxygenated, nutrient rich blood in order to function. The arteries that carry oxygenated blood to the heart are the coronary arteries. From the aorta comes a left coronary trunk, which is very short and is divided into two large branches, the anterior descending artery and the circumflex artery, which carry blood to the left side of the heart. The right coronary artery also leaves the aorta, which carries the blood to the right side of the heart. We, therefore, have 3 large coronary vessels: anterior descending, circumflex and right coronary.