BASIC STRUCTURE OF THE HEART
Heart is a muscular organ the function of which is to pump the oxygen and nutrient-rich blood to different parts of the body. This is done by vessels called “arteries” (except the pulmonary artery which carries impure blood). The impure blood on the other hand, is carried back to the heart by vessels called “veins” (except the pulmonary vein which carries pure blood).
The pure and impure blood inside the adult heart is separated by a wall (septum) which divides the heart in two separate parts. Each part is further subdivided into upper and lower chambers. The upper ones receives the blood and lower ones pump the blood out. The left upper chamber (left atrium) receives pure blood from the lungs and passes it to the left lower chamber (left ventricle) through a valvular opening (mitral valve). This valvular opening then pumps the oxygen-rich blood to different parts of the body. The right upper chamber (right atrium) receives impure blood through veins and passes it to the right lower chamber (right ventricle), through the valvular opening (tricuspid valve), which then pumps it to the lungs for oxygenation.
In order to reach different organs, blood has to be pumped at a high pressure. The heart muscles work very hard to make this happen (especially the left ventricles) and need a good supply of oxygen (hence blood). This is accomplished through vessels called coronary arteries.
The coronary arteries and its branches not only supply blood to the heart muscles but also to the electrical impulse conducting system. The left coronary artery is larger and divided into two arteries – the anterior descending artery and circumflex artery. It supplies blood to most of the left atrium, left ventricle and inter ventricular wall. The right coronary artery is smaller and supplies blood to the right atrium and most of the right ventricle. This means the blood supply to the muscles of heart is through three arteries namely left anterior descending, left circumflex and right coronary artery. The blood flows in these coronary arteries only between beats when the heart muscles relax (i.e. during diastolic phase).