A muscular organ, the heart is located under the ribcage between the right and left lungs. Its size depends on a person’s age, size and condition. In a healthy, average-sized adult, it is almost the size of a fist. The right side of the heart receives blood from the organs of the body and pumps it to the lungs. Blood gets oxygenated in the lungs and is pumped out through the left side of the heart. Therefore, the heart can be considered as two pumps in one. It is the centre of the body’s circulatory system.
The heart consists of four chambers. Two chambers are found on each side of the heart. One chamber is on the top; another chamber is on the bottom. The two chambers on top are called the atria; a single chamber is called an atrium. Basically, the atria receive and collect blood returning from the lungs. The heart has a left atrium and a right atrium. The two chambers on the bottom are known as the left ventricle and right ventricle. The pumping action of the ventricles pushes out blood from the heart to the body and lungs. A thick muscular wall called the septum divides the left and right sides of the heart.
The atria and ventricles work in synchronization. When the atria is filled with blood, it is pumped into the ventricles. The ventricles then contract to push blood out of the heart. While the ventricles are squeezing, the atria refills and gets ready for the next contraction. For the heart to function properly, blood must flow only in one direction. This is made possible by four special valves: mitral, tricuspid, aortic and pulmonary valves. Each value has a set of flaps called cusps. Working together, they regulate the flow of blood in the heart, its chambers and arteries.
The mitral valve and the tricuspid valve let the blood flow from the atria to the ventricles. The other two, called the aortic valve and pulmonary valve, control blood flow from the heart. These valves work to keep the blood flowing forward. They open to let the blood flow ahead; they then close quickly to stop the blood from flowing backward. Healthy valves work in coordination with the pumping actions.
The left side of your heart sends oxygen-rich blood out to the body. The body cells use the oxygen, and produce carbon dioxide and wastes that are carried away by the blood. The returning blood enters the right side of the heart. The right ventricle pumps the oxygen-poor blood to the lungs for rejuvenation. In the lungs, carbon dioxide is removed from the blood and expelled away from the body when we exhale. When we inhale, we breathe in oxygen, which passes from your lungs into the blood. The process is then repeated. How do the different parts of the heart work in coordination? Each beat of the heart is set in motion by an electrical system from within the heart muscle.
Place your ear on your friend’s chest, and you will hear a lub-dub sound. The “lub” sound comes from the closing of the mitral and tricuspid valves. The “dub” sound (the dub) happens when the aortic and pulmonary valves close after the blood has been pumped out of the heart. Every time your heart beats, it also creates a pulse on arteries close to the surface of the skin. You can count your heartbeat by taking your pulse on the artery at the wrist or neck (along the outer edge of the windpipe). The normal resting pulse rate is 60-100 beats for an adult. An unusually high or low pulse rate may indicate an underlying problem.
Once blood leaves the heart, it moves through many tubes called arteries and veins. They are collectively called blood vessels, and are attached to the heart. It takes less than 60 seconds to pump blood to every cell in your body. Arteries carry blood away from the heart; veins carry blood back to the heart. Capillaries are the smallest of blood vessels where exchange of oxygen and nutrients takes place between tissue cells and blood.