The Song of the Cell: An Exploration of Medicine and the New Human

by Siddhartha Mukherjee

It’s all a circle, so let’s begin with the right side. The right-sided pump collects blood from the veins of the body. Exhausted and depleted, having delivered oxygen and nutrients to the organs, “venous” blood (often darker red than bright crimson) pours into the upper right chamber called the right atrium. It then passes through a valve and is moved into the pumping chamber, the right ventricle. A powerful heave from the right ventricle pumps the blood to the lungs. This is the right-sided circuit—veins to heart to lung. The lungs, having received blood from the right side of the heart, oxygenate the blood and clear the carbon dioxide. Replete with oxygen and cleansed, blood, now a vivid crimson, moves to the left side. It collects in the left atrium of the heart. It is then pushed into the left ventricle. It is this left ventricle, perhaps the most tireless muscle in the body, that ejects the blood forcefully into the wide arc of the aorta, the major blood vessel that carries oxygenated blood to the body, and to the brain.