The heart is a muscular organ that continuously pumps blood throughout the body. This pumping action sustains life by carrying oxygen and nutrients to cells and tissues. It also removes waste products, ensuring organs function correctly.
The Heart’s Two Sides
The heart is divided into two sides, separated by a muscular wall called the septum. This septum prevents the mixing of oxygen-rich and oxygen-poor blood.
The left side of the heart pumps oxygen-rich blood. This oxygenated blood travels from the lungs to the left side, then distributes to the rest of the body. Conversely, the right side handles oxygen-poor (deoxygenated) blood. This blood returns from the body’s tissues to the right side, which then pumps it to the lungs to pick up oxygen. Each side contains two chambers: an upper atrium and a lower ventricle. The right atrium receives deoxygenated blood from the body, passing it to the right ventricle, which sends it to the lungs. The left atrium receives oxygenated blood from the lungs, moving it into the left ventricle, which pumps it out to the body.
The Journey of Blood and Oxygen
Blood becomes oxygen-rich and circulates through two main pathways: pulmonary and systemic circulation. Pulmonary circulation begins with oxygen-poor blood entering the right side of the heart. This deoxygenated blood is pumped from the right ventricle into the pulmonary artery, carrying it to the lungs.
Within the lungs, in tiny air sacs called alveoli, an exchange occurs. Oxygen from inhaled air diffuses across the alveoli walls into surrounding capillaries, enriching the blood. Simultaneously, carbon dioxide from body cells diffuses from the blood into the alveoli to be exhaled. This transforms oxygen-poor blood into oxygen-rich blood.
Once oxygenated, this blood returns from the lungs to the left side of the heart through the pulmonary veins. This completes pulmonary circulation and starts systemic circulation. The oxygen-rich blood enters the left atrium, then moves into the left ventricle. The left ventricle pumps this oxygenated blood into the aorta, the body’s largest artery.
From the aorta, arteries and capillaries distribute oxygen-rich blood to all body tissues and organs. In the capillaries, oxygen and nutrients are delivered to cells, while carbon dioxide and other waste products are picked up. The blood, now oxygen-poor, returns to the heart through venules and veins. These veins merge into the superior and inferior vena cava, delivering deoxygenated blood back to the right atrium, restarting the cycle.