The heart has four chambers and valves that work together to pump blood around the body. Explain how the structure of the heart allows it to pump deoxygenated blood to the lungs and oxygenated blood to the rest of the body at the same time.

The heart is divided into a right and a left side by the interventricular septum, so oxygenated and deoxygenated blood never mix. The right atrium receives deoxygenated blood from the body, which passes through the tricuspid valve into the right ventricle. Contraction of the right ventricle forces the blood through the pulmonary valve into the pulmonary artery, carrying it to the lungs for oxygenation. Meanwhile, the left atrium receives oxygenated blood from the lungs, which flows through the mitral valve into the left ventricle. The left ventricle has a much thicker muscular wall than the right ventricle, allowing it to generate higher pressure; when it contracts it pushes blood through the aortic valve into the aorta, distributing oxygenated blood to the rest of the body. The atrioventricular and semilunar valves prevent back‑flow, ensuring unidirectional flow through the heart.