Which sequence correctly describes the pathway of blood flow through the heart?

• A. Right atrium — Tricuspid valve — Right ventricle — Pulmonic valve — Pulmonary artery — Lungs — Pulmonary veins — Left atrium — Bicuspid (Mitral) valve — Left ventricle — Aortic valve — Aorta
• B. Right atrium — Tricuspid valve — Right ventricle — Aortic valve — Aorta — Systemic circulation — Pulmonary veins — Left atrium — Mitral valve — Left ventricle — Pulmonary artery — Lungs
• C. Right atrium — Mitral valve — Left atrium — Tricuspid valve — Right ventricle — Pulmonary artery — Lungs — Pulmonary veins — Left ventricle — Aorta
• D. Right atrium — Pulmonic valve — Right ventricle — Tricuspid valve — Left atrium — Mitral valve — Left ventricle — Aortic valve — Aorta — Systemic circulation

Answer: (A)

The main idea is the one-way route that blood follows through the heart, driven by the heart’s valves and the connection to the lungs for oxygen exchange. Blood returning from the body without oxygen enters the right atrium via the superior and inferior vena cava. It then passes through the tricuspid valve into the right ventricle. From there it moves through the pulmonic valve into the pulmonary artery and travels to the lungs to drop off carbon dioxide and pick up oxygen. Oxygenated blood returns from the lungs through the pulmonary veins into the left atrium, then passes through the mitral valve into the left ventricle. Finally, it is pumped through the aortic valve into the aorta and out to the systemic circulation.

This sequence matches the flow described: right atrium → tricuspid valve → right ventricle → pulmonic valve → pulmonary artery → lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta. The other options disrupt the order of chambers, valves, or the direction of flow (for example, placing the aortic valve and systemic circulation before the pulmonary circuit, or linking the right atrium directly to the mitral valve, or inserting the pulmonic valve before the right ventricle), which makes them incorrect.