Describe the sequence of blood flow through the heart, including the chambers and valves.

• A. Right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary artery, lungs, pulmonary veins, left atrium, mitral valve, left ventricle, aortic valve, aorta.
• B. Right atrium, tricuspid valve, right ventricle, aortic valve, aorta, lungs.
• C. Right atrium, tricuspid valve, right ventricle, mitral valve, left ventricle, aorta.
• D. Right atrium, tricuspid valve, right ventricle, pulmonary valve, aorta.

Answer: (A)

Blood moves through the heart in one-way steps, with each chamber and valve guiding the flow through both the pulmonary and systemic circuits. Deoxygenated blood returning from the body enters the right atrium, passes through the tricuspid valve into the right ventricle, and then moves through the pulmonary valve into the pulmonary artery to the lungs for oxygenation. Oxygenated blood returns from the lungs via the pulmonary veins into the left atrium, flows through the mitral valve into the left ventricle, and is then pumped through the aortic valve into the aorta to supply the body. This sequence includes the full path through the lungs before reaching the left side and circulating systemically, with each valve acting as a one-way gate. The other sequences omit essential steps: they skip the pulmonary circulation, omit the left atrium, or jump to the aorta too early, so they don’t accurately describe the complete flow.