What is the correct sequence of blood flow through the heart from the vena cava to the aorta?

• A. Vena cava → right atrium → tricuspid valve → right ventricle → aortic valve → aorta.
• B. Vena cava → right atrium → mitral valve → left ventricle → aortic valve → aorta.
• C. Vena cava → right atrium → tricuspid valve → right ventricle → pulmonic valve → pulmonary artery → lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic valve → aorta.
• D. Vena cava → right atrium → tricuspid valve → left ventricle → pulmonary valve → lungs.

Answer: (C)

Blood travels in a single loop through the heart: from the vena cava the blood enters the right atrium, moves through the tricuspid valve into the right ventricle, then passes the pulmonic valve into the pulmonary artery to the lungs for oxygenation. After returning from the lungs via the pulmonary veins, it enters the left atrium, goes 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 is essential because the right side handles deoxygenated blood and the left side handles oxygenated blood, with the lungs providing gas exchange before systemic circulation.

Other sequences omit the pulmonary circulation or place valves incorrectly (for example, skipping the lungs or moving blood from the right atrium to the left ventricle), which isn’t how blood actually flows through the heart.