Starting from the right atrium, which is the correct sequence of blood flow through the heart?

• A. Right atrium -> Right ventricle via tricuspid -> Pulmonary trunk via pulmonary valve -> Lungs -> Left atrium via pulmonary veins -> Left ventricle via mitral valve -> Aorta.
• B. Right atrium -> Right ventricle
• C. Right atrium -> Pulmonary artery -> Lungs -> Left atrium
• D. Right atrium -> Left atrium via pulmonary veins -> Right ventricle

Answer: (A)

Blood moves through the heart in one complete circuit: it starts with deoxygenated blood returning to the right atrium, then goes through a valve into the right ventricle, which then pushes it through the pulmonary valve into the pulmonary trunk and onward to the lungs for oxygenation. After picking up oxygen, the blood returns to the heart via the pulmonary veins into the left atrium, passes through the mitral valve into the left ventricle, and is then pumped through the aortic valve into the aorta to supply the body. The depicted sequence matches this path, including passing through the right ventricle before reaching the lungs and then moving to the left heart for systemic circulation. Other options skip steps, place vessels out of order, or imply direct atrial transfer that doesn’t occur in anatomy (such as moving directly from the right atrium to the left atrium via the pulmonary veins).