Where does blood first enter the heart?

Where does blood first enter the heart?

• A. Right Atrium
• B. Left Atrium
• C. Right Ventricle
• D. Left Ventricle

Answer: (A)

Blood returning from the body first arrives at the heart into the right atrium. Venous blood from the superior and inferior vena cavae (and the coronary sinus draining the heart muscle) enters this chamber. From the right atrium, blood moves through the tricuspid valve into the right ventricle, which then pumps it to the lungs for oxygenation. Only after oxygenated blood returns from the lungs does it enter the left atrium, pass into the left ventricle, and be distributed to the body. So the initial entry point for blood into the heart is the right atrium.

Blood returning from the body first arrives at the heart into the right atrium. Venous blood from the superior and inferior vena cavae (and the coronary sinus draining the heart muscle) enters this chamber. From the right atrium, blood moves through the tricuspid valve into the right ventricle, which then pumps it to the lungs for oxygenation. Only after oxygenated blood returns from the lungs does it enter the left atrium, pass into the left ventricle, and be distributed to the body. So the initial entry point for blood into the heart is the right atrium.