Which cardiac structure experiences the lowest pressure under normal conditions?

Which cardiac structure experiences the lowest pressure under normal conditions?

• A. Right atrium
• B. Left ventricle
• C. Aorta
• D. Pulmonary artery

Answer: (A)

The right atrium has the lowest pressure because it is the receiving chamber for systemic venous return and acts as a low-pressure reservoir. Its walls are thin and it operates at a very low pressure to accept blood before it moves into the right ventricle. In normal conditions, the right atrial pressure is about 2–6 mmHg (central venous pressure), whereas the left ventricle and aorta operate at high pressures (left ventricle systolic around 120 mmHg; aorta mean around 90 mmHg), and the pulmonary artery carries blood at a mean pressure of roughly 12–20 mmHg. Even the PA is higher than the RA, so the right atrium experiences the lowest pressure in the heart under normal conditions.

The right atrium has the lowest pressure because it is the receiving chamber for systemic venous return and acts as a low-pressure reservoir. Its walls are thin and it operates at a very low pressure to accept blood before it moves into the right ventricle. In normal conditions, the right atrial pressure is about 2–6 mmHg (central venous pressure), whereas the left ventricle and aorta operate at high pressures (left ventricle systolic around 120 mmHg; aorta mean around 90 mmHg), and the pulmonary artery carries blood at a mean pressure of roughly 12–20 mmHg. Even the PA is higher than the RA, so the right atrium experiences the lowest pressure in the heart under normal conditions.