Which heart chamber forms the base of the heart?

Which heart chamber forms the base of the heart?

• A. Left atrium
• B. Right atrium
• C. Left ventricle
• D. Right ventricle

Answer: (A)

The broad, posterior surface of the heart—the base—is formed primarily by the atria. In particular, the left atrium makes up the main portion of the base, facing posteriorly toward the vertebral column. The right atrium contributes only a small part of the base and helps form the right border, while the left ventricle shapes the apex and much of the anterior surface. The left atrium also receives the four pulmonary veins, and its posterior wall lies close to structures like the esophagus. So the left atrium is the best answer because it defines the base of the heart.

The broad, posterior surface of the heart—the base—is formed primarily by the atria. In particular, the left atrium makes up the main portion of the base, facing posteriorly toward the vertebral column. The right atrium contributes only a small part of the base and helps form the right border, while the left ventricle shapes the apex and much of the anterior surface. The left atrium also receives the four pulmonary veins, and its posterior wall lies close to structures like the esophagus. So the left atrium is the best answer because it defines the base of the heart.