How many veins empty deoxygenated blood into the right atrium?

The correct answer is three because the right atrium receives deoxygenated blood from three major veins: the superior vena cava, the inferior vena cava, and the coronary sinus. The superior vena cava drains blood from the upper half of the body, while the inferior vena cava drains blood from the lower half. The coronary sinus collects blood from the heart muscle itself, which is crucial for maintaining proper cardiac function. Together, these three veins ensure that the right atrium effectively gathers all the deoxygenated blood before it is pumped into the right ventricle and then to the lungs for oxygenation.

This anatomical understanding is essential for interpreting the normal flow of blood in the heart and can be significant when assessing various cardiac conditions in echocardiography.