What happens to the blood entering the left atrium?

The blood entering the left atrium comes from the lungs, where it has been oxygenated. From the left atrium, the blood does not get pumped directly into the lungs, nor is it mixed with deoxygenated blood since it is already rich in oxygen. The function of the left atrium is to receive oxygenated blood and then transfer it to the left ventricle.

Upon filling, the left atrium contracts and sends the oxygenated blood into the left ventricle. The left ventricle then contracts to pump this blood into the aorta, from which it is distributed throughout the body to supply tissues with oxygen and nutrients. This sequence is crucial for ensuring that oxygenated blood reaches systemic circulation effectively. Thus, sending the blood to the left ventricle for pumping to the body accurately describes this process.