In the pathway of the flow of blood through the heart, oxygenated blood returns from the lungs and enters the

oright atrium
oright ventricle.
left atrium
left ventricle.

Left atrium

Explanation:

The human heart is one of the most important organs in the body. It sustains life through a pumping mechanism. It also aids in the body's circulatory system.

It is important to know that there are four chambers of the heart: right atrium, right ventricle, left atrium and left ventricle. These chambers are divided by the septum.

When the blood enters the heart, it passes through the inferior and superior vena cava, then it goes to the right atrium. Upon contraction of the atrium, the blood passes through the tricuspid valve and goes to the right ventricle. The tricuspid valve closes when its full in to prevent the backward flow of blood. This allows the blood to proceed through the pulmonic valve going to the pulmonary artery, then to the lungs. The blood becomes oxygenated here. The oxygen-rich blood empties into the left atrium, through the pulmonary veins. Upon the contraction of the atrium, the blood flows through the open mitral valve towards the left ventricle.

Thus, the answer is left atrium.

a progressive heart disease that affects pumping action of the heart muscles.

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