The deoxygenated blood returns to the heart through the inferior and superior ____. This blood enters into the ____. The right atrium ____ forcing blood through the ____ into the ____. On the opposite side of the heart, oxygentated blood returns to the heart through the ____ into the ____. This blood enters the ____ through the ____. This stage is called ____, which means the heart relaxes and fills with blood.

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