Deoxygenated blood from the upper part of the body returns to the right atrium (RA) via the superior vena cava. On the other hand, deoxygenated blood from the lower portion of the body returns to the RA via the inferior vena cava. When the RA is full, it contracts which builds up the pressure and opens the tricuspid valve. Blood transfers from the RA into the right ventricle (RV). When the RV is filled, the walls of the ventricle begin to contract and the pressure within the RV rises. The increased pressure closes the tricuspid valve and blood is pumped into the pulmonary artery through the pulmonic valve.

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