Describe and explain how blood in the right ventricle travels to the left atrium.

The muscle of the right ventricle contracts. This forces the {right atrio-ventricular/tricuspid} valve to close and the {right semi-lunar/pulmonary} valve to open. The blood is pumped through the pulmonary artery into the lungs where it becomes oxygenated. The blood then leaves the lungs and passes through the pulmonary vein as it re-enters the heart in the left atrium.