Right sideBlood enters the heart through two large veins, the INFERIOR and superior vena cava, emptying oxygen-poor blood from the body into the right atrium.As the atrium CONTRACTS, blood flows from your right atrium into your right VENTRICLE through the open tricuspid valve.When the ventricle is full, the tricuspid valve shuts. This PREVENTS blood from flowing backward into the atria while the ventricle contracts.As the ventricle contracts, blood leaves the heart through the PULMONIC valve, into the pulmonary artery and to the lungs where it is oxygenated.Left sideThe pulmonary vein empties oxygen-rich blood from the lungs into the left atrium.As the atrium contracts, blood flows from your left atrium into your left ventricle through the open mitral valve.When the ventricle is full, the mitral valve shuts. This prevents blood from flowing backward into the atrium while the ventricle contracts.As the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta and to the body.