Left Ventricle:The lower left chamber of the heart. During the normal cardiac cycle, the left ventricle receives oxygenated blood through the mitral valve from the left atrium as it contracts. At the same time, the aortic valve leading to the aorta is closed, allowing the ventricle to fill with blood. Once both ventricles are full, they contract. As the left ventricle contracts, the mitral valve closes and the aortic valve opens. The closure of the mitral valve prevents blood from returning to the left atrium, and the opening of the aortic valve allows the blood to flow into the aorta and from there throughout the body.
The left and right ventricles contract simultaneously; however, because the left ventricle is thicker than the right, it produces a higher presure than the right when contracting. This higher pressure is necessary to pump the oxygenated blood throughout the body.