Left atrium receives the oxygenated blood returning from the lungs. Left ventricle has the thickest walls of all. It is from this chamber the blood is pumped out of the heart, into the aorta and out to the rest of the body. Since blood flow needs to be a one-way affair, there are valves at the entrance and exit of each ventricle. Each of the actual valves has it s own specific name though.
Tricuspid valve is the one located at the entrance of the right ventricle.
It prevents the blood from washing back into the right atrium. It gets its name from the three cusps or flaps that make up the valve. Pulmonary semilunar valve is located between the right ventricle and the pulmonary artery. Mitral valve is made of very heavy cusps and is located at the entrance of the left ventricle. This is a powerful valve that closes as the left ventricle begins each of its contractions to ensure the oxygenated blood doesn t re-enter the left atrium.