Our heart has four chambers and four valves. The valves are named as mitral valve, tricuspid valve, aortic valve and pulmonary valve. They prevent backflow of blood and allow the functioning of the heart and circulatory system in perfect harmony.
Mitral valve is the valve between the left sided upper and lower chambers of the heart, between the left atrium and left ventricle. Its shape resembles the headwear of a bishop (mitre) and hence the name. Mitral valve has two leaflets and is called a bicuspid valve. It closes when the left ventricle contracts, so that blood from the left ventricle does not flow back into the left atrium. Tips of the valve leaflets are held taut by string like structures (chordae tendinae) which connect the valve to small muscles in the left ventricle (papillary muscles).
Tricuspid valve is between the right upper and lower chambers – right atrium and right ventricle. It has three leaflets and hence the name. It closes when the right ventricle contracts thereby preventing leakage of blood from the right ventricle into the right atrium. Like the mitral valve, it is also kept taut by chordae tendinae and papillary muscles. Tricuspid valve has the largest orifice area among the four heart valves.
Aortic valve lies between the left ventricle and the aorta, the largest blood vessel supplying blood to the whole body. It has three semilunar cusps and it is mentioned as a semilunar valve. Aortic valve closes when the left ventricle relaxes after a contraction. Hence the blood pumped into the aorta when the ventricle contracts does not flow back into the left ventricle. This enables the forward flow of blood into the aorta and its branches, reaching all parts of the body, where it is required for various functions.
Pulmonary valve is between the right ventricle and the pulmonary artery. Pulmonary artery is a large blood vessel which carries deoxygenated blood to the lungs for oxygenation. Pulmonary valve closes when the right ventricle relaxes after contraction, preventing backflow of blood from the pulmonary artery to the right ventricle. Like the aortic valve, pulmonary valve also has three semilunar cusps and is known as a semilunar valve.