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A heart valve normally allows blood to flow through it in only one direction. There are four in a mammalian heart and they determine the pathway of blood flow through the heart. A heart valve opens or closes depending on the different pressures on each side of it.[1][2][3] The four valves in the heart are:[4] The two atrioventricular (AV) valves, which are between the atria and the ventricles, are the mitral valve and the tricuspid valve. The two semilunar (SL) valves, which are in the arteries leaving the heart, are the aortic valve and the pulmonary valve. A form of heart disease occurs when a valve malfunctions and allows some blood to flow in the wrong direction. This is called regurgitation. Contents [hide] 1 Atrioventricular valves 1.1 Mitral valve 1.2 Tricuspid valve 2 Semilunar valves 2.1 Aortic valve 2.2 Pulmonary valve 3 See also 4 Notes 5 External links [edit]Atrioventricular valves

This is an explanation of the echocardiogram above. MV: Mitral valve, TV: Tricuspid valve, AV: Aortic valve, Septum: Interventricular septum. Continuous lines demarcate septum and free wall seen in echocardiogram, dotted line is a suggestion of where the free wall of the right ventricle should be. The red line represents where the upper left loop in the echocardiogram transects the 3D-loop, the blue line represents the lower loop.

An artificial heart valve may be used to surgically replace a patient's damaged valve. These are small valves that prevent backflow from the ventricles into the atrium during systole. They are anchored to the wall of the ventricle by chordae tendineae, which prevent the valve from inverting. The chordae tendineae are attached to papillary muscles that cause tension to better hold the valve. Together, the papillary muscles and the chordae tendineae are known as the subvalvular apparatus. The function of the subvalvular apparatus is to keep the valves from prolapsing into the atria when they close. The subvalvular apparatus have no effect on the opening and closure of the valves, however. This is caused entirely by the pressure gradient across the valve. The closure of the AV valves is heard as the first heart sound (S1). [edit]Mitral valve Main article: mitral valve Also known as the "bicuspid valve" contains two flaps. The mitral valve gets its name from the resemblance to a bishop's mitre (a type of hat). It allows the blood to flow from the left atrium into the left ventricle. It is on the left side of the heart and has two cusps. A common complication of rheumatic fever is thickening and stenosis of the mitral valve. [edit]Tricuspid valve Main article: tricuspid valve The tricuspid valve is the three-flapped valve on the right side of the heart, between the right atrium and the right ventricle which stops the backflow of blood between the two. It has three cusps. [edit]Semilunar valves

These are located at the base of both the pulmonary trunk (pulmonary artery) and the aorta, the two arteries taking blood out of the ventricles. These valves permit blood to be forced into the arteries, but prevent backflow of blood from the arteries into the ventricles. These valves do not have chordae tendineae, and are more similar to valves in veins than atrioventricular valves. [edit]Aortic valve Main article: aortic valve The aortic valve lies between the left ventricle and the aorta. The aortic valve has three cusps. During ventricular systole, pressure rises in the left ventricle. When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to close. The closure of the aortic valve contributes the A2 component of the second heart sound (S2). The most common congenital abnormality of the heart is the bicuspid aortic valve. In this condition, instead of three cusps, the aortic valve has two cusps. This condition is often undiagnosed until the person develops calcific aortic stenosis. Aortic stenosis occurs in this condition usually in patients in their 40s or 50s, an average of over 10 years earlier than in people with normal aortic valves. [edit]Pulmonary valve Main article: pulmonary valve The pulmonary valve (sometimes referred to as the pulmonic valve) is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. Similar to the aortic valve, the pulmonary valve opens in ventricular systole, when the pressure in the right ventricle rises above the pressure in the pulmonary artery. At the end of ventricular systole, when the pressure in the right ventricle falls rapidly, the pressure in the pulmonary artery will close the pulmonary valve. The closure of the pulmonary valve contributes the P2 component of the second heart sound (S2). The right heart is a low-pressure system, so the P2 component of the second heart sound is usually softer than the A2 component of the second heart sound. However, it is physiologically normal in some young people to hear both components separated during inhalation. [edit]See also