Q.Distinguish between Mitral valve and Semi-lunar valve.

The mitral (bicuspid) valve sits between the left atrium and left ventricle and has two flaps, while the semilunar valves sit at the openings of the ventricles into the great arteries (aorta and pulmonary artery) and have three pocket-like cusps; both prevent backflow of blood, but in different locations and with different structures.

Mitral valve (bicuspid valve):

• Location: guards the opening between the left atrium and the left ventricle.

• Structure: has two flap-like cusps (hence "bicuspid").

• Support: anchored to papillary muscles of the ventricle wall by tough, string-like chordae tendineae, which prevent the valve flaps from being pushed back (everting) into the atrium during forceful ventricular contraction.

• Function: opens to let oxygenated blood flow from the left atrium into the left ventricle during ventricular relaxation (diastole), and closes tightly during ventricular contraction (systole) to prevent blood from flowing backward into the atrium.

Semilunar valves (aortic and pulmonary):

• Location: one guards the opening from the left ventricle into the aorta (aortic semilunar valve), and the other guards the opening from the right ventricle into the pulmonary artery (pulmonary semilunar valve).

• Structure: each has three pocket- or half-moon- (crescent-) shaped cusps, and unlike the mitral/tricuspid valves, they are not attached to chordae tendineae or papillary muscles.

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