The mitral valve has two leaflets, or flaps, that open when the heart relaxes (diastole) and close when it contracts (systole). The base of each leaflet is attached to the heart muscle—the myocardium—by strong, flexible cords called the chordae tendineae, which control the opening and closing of the mitral valve. The chordae are thin and white. Their appearance is often compared to the strings of a parachute.

The chordae attach to the papillary muscles, a group of muscle fibers in the myocardium. These muscle fibers are located inside the lower left chamber (left ventricle) of the heart.