serratus anterior attaches to the chordae tendineae to hold the valves in place.
serratus anterior attaches to the chordae tendineae to hold the valves in place.
what muscle attach to the chordae tendineae to hold the valves in place?
serratus anterior
the first heart sound, or s, forms the "lub" of "lub-dub" and is composed of components m (mitral valve closure) and t (tricuspid valve closure). normally m precedes t slightly. it is caused by the closure of the atrioventricular valves, i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole. when the ventricles begin to contract, so do the papillary muscles in each ventricle. the papillary muscles are attached to the cusps or leaflets of the tricuspid and mitral valves via chordae tendineae (heart strings). when the papillary muscles contract, the chordae tendineae become tense and thereby prevent the backflow of blood into the lower pressure environment of the atria. the chordae tendineae act a bit like the strings on a parachute, and allow the leaflets of the valve to balloon up into the atria slightly, but not so much as to evert the cusp edges and allow back flow of blood. it is the pressure created from ventricular contraction that closes the valve, not the papillary muscles themselves. the contraction of the ventricle begins just prior to av valves closing and prior to the semilunar valves opening. the sudden tensing of the chordae tendineae and the squeezing of the ventricles against closed semilunar valves, sends blood rushing back toward the atria, and the parachute-like valves catch the rush of blood in their leaflets causing the valve to snap shut. the s1 sound results from reverberation within the blood associated with the sudden block of flow reversal by the valves. the delay of t1 even more than normally causes the split s1 which is heard in a right bundle branch blockage.
heart sounds
each leaflet is composed of three layers of tissue: the "atrialis", "fibrosa", and "spongiosa". patients with classic mitral valve prolapse have excess connective tissue that thickens the spongiosa and separates collagen bundles in the fibrosa. this is due to an excess of dermatan sulfate, a glycosaminoglycan. this weakens the leaflets and adjacent tissue, resulting in increased leaflet area and elongation of the chordae tendineae. elongation of the chordae tendineae often causes rupture, commonly to the chordae attached to the posterior leaflet. advanced lesions—also commonly involving the posterior leaflet—lead to leaflet folding, inversion, and displacement toward the left atrium.









































section::::genetics.
mitral valve prolapse