The human heart functions as a powerful, continuous pump, circulating blood throughout the body. This efficiency depends on a complex system of one-way valves that ensure blood moves forward and never backward. The tendinous chords, formally known as the chordae tendineae, are small, fibrous restraints integral to maintaining the functional integrity of the heart’s valves, which is necessary for efficient blood circulation.
Anatomy and Composition
The tendinous chords are thin, cord-like structures situated in the lower chambers of the heart, the ventricles. These cords connect the flaps, or cusps, of the two atrioventricular (AV) valves: the tricuspid valve on the right side and the mitral valve on the left side.
At one end, the chordae attach directly to the edges and ventricular surface of the valve leaflets. At their opposite end, they anchor firmly to small, cone-shaped muscles that project from the ventricular walls, called the papillary muscles. The primary material composition of the chordae is collagenous fibers, which provide exceptional tensile strength to withstand the high internal pressures generated by the contracting heart.
Mechanical Role in Valve Function
The primary function of the tendinous chords is to provide structural support to the AV valve leaflets during ventricular contraction, known as systole. When the ventricles contract, the rising pressure pushes the valve cusps closed, preventing blood from flowing backward into the atria. Without restraint, this powerful pressure would force the valve leaflets to flip completely backward, or prolapse, into the atria.
The chordae counteract this prolapse through a coordinated mechanical action involving the papillary muscles. As the ventricular muscle wall contracts, the attached papillary muscles also contract slightly. This contraction maintains a precise tension on the tendinous chords. The taut chords hold the closed valve leaflets firmly in place, ensuring the seal between the atrium and the ventricle remains intact. This precise tethering action preserves unidirectional blood flow.
Consequences of Structural Failure
When the tendinous chords are compromised, their ability to restrain the valve leaflets is lost, leading to valve regurgitation, or insufficiency. A rupture or excessive lengthening of chords allows the corresponding valve leaflet to prolapse back into the atrium during ventricular systole. This mechanical failure causes blood intended for circulation to leak backward into the atrium, resulting in inefficient circulation.
The causes of chordal failure include degenerative diseases that weaken the tissue over time. Acute rupture can occur as a complication of severe events, such as a heart attack, which damages the supporting papillary muscles. Bacterial infections of the heart lining, known as infective endocarditis, can also destroy the chordae. Severe regurgitation forces the heart to work harder, leading to reduced efficiency and potentially resulting in congestive heart failure.