1.10.2 Atrioventricular Valve Definition

Atrioventricular Valve Definition is a description of the pair of cardiac valves, the mitral and tricuspid valves, that separate the atria from the ventricles and regulate the passage of blood from each atrium into its corresponding ventricle. These valves open during diastole to permit ventricular filling and close at the onset of ventricular systole to prevent the backward flow of blood into the atria, functioning as pressure-actuated, one-way gates positioned at the atrioventricular junctions.

The Two Atrioventricular Valves

Each side of the heart contains one atrioventricular valve, distinguished by the number of leaflets it possesses.

Mitral Valve

The mitral valve, also called the bicuspid valve, lies between the left atrium and left ventricle and is composed of two leaflets, an anterior and a posterior leaflet.

Tricuspid Valve

The tricuspid valve lies between the right atrium and right ventricle and is composed of three leaflets, typically described as anterior, posterior, and septal.

Supporting Structures

Unlike the semilunar valves, atrioventricular valves are anchored by an additional apparatus that prevents them from being pushed backward into the atria during ventricular contraction.

Chordae Tendineae

Chordae tendineae are thin, fibrous cords that connect the free edges of the valve leaflets to the papillary muscles within the ventricular wall, restraining leaflet motion and preventing prolapse.

Papillary Muscles

Papillary muscles are projections of ventricular myocardium that contract in synchrony with the surrounding ventricular wall, applying tension to the chordae tendineae precisely when ventricular pressure rises, thereby holding the valve leaflets securely closed during systole.

Functional Cycle

The atrioventricular valves open and close in direct response to the pressure gradient between the atria and ventricles.

Opening Phase

During diastole, as the ventricles relax and their pressure falls below atrial pressure, the atrioventricular valves open, permitting the rapid filling, diastasis, and atrial systole stages of ventricular filling.

Closing Phase

At the onset of ventricular systole, rising ventricular pressure exceeds atrial pressure, forcing the valve leaflets shut. This closure, stabilized by the chordae tendineae and papillary muscles, produces the first heart sound (S1).

Diagrammatic Summary

Clinical Relevance

Dysfunction of the atrioventricular valves or their supporting apparatus, including leaflet stenosis, chordal rupture, or papillary muscle dysfunction, can result in either restricted forward flow or regurgitant backward flow, both of which impair the efficiency of ventricular filling and ejection. Recognition of the normal structure and closing mechanism of these valves is essential to understanding conditions such as mitral valve prolapse and tricuspid regurgitation.