Morphology/Structure
The right atrioventricular valve is located at the orifice between the right atrium and ventricle. This corresponds to the region posterior at the fourth and fifth intercostal spaces. It's almost on the same plane as the left atrioventricular valve; however, the orifice of the right atrioventricular valve has a larger circumference (10–11 cm). It has three leaflets attached to a strong fibrocollagenous anulus. The anulus permits alterations to the conformation of the valve during the cardiac cycle.
The leaflets are named according to the regions of the orifice that they attach to and are called the superior, inferior, and septal leaflets. The leaflets have a fibrous core and are coated with endocardium. Each leaflet has a rough, clear, and basal zone. The rough zone corresponds to the region of the free margin where it provides an attachment for the chordae tendineae. It’s this region that comes into contact with the free margins of the adjacent leaflets when the valve is closed. The clear zone is smooth and more opaque and is the site of attachment of occasional chordae tendineae. The basal zone is thicker, due to increased collagen. It’s the region where the leaflets insert into the anulus.
Key Features/Anatomical Relations
The leaflets of the right atrioventricular valve are supported by and attached to chordae tendineae, which in turn attaches to the papillary muscles of the ventricular wall. In the right ventricle, there are three papillary muscles. These are the larger anterior and inferior (posterior) papillary muscles and a smaller septal papillary muscle. Each papillary muscle adjoins two leaflets.
-The anterosuperior muscle attaches to the anterior and posterior leaflets.
-The inferior (posterior) muscle adjoins to the posterior and septal leaflets.
-The septal muscle attaches to the septal and the anterior leaflets.
The right atrioventricular valve can be auscultated in the fourth intercostal space, at the left sternal edge.
Function
The right atrioventricular valve works in conjunction with the muscular contraction of the heart to permit unidirectional blood flow. They achieve this by altering their position, shape, and size.
During diastole, the anulus widens as the right ventricle relaxes. This causes the superior and inferior leaflets to “move away” from each other as they extend into the right ventricle. The septal leaflet is relatively fixed into position and leaflet movement is limited to the superior and inferior leaflets. The valve opens, and the leaflets extend into the left ventricle. As atrial pressure is greater than ventricular pressure blood flows towards the apex. The leaflets begin to come together again passively.
During ventricular systole, the anulus contracts slightly to assist with closing the valve. The papillary muscles contract which pulls the chordae tendineae and thus closes the valves by pulling the superior and inferior leaflets up towards the right atrium. This closes the valve and stops the leaflets from eversion.
List of Clinical Correlates
- Tricuspid valve stenosis
- Tricuspid valve regurgitation
- Infective endocarditis
- Rheumatic heart disease
- Ebstein’s anomaly
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Tricuspid Valve
It is the line of attachment of the tricuspid valve on its right aspect that divides the membranous septum into its atrioventricular and interventricular components, albeit that the proportions of the two components vary markedly from heart to heart.
