Cardiac Valve Structure and Function

Cardiac valve structure and function describes the four one-way valves that keep blood moving in a single direction through the heart. The atrioventricular valves (tricuspid and mitral) separate the atria from the ventricles, and the semilunar valves (pulmonary and aortic) guard the outlets to the great arteries, opening and closing passively in response to the pressure differences of the cardiac cycle.

Definition

Cardiac valve structure and function refers to the anatomy of the heart's four valves and their supporting apparatus and to the way pressure differences across the cardiac cycle make them open and close to enforce unidirectional blood flow.

Scope

The topic covers the anatomy of the four valves and their supporting structures — leaflets or cusps, the annulus, and, for the atrioventricular valves, the chordae tendineae and papillary muscles — and the way pressure gradients drive their opening and closure during the cardiac cycle. It is descriptive anatomy and physiology and does not provide guidance on valvular disease management.

Core questions

• How are the atrioventricular and semilunar valves built?
• What supporting structures keep the atrioventricular valves competent?
• How do pressure changes in the cardiac cycle open and close the valves?
• How does valve function relate to the heart sounds?

Key concepts

• Atrioventricular valves (tricuspid, mitral)
• Semilunar valves (pulmonary, aortic)
• Leaflets, cusps, and the valve annulus
• Chordae tendineae and papillary muscles
• Pressure gradients and passive valve motion
• Relationship of valve closure to heart sounds

Mechanisms

The valves open and close passively according to the pressure on either side. As the ventricles fill, the atrioventricular valves are open; when ventricular pressure rises in systole they close, and the chordae tendineae anchored to the papillary muscles prevent the leaflets from everting into the atria. When ventricular pressure exceeds that in the aorta and pulmonary artery, the semilunar valves open and blood is ejected; as the ventricles relax and pressure falls, these valves close to prevent backflow. The closure of the atrioventricular valves produces the first heart sound and the closure of the semilunar valves the second (Anderson, 2000).

Clinical relevance

Normal valve anatomy and the pressure dynamics that govern opening and closure are the reference frame for understanding stenosis and regurgitation and for interpreting murmurs and heart sounds. This topic describes the normal valves and is educational; it is not a basis for individual diagnosis or treatment, which are addressed in clinical guidelines (Vahanian et al., 2022; Bonow et al., 2008).

Evidence & guidelines

Valve anatomy is grounded in cardiac-morphology references (Anderson, 2000; Anderson et al., 2013), and the clinical management of valvular disease is addressed in current guidelines (Vahanian et al., 2022; Bonow et al., 2008). This topic itself is a descriptive reference, not a guideline.

History

The gross structure of the cardiac valves has been known since early anatomical study, but understanding of the mitral and tricuspid apparatus as integrated functional units — leaflets, annulus, chordae, and papillary muscles working together — was refined through twentieth-century surgical anatomy, informing both diagnosis and repair.

Key figures

• Robert H. Anderson
• Alain Carpentier

Seminal works

• anderson-2000-aortic-root

Frequently asked questions

What keeps the atrioventricular valves from turning inside out during contraction?

The chordae tendineae connect the valve leaflets to the papillary muscles of the ventricular wall, holding the leaflets in place so they do not prolapse into the atria when ventricular pressure rises.

What produces the two main heart sounds?

The first heart sound comes from closure of the atrioventricular (mitral and tricuspid) valves at the start of systole, and the second from closure of the semilunar (aortic and pulmonary) valves at the end of systole.