M01.05.018 The Valves of the Heart

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Learning Objective

By the end of this lesson, students should be able to:

Identify the four valves of the heart and classify them as atrioventricular or semilunar valves.
Describe the anatomical structure and supporting components of each valve.
Explain the functional role of valves during systole and diastole.
Correlate valve pathology, particularly aortic stenosis, with anatomical changes.

The heart valves are structures that ensure blood flows in one direction only. They are composed of connective tissue and endocardium (the inner layer of the heart).

There are four valves, divided into:

Atrioventricular (AV) valves: Tricuspid and Mitral
Semilunar valves: Pulmonary and Aortic

Atrioventricular (AV) Valves

The AV valves close during ventricular systole, producing the first heart sound (S1).

Valve	Location	Cusps	Support Structures
Tricuspid	Right atrium → Right ventricle	Three: anterior, septal, posterior	Chordae tendineae + 3 papillary muscles
Mitral (Bicuspid)	Left atrium → Left ventricle	Two: anterior, posterior	Chordae tendineae + 2 papillary muscles

Memory Tip: Think: Tricuspid → three points → right side, Mitral → two points → left side.

Semilunar Valves

The semilunar valves close at the start of ventricular diastole, producing the second heart sound (S2).

Valve	Location	Cusps	Clinical Feature
Pulmonary	Right ventricle → Pulmonary trunk	Three: left, right, anterior	Supplies pulmonary circulation
Aortic	Left ventricle → Ascending aorta	Three: right, left, posterior	Origin of coronary arteries → aortic sinuses

Key Features of Semilunar Valves

Sides of cusps attached to the vessel wall, forming a sinus
Free edge thickened = lunule
Center of lunule = nodule
Diastolic recoil closes the valve and fills the coronary arteries (aortic valve)