The valves of the heart are structures which ensure blood flows in only one direction. They are composed of connective tissue and endocardium (the inner layer of the heart). Show There are four valves of the heart, which are divided into two categories:
In this article, we will look at the anatomy of these valves – their structure, function, and their clinical correlations By OpenStax College [CC BY 3.0], via Wikimedia Commons Fig 1 – The four valves of the heart, visible with the atria and great vessels removed. Atrioventricular ValvesThe atrioventricular valves are located between the atria and the ventricles. They close during the start of ventricular contraction (systole), producing the first heart sound. There are two AV valves:
The mitral and tricuspid valves are supported by the attachment of fibrous cords (chordae tendineae) to the free edges of the valve cusps. The chordae tendineae are, in turn, attached to papillary muscles, located on the interior surface of the ventricles – these muscles contract during ventricular systole to prevent prolapse of the valve leaflets into the atria. There are five papillary muscles in total. Three are located in the right ventricle, and support the tricuspid valve. The remaining two are located within the left ventricle, and act on the mitral valve. Fig 2 – The papillary muscles and inflow portion of the left ventricle. Semilunar ValvesThe semilunar valves are located between the ventricles and outflow vessels. They close at the beginning of ventricular relaxation (diastole), producing the second heart sounds. There are two semilunar valves:
The pulmonary and aortic valves have a similar structure. The sides of each valve leaflet are attached to the walls of the outflow vessel, which is slightly dilated to form a sinus. The free superior edge of each leaflet is thickened (the lunule), and is widest in the midline (the nodule). At the beginning of ventricular diastole, blood flows back towards the heart, filling the sinuses and pushing the valve cusps together. This closes the valve. Fig 3 – The aortic valve cusps, aortic sinuses, and the origin of the coronary arteries. Clinical Relevance: Aortic StenosisAortic stenosis refers to narrowing of the aortic valve, restricting the flow of blood leaving the heart. The main three causes are:
The classical triad seen in severe aortic stenosis is shortness of breath, syncope and angina. The increasing workload for the left ventricle can also result in left ventricular hypertrophy. Definitive treatment is surgical, and can be achieved via valve replacement or balloon valvuloplasty. Fig 4 – Aortic stenosis, secondary to rheumatic heart disease. The aorta has been removed to show thickened, fused aortic valve leaflets and opened coronary arteries from above. What type of valve is the pulmonic valve?In normal conditions, the pulmonic valve prevents regurgitation of deoxygenated blood from the pulmonary artery back to the right ventricle. It is a semilunar valve with 3 cusps, and it is located anterior, superior, and slightly to the left of the aortic valve.
What is the aortic and pulmonic valve?Two of the valves, the mitral and the tricuspid valves, move blood from the upper chambers of the heart (the atria) to the lower chambers of the heart (the ventricles). The other two valves, the aortic and pulmonary valves, move blood to the lungs and the rest of the body through the ventricles.
What type of valves are the aortic and pulmonic valves quizlet?These valves are considered entrance valves because they allow blood to enter the ventricles.
Is pulmonary valve bicuspid or tricuspid?Tricuspid valve: This valve has three leaflets. They allow blood to flow from the right atrium to the right ventricle. They also prevent blood from flowing backward from the right ventricle to the right atrium. Pulmonary valve: This valve also has three leaflets.
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