Anatomy and Physiology of the Heart - Part 3

The heart consists of four key valves:

 - Those between the Atrium and the Ventricles - On the right side the Tricuspid Valve (3 cusps), and on the left side Mitral Valve (2 cusps).

- Those between the Ventricles and out of the heart, commonly known as the Semilunar Valves (3 cusps) - On the right side the Pulmonary Valve and on the left side Aortic Valve.

Atrioventricular Valves:

The opening of the Atrioventricular Valves allows the flow of blood from the Atrium to the Ventricles, this happens when the Ventricle pressure is lower than the Atrial pressure.

• This occurs when the Ventricles, Papillary muscles, and the Chordae Tendineae are relaxed.

The closing of the Atrioventricular Valves prevents the back-flow of blood to the Atrium during Ventricular contraction. This occurs when the Ventricular pressure is greater than the Atrial pressure, causing the leaves in the valve to close.

• This occurs when the Chordae Tendineae are stretched, the Papillary muscles contract and pull the chordae (cables) that prevent the cusps from inverting.

Semilunar Valves:

Semilunar Valves open when the Ventricles are contracted to allow blood to flow to the Lungs (right side) and Aorta (left side).

• The Semilunar Valves are closed during Ventricular relaxation to prevent back-flow of blood to the Ventricles. This occurs when the blood begins to return to the Ventricles as a result of vascular resistance and the filling of the Valve leaves until they are closed.