8.2. Right Ventricle
Note: the right atrium is connected to the right ventricle by the right atrioventricular orifice. This orifice has to be closed off at a specific point during each cardiac cycle by the tricuspid valve (also called the right atrioventricular valve) in order to prevent blood from flowing back into the atrium.
The tricuspid valve
The tricuspid valve has three cusps: an anterior cusp, a posterior cusp and a septal cusp. These cusps come together to block the atrioventricular orifice. These cusps are connected to fibrous chords called chordae tendineae. The chordae tendineae are themselves attached to papillary muscles that are part of the muscular wall of the ventricle. The papillary muscles are also classed as anterior, posterior or septal respectively. At this stage it is important to note that when the papillary muscles contract, the chordae tendineae become taut. This prevents the cusps from inverting (turning inside out). But note that, when the papillary muscles contract, they are not forcefully closing the cusps - this is actually done by the increase in ventricular pressure during ventricular systole (more on this later).
These are the ridged muscle fibres that project from the inner surface of the ventricle. These are not as prominent in the right ventricle as the left ventricle, because the right ventricle requires a smaller contractile force to push blood the short distance to the lungs.
Moderator band (also called septomarginal trabecula)
This is only present in the right ventricle, this muscle bundle also contains the right branches of the atrioventricular bundle, which is part of the heart's electrical conduction system. The moderator band acts as a shortcut for the action potential heading to the anterior papillary muscle, ensuring that this muscle contracts at the same time as the others. This ensures that the three cusps of the tricuspid valve are pulled taut together, and thus form a tight 'blood-proof' seal.
The area of the ventricular wall where the pulmonary trunk begins to form.