Now we'll move on to look at the two ventricles and their inlet valves. To see them clearly, we'll look at a heart in which the right and left atrium have been removed, leaving just the two ventricles. Here's the right ventricle, seen from the right side, here's the left ventricle, seen from the front.
Going round to the back, this is the right ventricle, this is the left one. They're separated by the interventricular septum, which is here. We're looking forwards into the wide-open atrio-ventricular valves, the tricuspid on the right, the mitral on the left.
On the right side, blood passes downwards and forwards to fill the right ventricle in diastole, then in systole it passes upwards and to the left into the pulmonary trunk, passing through the pulmonary valve, which is here.
On the left, blood also passes downwards and forwards to fill the ventricle, then gets turned completely around in systole, passing upwards and backwards into the aorta. It passes through the aortic valve, which is out of sight, here.