Heart valve chambers are lined with endocardium. Heart valves separate the atria from the ventricles, or the ventricles from a blood vessel. Heart valves are situated around the fibrous rings of the cardiac skeleton. The valves incorporate leaflets or cusps, which are pushed open to allow blood flow and which then close together to seal and prevent backflow. The mitral valve has two cusps, whereas the others have three. There are nodules at the tips of the cusps that make the seal tighter. The pulmonary valve has left, right, and anterior cusps. The aortic valve has left, right, and posterior cusps. The
Lateral ventricles floor is formed by the fimbria hippocampi (from which the fornix emerges), and then, more anteriorly, by the hippocampus itself. As with the posterior horn, the remainder of the boundary - in this case the lateral side of the floor - is directly in contact with the white matter of the surrounding lobe. During development, pressure from exterior structures causes a number of concave bulges to form within the lateral ventricles, which can be extremely variable in their degree of development; in some individuals they are ill-defined, while in others they can be prominent: Between the inferior horn and the