The heart is located in then ventral cavity, inside the thoracic cavity. To pump blood efficiently the heart needs valves that ensure a predominantly one-way flow. Blood flows through the heart in one direction - from atria to the ventricle and out the great arteries - leaving the superior aspect of the heart. This one-way traffic is enforced by four heart valves.
The four main valves in the heart are:
The two atrioventricular (AV) valves, the mitral valve (bicuspid valve), and the tricuspid valve, which are between the upper atria and the lower ventricles.
The two semilunar (SL) valves, the aortic valve and the pulmonary valve, which are in the arteries leaving the heart.
Each atrioventricular valves consist of a flap of connective tissue that is covered on both sides by endocardium and is devoid of blood vessels. The atrial surface of the flap, is smooth, the chord tendineae arise from its free margins and inferior surface. The atrioventricular (AV) valves regulate the openings between the atria and ventricles, the right AV tricuspid vale has three cups and the left AV bicuspid have has two.
The valves of the pulmonary trunk and aorta each consist of three nearly equally sized valves the semilunar cusps, which are formed by folds of endocardium. The semilunar valves regulate the flow of blood form the ventricles onto the great arteries. Aortic and pulmonary valves are of very similar structure to atrioventricular valves, but they do nor possess chord tendineae.
The texture of valves is as smooth as silk, thus blood particles and bacteria do not adhere to them.
Valves of the heart
