The heart valves are structures that regulate the flow of blood within the heart. It is appendages of fabric essentially fibrous, coated by endocardium, which control the passage of blood through the orifices which connect atria with the ventricles and the ventricles with the aorta or pulmonary artery .
The four heart valves are:
- tricuspid valve ;
- bicuspid valve or mitral ;
- aortic semilunar valve with three cusps ;
- Pulmonary semilunar valve with three cusps .
The opening and closing of the valves is entirely bound to intracardiac pressure changes. In fact there is no control nervous or muscular activity of the valves, which are then simply pushes the blood flow itself. The main task of the heart valves is to prevent, ensuring effective resistance and passive, the backflow of blood to the atria during the systolic phase or "ventricular contraction" (tricuspid valves and bicuspid) or towards the ventricles during the diastolic phase or " ventricular relaxation "(semilunar valves).
The heart valves are often subject to various pathologies , which may reduce efficiency. Sometimes, intervention shall be replacement surgery with cardiac valve prosthesis .
The tricuspid valve
The tricuspid valve (also known as the tricuspid valve ) is a valve of an oval shape (diameter of 12 mm ) which regulates the blood flow between the ' atrium , right and the right ventricle .
It owes its name to which it is composed of three layers, which are called cusps . Each is characterized by an axial face, a face wall, a margin adherent (which makes contact with the orifice) and a free margin. Fibrous structures (called chordae tendineae ) connecting the papillary muscles to the free margins of the valve leaflets ensuring their coaptation during systole. The outbreak of auscultation of the tricuspid valve is located in the fourth intercostal space marginosternale left and right.
The mitral valve
The mitral valve , so named for its likeness to the ceremonial headdress (also known as the bicuspid valve ) has a diameter of over 30 mm , regulates blood flow between the ' atrium and left ventricle, the left and has an orifice of 4-6 cm 2 . According to the latest trends, we now prefer to call the complex system such as mitral valvular mitral apparatus rather than as mitral valve, as is the complex interaction between ring valve, the valve leaflets, chordae, papillary muscles and left ventricle to operate properly the valve mechanism. As the tricuspid valve, has a slightly oval shape. Unlike the tricuspid valve, the mitral valve has two cusps: a, larger, mail forward and medially, which corresponds to the front wall and the left of the septum, view the orifice and is called the aortic cusp front or aortic ; the other, smaller, post back and laterally, which corresponds to the rear wall of the left ventricle and is called cusp rear . The anterior leaflet of the mitral valve is always smooth. The papillary muscles are two and are located close to the apex of the left ventricle: one is called the front and is forward and sideways, the other is called back and is on the right and sideways. The chordae tendineae are inserted on the valve cusps in order to optimize the distribution of stress during systole  (video) . The outbreak of the mitral auscultation is located in an area called the ight of the tip, which is the apex of the heart and appreciate the 5 th intercostal space an inch inside the midclavicular line.
The aortic semilunar valve
The aortic semilunar valve or aortic valve (20 mm diameter) regulates blood flow from the heart to the circulatory system.
Located at the orifice that connects the aorta to the left ventricle, the valve has a structure to swallow's nest. Erroneously is considered as the only valve the sum of the three flaps, each flap in fact constitutes a valve and its offset position ensures the closure of the jar, preventing the reflux of blood in the ventricle. They have a characteristic crescent shape, hence the name. The three flaps have a fibrous thickening, said nodule of Aranzio , which, in closed position, makes it more complete closure of the valve. The outbreak of auscultation is the second right intercostal space near sternum.
The pulmonary semilunar valve
The pulmonary semilunar valve and pulmonary valve (20 mm diameter) regulates blood flow from the heart to the pulmonary circulation . On the number of flaps that comprise the distinction that is made to the aortic semilunar valve. The fibrous thickening which makes it more complete closure takes the name of the nodule of Morgagni. The outbreak of lung auscultation of the lunate anatomically corresponds to the outbreak and is located at the second left intercostal space near sternum.