Functions of Valves operating mechanism

Answer 1

The functional anatomical status of tricuspid and mitral valves is a normally open state, and the status of pulmonary and aortic valves is a normally closed state. This is their functional status when they are not actuated by the central nervous system. The specialized nervous areas of the heart of the CNS individually coordinate each side of the heart. Since the mechanism of the left heart is similar and (in normal conditions) synchronized to the right heart, I describe the mechanism of the right side of the heart having regard to its determinant role within the cardiac function. In the diastole phase, the blood flow running into the right ventricle (through normally open tricuspid valve) stimulates the sympathetic nerve fibers of the right ventricle, and the normally closed pulmonary valve stops the blood flow. In the systole phase when the transmural pressure of the right atrium and ventricle becomes equal to the transmural central venous pressure, there occurs the maximal stimulation of specialized nervous area of the right side of the heart of the central nervous system. The specialized nervous area of the CNS sends back to the right side of the heart (via parasympathetic nerve fibers) action potentials to contract the right ventricle, actuating simultaneously both closing tricuspid valve and opening pulmonary valve, and the blood is pumped into the pulmonary trunk. The return to the normally open state of the tricuspid valve takes place passively during ventricular diastole by means of chordae tendineae and papillary muscles. Similarly, in the diastole phase the pulmonary valve returns passively to its normally closed state. This occurs by means of fibrous attachments of the pulmonary valve leaflets as integrant part of the cardiac skeleton. Practically, all the structures of the pulmonary root are dynamically involved in the valvular mechanism in both systole and diastole. Moreover, all the ventricular component structures are neurally contracted during systole and return passively to their normal state during diastole. Every type of heart valve, normally open valve or normally closed valve holds a specific valvular mechanism that operates actively during systole and passively during diastole. The sinuses of Valsalva, with their morphofunctional characteristics, confer an optimal efficiency within the active and passive valvular mechanisms of the semilunar valve. The normally closed valve is a common type of valve within the circulatory system. All the valves of the blood and lymphatic vessels of the entire circulatory system except the atrioventricular valves are normally closed valves. There are only two normally open valves within the circulatory system of the body, namely, the tricuspid and mitral valves. Certainly, the valvular mechanism of the atrioventricular valve as normally open valve is anatomically and functionally more complex than the semilunar valve, this being the reason why it is morphologically so well defined compared to the subtle mechanism of the semilunar valve. The sinuses of Valsalva are essentially involved in the mechanism of autoregulation of the coronary blood flow. This occurs by means of a remarkable anatomical trick of nature, which consists in the fact that the tow coronary ostia are located within the basic functional mechanism of the aortic valve. Hence, during ventricular systole when the aortic valve actively opens, respectively, the coronary leaflets and their Valsalva sinuses actively contract, they block the coronary orifices, creating a vacuum into the coronary arteries. In the diastole phase when the right and left coronary leaflets return passively to their normally closed position, the sinuses of Valsalva unlock the coronary orifices, during which there occurs a negative pressure into the coronary arteries, serving to reduce the pressure of blood and accelerate blood flow through coronary arteries to cardiac muscle cells. The sinus of Valsalva acts like a vacuum pump during systole and diastole for regulating coronary blood flow in proportion to the heart rate.

I present below some physiological considerations on the neural and mechanical mechanisms of the heart:

1) The central nervous system indirectly controls the coronary autoregulatory mechanical mechanism, this occurs by means of neural mechanism of the heart;

2) Coronary perfusion takes place only in the diastolic phase;

3) Left ventricular end diastolic pressure (LVEDP) is a pulmonary conditioned variable. Consequently, only in normal physiological conditions the LVEDP is proportional to the RVEDP. Under improper physiological conditions or/and specific pathological conditions this ratio may be drastically changed;

4) Whereas the left ventricular blood flow is dependent on the perfusion pressure, the coronary blood flow is dependent on the perfusion rate;

5) The heart works based on frequency; it is essentially dependent on blood volume;

6) Blood volume varies directly proportional with both the amount of metabolic end products and hepatic blood flow rate, determining blood pressure variation.