Semilunar valves - their definition is given in this article. In addition, after reading the information below, you can learn about the operation of such valves in the human body, about their structure, about the places where they are located. Information, no doubt, will be of interest to everyone who is interested in human anatomy.
Valve definition
In the body, which is a complex mechanism, there are many adaptations in order to direct the flows in the right direction. Such devices are located in the heart muscle - they are more complex. They are also located in capacitive vessels of various sizes.
The valve apparatus is a set of anatomical structures that, when working together, prevent the reverse (retrograde) movement of blood.
Varieties of heart valves
- The first group is the structures separating the ventricles and atria.
- Second group - valves located at the junction with the aorta and the trunk of the pulmonary artery, in the area where these vessels depart from the ventricles of the heart.
Aortic and pulmonary valves have the following structures:
1. Semilunar flaps (semilunarheart valves).
2. Spaces between dampers (flap triangles).
3. Sinuses.
4. Fibrous rings (the existence of which is debated).
Semilunar flaps
Since the semilunar shape in these valves is only the valves entering them, it is correct to call these valves the aortic valve and the semilunar valve of the pulmonary trunk. Both valves have three flaps. The aortic valve has right, left, and posterior flaps. And the valve of the pulmonary trunk has an anterior instead of a posterior one.
The size of the flaps differs in people of different ages, there are also individual characteristics. As a rule, the semilunar valves of the aorta are wider in width than the aortic sinuses, and, on the contrary, they are smaller in height. This structure contributes to their displacement downward and valve closure when they are filled with blood. The orifices of the coronary arteries are located in the sinuses of the aorta.
The semilunar valves are located near the annulus fibrosus. They are formed by the fold of the endocardium. There are front, left and right crescent flaps. Their lower edges are connected to the ends of the sinuses. The flaps and sinuses form holes. The crescent flaps are slightly larger than the sinuses of the pulmonary trunk.
Aortic and pulmonary valve sinuses
The sinuses of the aorta and pulmonary artery are the spaces between each of the semilunar valves and the wall of the vessel.
The height of the adult aortic sinuses is 1.7-2 cm, their depth is from 1.5 to 3 mm. deepeningsinuses occur with age. The spaces between adjacent flaps are triangular in shape, with the base facing the ventricles. Triangles are made up of collagen and elastic fibers, they connect the flaps together and form the fibrous rings of the valves.
An oval fibrous structure with three teeth, resembling a crown, forms at the base of the aorta.
As part of the pulmonary trunk, three sinuses are usually distinguished: anterior, left and right. Sometimes there are two sinuses. The sizes of these sinuses differ significantly in different age groups, and also have individual characteristics. In adults, the left sinus is 19-32 mm wide, 12-16 mm high, the right 20-32 mm and 10-15 mm high. Front 20-30mm and 10-15mm respectively.
Not everyone recognizes the existence of a fibrous structure at the base of the pulmonary trunk.
Valve mechanism
The crescent semilunar valve prevents blood from returning to the ventricles.
During the contraction of the heart muscle, the blood in the ventricles moves in two directions: towards the semilunar valves, and towards the atria. Having reached the atrioventricular valves, the blood hits them and the valves close. The pressure in the cavity of both ventricles increases. The pressure on the crescent semilunar valve increases and exceeds that in the aorta and pulmonary artery. The only way out of the blood is the movement of the flow into the aorta, and from the right ventricle - into the pulmonary trunk. In this situation, the cuspid valves are closed and the semilunar valves are open.
Whencurrent from the cavity of the left ventricle rushes towards the aorta, then this current presses the semilunar valves against the wall of the aorta. After the expulsion of blood from the cavity of the ventricle, the sinuses of the aorta slam shut. Relaxation of the ventricles occurs, and the blood ejected into the artery tends back to the heart, into the left ventricle. The sinuses of the artery fill with blood, and the crescent valves of the aorta close. Blood does not flow back into the ventricle.
This is how the pulmonary semilunar valve works.
Aortic and pulmonary valves prevent the backflow of blood from large vessels into the ventricular cavity at the end of systole.
Semilunar valves of vessels
In the body there is a variety of semilunar valves, which have a simpler structure than the heart, but their function remains the same. These are structures that prevent retrograde blood flow.
Semilunar valves are located in some veins (legs, upper extremities), as well as in the lymphatic vessels.
The venous system is represented by a network of resistive vessels, the function of which is to transport blood to the right parts of the heart against gravity. The vessels of the venous system have a less developed muscular membrane than in the arteries. They have different mechanisms for supplying blood from the lower sections to the heart. One of the adaptive mechanisms is the presence of semilunar valves.
Venous valves have two leaflets, valve ridges and parts of the vessel wall. Valve structures are located in greater numbers in the veins of the legs. For example: the great saphenous vein has up to ten venous valves.
Pathologies
If the integrity or function of the valves is impaired as a result of injury or inflammation, pathological conditions develop that must be recognized and proper therapy initiated (acute or long-term heart failure with damage to the heart valves).
A well-known pathology of the veins associated with disruption of the valves is varicose disease of the legs, which is dangerous for its complications (thrombophlebitis, swelling of the legs, blockage of the pulmonary artery). Currently, modern medicine has a number of effective ways to restore the normal functioning of the body, in particular, the valves in question. Naturally, in each case, an individual approach to a sick person is determined.
Thus, we examined the functions of the semilunar valves, their role in the overall functioning of the human body, the problems that can be caused by violations and pathologies associated with the valves.
