Valvular heart apparatus
Author Ольга Кияница
Heart valves are needed for portioning the blood out during the contraction of the heart.Their main function is to prevent reverse outflow of blood (regurgitation) and to ensure that it is by heart always moving in one direction. Closure of the heart valves can be heard, usually with a stethoscope, which can be used to initially diagnose the pathological conditions associated with the valve apparatus.
Video: Human heart structure, circulatory circles
All valves of the heart are covered with endothelium. The three layers that form the basis of the valve apparatus have specific characteristics and are called fibrosis, spongiosa and ventricularis (fibrosa, spongiosa and ventricularis). During heartbeats, spongiosa, rich in glycosaminoglycans, facilitates the process of regrouping collagen and elastic fibers.
Vascular interstitial cells (VIC) are found in abundance in all layers of the heart valves and contain a variety of dynamically directed components. Regulation of collagen and other structural components is provided by enzymes synthesized by VIC. Valve tissue integrity is maintained by the interaction of valvular endothelial cells (KEC) with VIC.Changes and remodeling of the valvular interstitial and endothelial structures contribute to the disruption of the valve's properties, and later of the valve function.
Fundamentals of the correct operation of the valve apparatus:
- The valves are correctly formed and flexible.
- Valves are fully opened, which allows the necessary amount of blood to pass through the hole
- Valves are tightly closed, then the blood does not flow back
The tricuspid valve located at the mouth of the aorta separates the left ventricular cavity from the aorta. For the three semilunular valves (right coronary, left coronary and posterior non-coronary) of the aortic valve, there are enlarged pockets of the aortic aperture, called the sinuses of Valsalva. The right coronary sinus departs from the right coronary artery, from the left coronary sinus - the left coronary artery. The area where all three valves converge is called commissure.
The opening and closing of the aortic valve is a passive mechanism controlled by pressure, in contrast to the mitral valve.
The tissue of the aortic valves is stretched as a result of counteraction during diastole, elastin is elongated and stretched. Therefore, normally the valves of the aortic valve are quite flexible and durable, able to withstand systemic pressure. In the systole phase, the recoil of elastin provides relaxation and shortening of the valve. The optimum function of the valve requires an ideal alignment of the three return points.
Associated diseases: aortic regurgitation (also called aortic insufficiency), aortic stenosis.
The mitral valve
The mitral valve was named after the miter by Andreas Veslius (De Humani Corporis Fabrica, 1543). This valve is located at the junction of the left atrium and left ventricle. Its device consists of five functional components:
- an annular space;
- tendon chords;
- papillary muscles;
- near located myocardium.
Fibrous ring is a zone of connective tissue, which contains intermittent fibrous and muscle fibers that connect with the left atrium and the ventricle. The front flap covers about one-third of the primary fibrous front of the ring. A portion of the anterior mitral valve flap is in close proximity to the annular opening of the aortic valve. The ventricular, posterior, valve is attached to the posterior muscular half and two-thirds of the annular space. Because of asymmetric leaflets, the aperture of the mitral valve has the shape of a funnel.
Each chord is attached chords both from the anterior and posterior papillary muscles. Papillary muscles contract and pull chords during systole, which in turn contribute to the closure of the valves of the mitral valve.
Separately, a mitral-valve complex including mitral valve and left atrioventricular myocardium, endocardium and part of the aorta are isolated. This formation contributes to the outflow of blood from the left ventricle. Forced blood flow through the valve, as well as its tight closure during systole, is ensured by the concerted action of the mitral-valve complex.
Related diseases: mitral valve prolapse, mitral valve regurgitation, mitral valve stenosis.
Pulmonary artery valve
It is also known as a pulmonary valve. The structure of the pulmonary valve is similar to that of the aortic valve. The valves have a semilunar form, in the norm there are three (anterior, left and right). Like the valves are called sinuses, which by means of an arched ring (sinotobular junction) are combined with a pulmonary trunk. Like the other valves, the pulmonary also has a fibrous ring and commissure.
Related diseases: stenosis of the pulmonary valve, regurgitation of the pulmonary valve.
It is also known as the tricuspid valve. Located in the right side of the heart at the junction of the atrium and ventricle. It consists of 3 valves, chordal tendons (anterior, posterior) and often defined third papillary muscle. The tricuspid valve does not have a well-defined collagen ring. Three leaflets are attached to a fibrous ring of elliptical shape. Direct attachment of the leaflet is a distinctive feature of the tricuspid valve. Outstanding papillary muscles support the valves in commissures.
Normal valve function requires structural integrity and coordinated interactions between several anatomical components.Various pathophysiological mechanisms can cause heart valve disease.
Associated diseases: tricuspid valve atresia, tricuspid regurgitation, tricuspid stenosis.
In the normal state, the valves function with strict ordering, which enables the heart chambers to contract properly and to eject blood in the right amount. There are four main stages of the valvular apparatus:
1. Atrioventricular valves are opened (mitral and tricuspid), as a result of which the blood rushes from the upper parts of the heart to the lower ones.
2. When filling the ventricles in their cavity, the pressure rises, whereupon the valves are closed. When the ventricles contract, the blood fills the atrium again (venous - right and arterial - left).
3. Aortic and pulmonary valves are opened. This also happens under pressure when the ventricles contract and the blood is pushed into large vessels and either to the lungs (from the right ventricle) or to all organs and tissues (from the left ventricle).
4. During relaxation of the ventricles of the pulmonary and aortic valves close. At this time, atrioventricular valves are opened and the blood flows back to the ventricles from the atria for the next release into the bloodstream.
In the formation of heart tones, the valvular apparatus takes direct part, changing various types of noise.
If, for example, the valve is not completely closed, then the blood returns to the previous chamber, creating a characteristic noise (eg, systolic murmur in mitral failure).
When the valves are stenosed, the blood flow passes through the hole with great difficulty, which causes noise with other features (for example, diastolic noise with tricuspid valve stenosis).
- The first tone of the heart
Occurs due to closure of the valves atrioventricular location (mitral and tricuspid). It begins with the beginning of the ventricular systole and is best heard in the hearing of the apex of the heart
When determining additional sound components, it is assumed that there is a fluctuation in the blood in the ventricular chambers, a vibration of the chamber walls or a turbulent blood flow discharged through the aortic aperture into the Valsalva sinus.
- Second heart tone
Its appearance is associated with the closure of the aortic and pulmonary valves, as well as with fluctuations of blood in the aorta
Since the closure of the right and left half-moon valves does not occur simultaneously, the second heart sound is most often divided into two.
- Third heart tone
Formed in the phase of early diastole and associated with rapid filling of the blood of the ventricles immediately after isometric relaxation. Sometimes this sound is heard in small children, but usually it is not perceived by the ear.
- The fourth heart tone
It occurs against the background of atrial contraction at the beginning of the cardiac cycle. In most cases, the stethoscope is not tapped.
Thus, when auscultation can be clearly heard only the first and second tone, which, depending on the place of auscultation, are listened to in different ways. If a phonocardiogram is done, then the severity of the tone and its correspondence to the systole or diastole can be clearly traced.
Electrocardiography is the main method for studying the electrical activity of the heart. Many heart diseases are determined precisely by an ECG, which is additionally a relatively affordable way to diagnose. To obtain accurate results, electrodes must be properly applied during ECG recording.
In diagnostics of cardiovascular diseases an important role is played by timely diagnostics. It is often enough to conduct a standard ECG to make a correct diagnosis. In other cases, a diverse study of the heart is required, which allows you to establish the exact cause of the illness and conduct an effective treatment.
Tens of thousands of implantations of pacemakers are performed annually. In some cases, they are installed only for a while, with other indications the device is used on a permanent basis. In both variants, the main goal of using a heart stimulant is to improve the quality of a person's life.