Pulmonary valve

The valve of the pulmonary artery is separated from the fibrous carcass of the heart by the muscular septum of the outlet section of the right ventricle. It does not have a fibrous support. Its semilunar base rests on the myocardium of the outlet part of the right ventricle.

The valve of the pulmonary artery, similar to the valve of the aorta, consists of three sinuses and three semilunar wings that extend from their bases from the fibrous ring. Semilunar wings originate from the medial margin. There are front, left and right semilunar valves, the proximal edges of which continue in the lateral direction in the form of sinuses, and their free edges protrude into the pulmonary trunk. The thickened fibrous part of the central zone of coagulation of each leaf is called Morganyi's nodules. Accordingly, the valves are called the sinuses of the valve of the pulmonary artery. Expansion of the primary pulmonary artery is not as well expressed as in the aorta

The commissures between the valves are designated as left, right and posterior. The left half-lumbar leaf directly borders on the muscular tissue of the outlet of the right ventricle, its septum and partly with the upper part of the supraventricular crest. The right flap is also located in the myocardium of the outlet section of the right ventricle. The rear commissure is located opposite the "intercoronary" commissure of the aortic valve. Elements that form the valve of the pulmonary artery vary significantly in their structure. Sinotubular connection (arched ring, arched comb), commissural rods of the valve base are connected to each other in a spatially interconnected elastic framework, to which flaps and sines are attached.

The sine wall in the region of the arch ring has a structure similar to the wall of the pulmonary trunk, with a well-defined middle layer consisting of smooth myocytes and surrounded by elastin and collagen fibers. Toward the fibrous ring of the valve base, the sinus wall becomes thinner, the number of elastin fibers and myocytes decreases, the collagenous increases and at the base becomes a fibrous strand. At the same time, the inner elastic membrane is gradually lost.

The fibrous ring of the base, which has a pulmonary artery valve, begins with a bifurcation of the fibrous sine sinus. One part of it forms a sinus wall of the fibrous ring, which then passes to the sash and forms its sinus layer. The other part forms the base of the triangle of the fibrous ring and braids the cardiomyocytes. The fibrous ring is triangular in cross-section and consists mainly of collagen structures, an elastic membrane along its ventricular surface and, to a lesser extent (about 10%), a chondroid tissue. The tissues that make up the middle part of the fibrous ring go into the sash and form its middle layer. The valve has a three-layer structure and consists of the ventricular, median and sinus layer. The thickness of the leaf is maximal in the fibrous ring and is minimal in the dome. In the area of the nodule of the semilunar flap, the thickness of the flap increases again. Here, a loose median layer bordered by the elastic membrane of the ventricular layer predominates. At the base of the valve, there is a significant number of arterioles, veins and capillaries providing its blood supply. The commissural rods consist of three sections: an arched region having the structure of the arched ridges and being a continuation of them, a fibrous region consisting mainly of unscrewed collagen bundles braided with sharply crimped collagen fibers having a structure similar to the fibrous base ring and a transition site from the first to the second.

The valve of the pulmonary artery can be considered as a composite structure consisting of a strong, mainly collagenic framework and shell elements (valves and sinuses) that have anisotropic properties. The valve of the pulmonary artery has the same biomechanics as the aortic valve.

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