Lymphatic vessels
Last reviewed: 23.04.2024
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Lymphatic vessels (vasa lymphatica) are formed by the fusion of lymphatic capillaries. The walls of the lymph vessels are thicker than the walls of the lymphocapillaries. In intragmental and often extraorganic lymphatic vessels, outwardly from the endothelium, there is only a thin connective tissue membrane (non-muscle vessels). The walls of the larger lymphatic vessels consist of three shells: the inner endothelium (tunica interna), the medial muscular (tunica media) and the outer connective tissue (tunica externa, s.adventitia).
Lymphatic vessels have valves (valvulae lymphaticae). The presence of valves gives these vessels a characteristic clear-cut appearance). Valves of lymphatic vessels, adapted to pass lymph only in one direction - from the "periphery" towards the lymph nodes, trunks and ducts, are formed by folds of the inner shell with a small amount of connective tissue in the thickness of each leaf. Each valve consists of two folds of the inner shell (flaps) located opposite each other. The distance between adjacent valves is from 2-3 mm for intraorganic lymph vessels to 12-15 mm in larger (extraorganic) vessels. The adjacent intraorganic lymph vessels anastomose with each other, forming networks (plexuses), whose loops have various shapes and sizes.
From the internal organs, the muscles, the lymphatic vessels usually go out next to the blood vessels - these are the so-called deep lymphatic vessels (vasa lymphatica profunda). Superficial lymphatic vessels (vasa lymphatica superficialia), located outside of the superficial fascia of the human body, are located next to or near the subcutaneous veins. These vessels are formed from the lymphatic capillaries of the skin, subcutaneous tissue. In mobile places, in the places of body bends (near the joints), lymphatic vessels divide, forming roundabout (collateral) paths, which provide a continuous current of lymph in the course of changes in the position of the body or its parts, as well as in violation of the patency of some lymphatic vessels during flexion- in joint movements.
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