Lymphatic vessels

Lymphatic vessels (vasa lymphatica)-containers, conducting lymph from tissues in venous bed. Lymphatic vessels are located almost in all organs and tissues. The exception is the epithelial layer of the skin and mucous membranes, cartilage, sclera, vitreous body and the lens of the eye, the brain, the placenta and the parenchyma of the spleen.
The beginning of the formation of the lymphatic system, the embryo of the person belongs to the 6th week of development, when it is already possible to distinguish between paired jugular lymph bags. By the beginning of the 7th week, these bags are connected with the front cardinal veins. Later, the rest of the lymph bags. The growth of lymphatic vessels of the primary bags provided by the proliferation of endothelial processes. Valves HP laid on 2-5 months uterine life in the form of a flat annular bulges of the endothelium.
Among HP are distinguished: lymphatic capillaries; small intraorganic HP; extraorgan (the so-called discharge) HP; HP connecting lymph nodes; large trunks - lumbar (trunci lumbales dext. et sin.), intestinal (tr. intestinalis), subclavian (trr. subclavii dext. et sin.), bronchomediastinal (trr. bron-chomediastinales dext. et sin.), jugular (trr. jugulares dext. et sin.), emerging from the lymph vessels of appropriate areas, and two lymphatic duct - breast - (ductus thoracicus) and right (ductus lymphaticus dext.). Both of these duct fall respectively to the left and right in the confluence of the internal jugular and subclavian veins.
The combination of lymphatic capillaries is like the source of the lymphatic system. In the lymphatic capillaries come from tissue products of metabolism. The wall of the capillary is composed of endothelial cells with weakly expressed the basement membrane. Diameter of lymphatic capillary exceeds the diameter of the blood vessels. In the body produce superficial and deep network of lymphatic capillaries, which are interconnected. The transition lymphatic capillaries in the following HP is determined by the presence of valves. Along with considerable fluctuations caliber for HP characterized by a narrowing in the locations of the valves. Small intraorganic HP caliber 30-40 micron not have the muscle membrane. The lymphatic vessels by 0.2 mm calibre and above the wall consists of three layers: the inner (tunica's intima), medium muscle (tunica media) and external connective tissue (tunica adventitia). Valves HP are the folds of the inner lining. Valves in HP and the distance between them vary. The distance between the valves in small HP is equal to 2-3 mm, in the larger 12 - 15 mm, the Valves provide the lymph flow in one direction. In pathologically advanced HP appears failure of the valves must be retrograde flow of lymph.
Number of lymph capillaries penetrating in a separate small gathering lymphatic vessels, ranging from 2 to 9. Intraorganic HP form in the bodies Shirokopolosnye plexus with different shape of loops. They often accompany the blood vessels, forming by transverse and oblique anastomoses. From the organ or body part out several groups outlet L. E., which merge to go to the regional lymph nodes. Discharge HP small intestine, passing in the mesentery, called the milky (vasa chylifera), as they are a milky juice (chylus).
The lymph flow in HP is determined by the contractile ability of their walls, mechanical influence of active and passive movements and energy limpopoprovince. The pressure in the discharge HP varies with different functional state of the body.
HP good regenerate. Through 3-20 weeks severed vessels are completely restored. L. c., as blood, have their own supply their wall vessels (vasa vasorum). Innervation HP is nervous plexuses, available in the wall of the vessel; in adventitia and the middle layer of the wall was found free nerve endings.
Pathology of lymphatic vessels - see the Thoracic duct, Lymphangioma, Lymphangitis, Lymphangiectasia, Cholangiomas.