Lymphatic capillaries

Lymphatic capillaries (vasa lymphocapilldria) are the initial link - the "roots" of the lymphatic system. They are present in all organs and tissues of the human body, except for the brain and spinal cord, their membranes, the eyeball, the inner ear, the epithelial covering of the skin and mucous membranes, cartilage, the parenchyma of the spleen, bone marrow and placenta. Unlike blood capillaries, lymphocapillaries have a larger diameter (from 0.01 to 0.2 mm), uneven contours, lateral protrusions. When connected to each other, they form closed lymphocapillary networks (rete lymphocapillar) in organs and tissues. The loops of these networks lie in one or several planes depending on the structure (construction) of the organ in which they are located. The orientation of the capillaries corresponds to the direction of the connective tissue bundles in which the lymphatic capillaries are located. Thus, in volumetric organs (muscles, lungs, liver, kidneys, large glands, etc.), the lymphocapillary networks have a three-dimensional structure. The lymphatic capillaries in them are oriented in different directions, located between the structural and functional elements of the organ: bundles of muscle fibers, groups of glandular cells, renal corpuscles and tubules, liver lobules. In flat organs (fascia, serous membranes, skin, layers of the walls of hollow organs, walls of large blood vessels), the lymphocapillary networks are located in one plane parallel to the surface of the organ. In some organs, the network of lymphatic capillaries forms finger-shaped long blind protrusions (for example, lymphatic sinuses in the villi of the small intestine).

The walls of lymphatic capillaries are built from a single layer of endothelial cells. These cells are attached to adjacent bundles of collagen fibers by means of bundles of the finest fibers - sling (anchor) filaments. Such a connection of collagen fibers and the walls of lymphatic capillaries facilitates the opening of the lumen of the latter, especially in the case of edema of the tissues in which these capillaries are located. Lymphatic capillaries that have valves are considered lymphatic postcapillaries.

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