Title: Lymphatic capillaries
(A): Lymphatic capillaries (loose connective tissue in region subcutis of the skin, Azan staining, human. (1) The lumen of the lymphatic capillary is a little dilated. Surrounding loose connective tissue (2) is slightly edematous.
(B): Lymphatic capillaries (lymph node region), toluidine blue 1 µm plastic section, guinea pig. Lumen tubular lymphatic capillary with extremely flat lining endothelium (1), small-sized muscular artery (2). Ultrastructurally lymphatic capillaries are lined with a continuous endothelium without tight junction. Fenestrated endothelia as well as endothelia with gaps are also found. The discontinuous basal lamina, however, facilitates passage of large molecules and cells.
Background: In contrary to the cardiovascular system the lymphatic system is not a closed system. Lymphatic capillaries are almost present everywhere except in epithelia, cartilage and bone tissue, bone marrow and placenta. Blind-ending lymphatic capillaries are responsible for the absorption of the interstitial tissue fluid. When interstitial tissue fluid enters the initial lymphatic capillaries the fluid is called lymph and contains i.a. surplus of interstitial tissue fluid, waste products, circulating white blood cells. The lymph will be transported via lymph nodes to the lymphatic ducts that drain into the subclavian vein and subsequently toward the heart. The propeller action is provided by peristalsis (smooth muscle contractions in the wall of the lymphatic vessels) as well as the contractions of surrounding skeletal muscles.
Keywords/Mesh: vascularization, lymphatic system, lymphatic,, capillary, small muscular artery, discontinuous basal lamina, endothelium, lymph, interstitial fluid, histology, POJA collection