Lymph capillaries or lymphatic capillaries are tiny, thin-walled

microvessel The microcirculation is the circulatory system, circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within organ (anatomy), organ Tissue (biology), tissues. The microvessels include terminal ar ...

s located in the spaces between cells (except in the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

and non-vascular tissues) which serve to drain and process

extracellular fluid In cell biology, extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 50–60% (range 45 to 75%) of total body weight; women and the obese typically ha ...

. Upon entering the lumen of a lymphatic capillary, the collected fluid is known as lymph. Each lymphatic capillary carries lymph into a

lymphatic vessel The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...

, which in turn connects to a lymph node, a small bean-shaped gland that filters and monitors the lymphatic fluid for infections. Lymph is ultimately returned to the venous circulation. Lymphatic capillaries are slightly larger in diameter than blood capillaries, and have closed ends (unlike the loop structure of blood capillaries). Lymph capillaries are strategically placed among the blood-related capillaries in order to have efficient and effective uptake from the interstitial fluid during capillary exchange. This intentional formation allows for a more rapid and continuous collection. Their unique structure permits interstitial fluid to flow into them but not out. The ends of the endothelial cells that make up the wall of a lymphatic capillary overlap. When pressure is greater in the interstitial fluid than in lymph, the cells separate slightly, like the opening of a one-way swinging door, and interstitial fluid enters the lymphatic capillary. When pressure is greater inside the lymphatic capillary, the cells adhere more closely, and lymph cannot escape back into the interstitial fluid. Attached to the lymphatic capillaries are anchoring filaments, which contain elastic fibers. They extend out from the lymphatic capillary, attaching lymphatic endothelial cells to surrounding tissues. When excess interstitial fluid accumulates and causes tissue swelling, the anchoring filaments are pulled, making the openings between cells even larger so that more fluid can flow into the lymphatic capillary.Tortora, Gerard J.: "Principles of Human Anatomy - 10th edition", page 512. John Wiley and Sons, Inc., 2005. lymph enters the lymph capillaries by osmosis Lymph capillaries have a greater internal oncotic pressure than blood capillaries, due to the greater concentration of plasma proteins present.

Clinical importance

In the small intestine, lymphatic capillaries called

lacteal A lacteal is a Lymph capillary, lymphatic capillary that absorbs dietary fats in the Intestinal villus, villi of the small intestine. Triglycerides are emulsified by bile and hydrolyzed by the enzyme lipase, resulting in a mixture of fatty acids, ...

s are critical for the transport of dietary lipids and lipid-soluble vitamins to the bloodstream. In the small intestine, dietary

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

s combine with other lipids and proteins, and enter the lacteals to form a milky fluid called

chyle Chyle (; ) is a milky bodily fluid consisting of lymph and emulsified fats, or free fatty acids (FFAs). It is formed in the small intestine during digestion of fatty foods, and taken up by lymph vessels specifically known as lacteals. The lip ...

. The chyle then travels through the lymphatic system, eventually entering the bloodstream.

References

{{DEFAULTSORT:Lymph Capillary Lymphatic organ anatomy Angiology