Lymphatic pumping: mechanics, mechanisms and malfunction

• Published in: The Journal of physiology Vol. 594; no. 20; pp. 5749 - 5768
• Main Authors: Scallan, Joshua P., Zawieja, Scott D., Castorena‐Gonzalez, Jorge A., Davis, Michael J.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 15.10.2016; John Wiley and Sons Inc
• Subjects: Animals; Cardiovascular Physiology; Humans; Lymph - physiology; lymphatic; Lymphatic system; Lymphatic System - physiology; Lymphatic Vessels - physiology; lymphedema; muscle contraction; Muscle Contraction - physiology; Muscle, Smooth - physiology; Pressure; Topical Review; Topical Reviews; Vasculature; muscle contraction; lymphedema; lymphatic
• ISSN: 0022-3751; 1469-7793; 1469-7793
• DOI: 10.1113/JP272088

A combination of extrinsic (passive) and intrinsic (active) forces move lymph against a hydrostatic pressure gradient in most regions of the body. The effectiveness of the lymph pump system impacts not only interstitial fluid balance but other aspects of overall homeostasis. This review focuses on the mechanisms that regulate the intrinsic, active contractions of collecting lymphatic vessels in relation to their ability to actively transport lymph. Lymph propulsion requires not only robust contractions of lymphatic muscle cells, but contraction waves that are synchronized over the length of a lymphangion as well as properly functioning intraluminal valves. Normal lymphatic pump function is determined by the intrinsic properties of lymphatic muscle and the regulation of pumping by lymphatic preload, afterload, spontaneous contraction rate, contractility and neural influences. Lymphatic contractile dysfunction, barrier dysfunction and valve defects are common themes among pathologies that directly involve the lymphatic system, such as inherited and acquired forms of lymphoedema, and pathologies that indirectly involve the lymphatic system, such as inflammation, obesity and metabolic syndrome, and inflammatory bowel disease. Diagram depicting the major factors regulating the effective pumping ability of a prenodal collecting lymphatic vessel as it transports lymph formed in lymphatic capillaries to the subcapsular sinus of a lymph node. Pressures indicate approximate hydrostatic pressures measured in the interstitium and at the entrance to the lymph node, respectively, that have been recorded in many regions of the lymphatic system. Cut‐away sections show the locations of two valves. The blue shaded region depicts the relatively modest net filtration of fluid and solute that occurs under normal conditions all along the length of the collecting vessel. Each of these factors can also become a target of lymphatic dysfunction. AP, action potential; LEC, lymphatic endothelial cell; LMC, lymphatic muscle cell.