First-order approximation for the pressure-flow relationship of spontaneously contracting lymphangions

Quick, Christopher M.; Venugopal, Arun M.; Dongaonkar, Ranjeet M.; Laine, Glen A.; Stewart, Randolph H.

doi:10.1152/ajpheart.00781.2007

Cited by 29 publications

(25 citation statements)

References 33 publications

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“…Reproducing the theoretical mathematical model (15) that motivated the present work would require detailing an extensive set of assumptions and is beyond the scope of the present work. The present experimental results, however, are fully consistent with the fundamental implications of this foundational model and can be approximated by adjusting the indexes of contractility and tone in a simpler algebraic approximation detailed elsewhere (16).…”

Section: Discussionsupporting

confidence: 84%

Lymphatic pump-conduit duality: contraction of postnodal lymphatic vessels inhibits passive flow

Quick¹,

Ngo²,

Venugopal³

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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Lymphangions, the segments of lymphatic vessels between valves, exhibit structural characteristics in common with both ventricles and arteries. Although once viewed as passive conduits like arteries, it has become well established that lymphangions can actively pump lymph against an axial pressure gradient from low-pressure tissues to the great veins of the neck. A recently reported mathematical model, based on fundamental principles, predicted that lymphangions can transition from pump to conduit behavior when outlet pressure falls below inlet pressure. In this case, the axial pressure gradient becomes the major source of energy for the propulsion of lymph, despite the presence of cyclical contraction. In fact, flow is augmented when cyclical contractions are abolished. We therefore used an in vitro preparation to confirm these findings and to test the hypothesis that lymphangion contraction inhibits flow when outlet pressure falls below inlet pressure. Bovine postnodal mesenteric lymphatic vessels harvested from an abattoir were subjected to an inlet pressure of 5.0 cmH(2)O and an outlet pressure that decreased from 6.5 to 3.5 cmH(2)O under control conditions, stimulated with U-46619 (a thromboxane analog) and relaxed with calcium-free solution. Under control conditions, lymphatic flow markedly increased as outlet pressure fell below inlet pressure. In this case, the slopes of the flow versus axial pressure gradient increased with calcium-free conditions (61%, n = 8, P = 0.016) and decreased with U-46619 stimulation (21%, n = 5, P = 0.033). Our findings indicate that the stimulation of lymphatic contractility does indeed inhibit lymphatic flow when vessels act like conduits.

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Section: Discussionsupporting

confidence: 84%

Lymphatic pump-conduit duality: contraction of postnodal lymphatic vessels inhibits passive flow

Quick¹,

Ngo²,

Venugopal³

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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“…The lymphatic vessels responsible for pumping are comprised of multiple contractile segments separated by unidirectional valves to prevent backflow, termed a lymphangion, and each lymphangion performs much like a cardiac ventricle to provide unidirectional pumping. The contractile part of the lymphatic vasculature can thus be likened to a system of ventricles in series (27). The thoracic duct is the largest lymphatic vessel in the human body.…”

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confidence: 99%

Human thoracic duct in vitro: diameter-tension properties, spontaneous and evoked contractile activity

Telinius

Drewsen

Pilegaard

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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The current study characterizes the mechanical properties of the human thoracic duct and demonstrates a role for adrenoceptors, thromboxane, and endothelin receptors in human lymph vessel function. With ethical permission and informed consent, portions of the thoracic duct (2-5 cm) were resected and retrieved at T7-T9 during esophageal and cardia cancer surgery. Ring segments (2 mm long) were mounted in a myograph for isometric tension (N/m) measurement. The diameter-tension relationship was established using ducts from 10 individuals. Peak active tension of 6.24 Ϯ 0.75 N/m was observed with a corresponding passive tension of 3.11 Ϯ 0.67 N/m and average internal diameter of 2.21 mm. The equivalent active and passive transmural pressures by LaPlace's law were 47.3 Ϯ 4.7 and 20.6 Ϯ 3.2 mmHg, respectively. Subsequently, pharmacology was performed on rings from 15 ducts that were normalized by stretching them until an equivalent pressure of 21 mmHg was calculable from the wall tension. At low concentrations, norepinephrine, endothelin-1, and the thromboxane-A2 analog U-46619 evoked phasic contractions (analogous to lymphatic pumping), whereas at higher contractions they induced tonic activity (maximum tension values of 4.46 Ϯ 0.63, 5.90 Ϯ 1.4, and 6.78 Ϯ 1.4 N/m, respectively). Spontaneous activity was observed in 44% of ducts while 51% of all the segments produced phasic contractions after agonist application. Acetylcholine and bradykinin relaxed norepinephrine preconstrictions by ϳ20% and ϳ40%, respectively. These results demonstrate that the human thoracic duct can develop wall tensions that permit contractility to be maintained across a wide range of transmural pressures and that isolated ducts contract in response to important vasoactive agents. lymphatic system; lymph pump; lymphangion; lymphatic smooth muscle THE EXCESS FLUID AND PROTEIN of the interstitial spaces in almost all tissues of the body are collected and removed by the lymphatic system. The lymphatic capillaries converge into larger collecting lymphatics, and, ultimately, these terminate into large transport vessels, which return lymph to the blood circulation. The lymphatic system lacks a central pump to drive the transport of lymph. Instead, it is generally accepted that the lymphatic smooth muscle cells (LSMCs) in the collecting and transporting lymphatic vessel wall are responsible for propelling lymph forward by intrinsic contractions. The lymphatic vessels responsible for pumping are comprised of multiple contractile segments separated by unidirectional valves to prevent backflow, termed a lymphangion, and each lymphangion performs much like a cardiac ventricle to provide unidirectional pumping. The contractile part of the lymphatic vasculature can thus be likened to a system of ventricles in series (27). The thoracic duct is the largest lymphatic vessel in the human body. Under normal conditions (i.e., in healthy individuals), it is a low-flow system that drains up to 1 ml/min to the venous circulation (30,44). The volume and flow of lymph a...

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“…30 Many models focus on collecting lymphatics, often considering them to be a chain of lymphangions. 4,31,32 Fewer models consider the initial lymphatics. As examples, work by Mendoza and Schmid-Schönbein focused on flow into a lymphatic vessel across a primary valve, 24 and Roose and Swartz used homogenization theory to determine the optimal network formation in terms of fluid drainage.…”

Section: Discussionmentioning

confidence: 99%

Estimation of the Pressure Drop Required for Lymph Flow through Initial Lymphatic Networks

Sloas

Stewart

Sweat

et al. 2016

Lymphatic Research and Biology

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Background: Lymphatic function is critical for maintaining interstitial fluid balance and is linked to multiple pathological conditions. While smooth muscle contractile mechanisms responsible for fluid flow through collecting lymphatic vessels are well studied, how fluid flows into and through initial lymphatic networks remains poorly understood. The objective of this study was to estimate the pressure difference needed for flow through an intact initial lymphatic network. Methods and Results: Pressure drops were computed for real and theoretical networks with varying branch orders using a segmental Poiseuille flow model. Vessel geometries per branch order were based on measurements from adult Wistar rat mesenteric initial lymphatic networks. For computational predications based on real network geometries and combinations of low or high output velocities (2 mm/s, 4 mm/s) and viscosities (1 cp, 1.5 cp), pressure drops were estimated to range 0.31-2.57 mmHg. The anatomical data for the real networks were also used to create a set of theoretical networks in order to identify possible minimum and maximum pressure drops. The pressure difference range for the theoretical networks was 0.16-3.16 mmHg. Conclusions:The results support the possibility for suction pressures generated from cyclic smooth muscle contractions of upstream collecting lymphatics being sufficient for fluid flow through an initial lymphatic network.

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First-order approximation for the pressure-flow relationship of spontaneously contracting lymphangions

Cited by 29 publications

References 33 publications

Lymphatic pump-conduit duality: contraction of postnodal lymphatic vessels inhibits passive flow

Lymphatic pump-conduit duality: contraction of postnodal lymphatic vessels inhibits passive flow

Human thoracic duct in vitro: diameter-tension properties, spontaneous and evoked contractile activity

Estimation of the Pressure Drop Required for Lymph Flow through Initial Lymphatic Networks

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