Abstract
Using information from the deep dissection, microobservation, and measurement of acupoints in the upper and lower limbs of the human body, we developed a three-dimensional porous medium model to simulate the flow field using FLUENT software and to study the shear stress on the surface of interstitial cells (mast cells) caused by interstitial fluid flow. The numerical simulation results show the following: (i) the parallel nature of capillaries will lead to directional interstitial fluid flow, which may explain the long interstitial tissue channels or meridians observed in some experiments; (ii) when the distribution of capillaries is staggered, increases in the velocity alternate, and the velocity tends to be uniform, which is beneficial for substance exchange; (iii) interstitial fluid flow induces a shear stress, with magnitude of several Pa, on interstitial cell membranes, which will activate cells and lead to a biological response; (iv) capillary and interstitial parameters, such as capillary density, blood pressure, capillary permeability, interstitial pressure, and interstitial porosity, affect the shear stress on cell surfaces. The numerical simulation results suggest that in vivo interstitial fluid flow constitutes the mechanical environment of cells and plays a key role in guiding cell activities, which may explain the meridian phenomena and the acupuncture effects observed in experiments.
Highlights
Interstitial fluid flow is the movement of fluid through the extracellular matrix of tissues, often between blood and lymphatic vessels
Apart from its role in mass transport, interstitial fluid flow provides a specific mechanical environment that is important for the physiological activities of interstitial cells [2, 3]
In vitro numerical simulations of how the architecture of extracellular fibers affects the shear stress on cell membranes showed that interstitial fluid flow is important to the fluid force on a cell imbedded in a 3D matrix [9, 10]
Summary
Interstitial fluid flow is the movement of fluid through the extracellular matrix of tissues, often between blood and lymphatic vessels. This flow provides a necessary mechanism for transporting large proteins through the interstitium and constitutes an important component of microcirculation [1]. Li et al visualized regional hypodermic migration channels in the interstitial fluid of humans using magnetic resonance imaging (MRI) [15] These channels were different from those of lymphatic or blood vessels and partially coincided with the characteristics of meridians. Evidence-Based Complementary and Alternative Medicine solution with heparin was infused simultaneously through an axillary artery and a vein [16] This phenomenon demonstrates that the movement of an isotope along meridians requires an impetus, which is provided by circulating blood in living beings.
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