Secomb T W, Hsu R, Pries A R
Department of Physiology, University of Arizona, Tucson 85724-5051, USA.
Am J Physiol. 1998 Mar;274(3):H1016-22. doi: 10.1152/ajpheart.1998.274.3.H1016.
The interior surfaces of capillaries are lined with a layer (glycocalyx) of macromolecules bound or absorbed to the endothelium. Here, a theoretical model is used to analyze the effects of the glycocalyx on hematocrit and resistance to blood flow in capillaries. The glycocalyx is represented as a porous layer that resists penetration by red blood cells. Axisymmetric red blood cell shapes are assumed, and effects of cell membrane shear elasticity are included. Lubrication theory is used to compute the flow of plasma around the cell and within the glycocalyx. The effects of the glycocalyx on tube hematocrit (Fahraeus effect) and on flow resistance are predicted as functions of the width and hydraulic resistivity of the layer. A layer of width 1 micron and resistivity 10(8) dyn.s/cm4 leads to a relative apparent viscosity of approximately 10 in a 6-micron capillary at discharge hematocrit 45% and flow velocity of approximately 1 mm/s. This is consistent with experimental observations of increased flow resistance in microvessels in vivo, relative to glass tubes with the same diameters.
毛细血管的内表面衬有一层与内皮细胞结合或吸附的大分子（糖萼）。在此，使用理论模型来分析糖萼对毛细血管中血细胞比容和血流阻力的影响。糖萼被表示为抵抗红细胞穿透的多孔层。假定红细胞形状为轴对称，并考虑细胞膜剪切弹性的影响。利用润滑理论计算细胞周围和糖萼内的血浆流动。预测糖萼对管血细胞比容（法厄效应）和流动阻力的影响是该层宽度和水力电阻率的函数。在排出血细胞比容为45%且流速约为1毫米/秒的6微米毛细血管中，宽度为1微米且电阻率为10⁸达因·秒/厘米⁴的一层会导致相对表观粘度约为10。这与体内微血管相对于相同直径玻璃管血流阻力增加的实验观察结果一致。
