Canham P B, Potter R F, Woo D
J Physiol. 1984 Feb;347:697-712. doi: 10.1113/jphysiol.1984.sp015091.
The finer and more closely arrayed the capillaries are, the more efficiently oxygen will be transported to tissue because the same blood volume has greater contact area with the tissue and the diffusion distance for the oxygen is minimized. If these principles are actually governing microvascular structure, then the finest capillaries will be the narrowest channels which circulating erythrocytes can transit. Ascertaining the existence of this geometric limit requires quantitative data of demonstrated reliability on erythrocyte geometry and on capillary diameters. The study was done on Wistar rats. Constant flow perfusion of skeletal and cardiac muscle by a modified Batson's compound for anatomical casting made available rigid three-dimensional replicas of the microvasculature which shrank less than 1% when the tissue was digested with potassium hydroxide. Measurements of individual capillaries were made on high contrast scanning electron micrographs of the casts. Measurements on individual rat erythrocytes were done on photomicrographs of cells on edge. Reliability of these data was tested in three ways. First, repeatability of the tracing of the cell outline was tested by processing a duplicate set of photomicrographs. Secondly, correlations of the various parameters were found. Thirdly, results from other techniques of measuring erythrocytes were examined for areas of agreement and also for causes of possible error for areas in dispute. Because of known variability in erythrocyte sizes and shapes between species and between individuals within a species, we compared the data on erythrocyte geometry and capillary diameters for samples taken from the same individual rat. The data revealed a very positive indication that the lowest range of capillary diameters were at the limits of deformation of the circulating erythrocytes. Ninety-five per cent of the erythrocytes sampled could pass through a channel 2.9 micron in diameter. A small number of the capillaries measured were narrower than this limit. The data on erythrocytes and capillaries were compared for six rats. The limiting diameter for passage of erythrocytes was remarkably uniform for all six animals.
毛细血管越细且排列越紧密，氧气输送到组织的效率就越高，因为相同体积的血液与组织的接触面积更大，氧气的扩散距离也最小化。如果这些原理确实决定了微血管结构，那么最细的毛细血管将是循环红细胞能够通过的最窄通道。确定这种几何极限的存在需要关于红细胞几何形状和毛细血管直径的具有可靠证明的定量数据。该研究是在Wistar大鼠身上进行的。通过改良的巴特森化合物对骨骼肌和心肌进行恒流灌注以制作解剖铸型，从而获得微血管的刚性三维复制品，当用氢氧化钾消化组织时，该复制品收缩小于1%。在铸型的高对比度扫描电子显微镜照片上对单个毛细血管进行测量。在边缘细胞的显微照片上对单个大鼠红细胞进行测量。这些数据的可靠性通过三种方式进行测试。首先，通过处理一组重复的显微照片来测试细胞轮廓追踪的可重复性。其次，找出各种参数之间的相关性。第三，检查其他测量红细胞技术的结果，以找出一致的领域以及争议领域可能存在误差的原因。由于已知不同物种之间以及同一物种内个体之间红细胞大小和形状存在差异，我们比较了从同一只大鼠身上采集的样本中红细胞几何形状和毛细血管直径的数据。数据显示出非常积极的迹象，即毛细血管直径的最低范围处于循环红细胞变形的极限。所采集样本中95%的红细胞能够通过直径为2.9微米的通道。测量的少数毛细血管比这个极限更窄。对六只大鼠的红细胞和毛细血管数据进行了比较。所有六只动物红细胞通过的极限直径非常一致。
