Song J, Xu L X, Lemons D E, Weinbaum S
Department of Mechanical Engineering, City College/CUNY, NY 10031, USA.
J Biomech Eng. 1997 Nov;119(4):461-8. doi: 10.1115/1.2798294.
This study was undertaken to gain a better understanding of the countercurrent heat exchange of thermally significant blood vessels in skeletal muscle by measuring the vascular structure and flow in an exteriorized rat spinotrapezius muscle and estimating the enhancement in the effective thermal conductivity of the muscle. Detailed anatomic measurements of the number density and length of countercurrent vessel pairs between 45 and 165 microns diameter were obtained. Moreover, diameter and blood flow in the 1A to 3A vessels were measured for muscles in which pharmacological vasoactive agents were introduced, allowing one to vary the local blood flow Peclet number from 1 to 18 in the major feeding arteries. These combined measurements have been used to estimate the range of possible enhancement in the effective thermal conductivity of the tissue. The newly derived conduction shape factor in Zhu et al. for countercurrent vessels in two-dimensional tissue preparations was used in this analysis. Our experimental data indicated that the value of this conduction shape factor was about one-third to two-thirds the value for two countercurrent vessels of the same size and spacing in an infinite medium. The experiment also revealed that the Weinbaum-Jiji expression for keff was valid for the spinotrapezius muscle when the largest vessels were less than 195 microns diameter. A fivefold increase in keff was predicted for 195 microns diameter vessels. Vasoregulation was also shown to have a dramatic effect on keff. A tissue that exhibits only small increases in keff due to countercurrent convection in its vasoconstricted state can exhibit a more than fivefold increase in keff in its vasodilated state.
本研究旨在通过测量大鼠体外斜方肌中具有显著热效应的血管的逆流热交换情况，测量其血管结构和血流，并估算肌肉有效热导率的增强情况，从而更好地理解骨骼肌中的逆流热交换。获得了直径在45至165微米之间的逆流血管对的数量密度和长度的详细解剖学测量结果。此外，对于引入了药理血管活性药物的肌肉，测量了1A至3A血管的直径和血流，从而能够在主要供血动脉中将局部血流佩克莱数从1变化到18。这些综合测量结果已用于估计组织有效热导率可能增强的范围。本分析中使用了朱等人新推导的二维组织制剂中逆流血管的传导形状因子。我们的实验数据表明，该传导形状因子的值约为无限介质中相同尺寸和间距的两个逆流血管的值的三分之一至三分之二。实验还表明，当最大血管直径小于195微米时，温鲍姆-吉吉关于有效热导率的表达式对斜方肌有效。对于直径为195微米的血管，预测有效热导率会增加五倍。血管调节也被证明对有效热导率有显著影响。一种在血管收缩状态下因逆流对流导致有效热导率仅小幅增加的组织，在血管舒张状态下其有效热导率可能会增加超过五倍。
