Yu Q, Zhou J, Fung Y C
Department of Applied Mechanics and Engineering Sciences-Bioengineering, University of California, San Diego, La Jolla 92093-0412.
Am J Physiol. 1993 Jul;265(1 Pt 2):H52-60. doi: 10.1152/ajpheart.1993.265.1.H52.
With few exceptions, experimental results on the blood vessel elasticity have been analyzed with the blood vessel wall treated as a homogeneous material, probably because the experiments have been limited to inflation and stretching. To advance the subject, we must evaluate the force-deformation relationship of different layers of the vessel. A key strategy to do this is to study nonaxisymmetric deformation of the vessel wall so that the different layers of the vessel may deform in different amounts at different places. One of the most effective nonaxisymmetric deformations that can be imposed on the vessel wall is bending. The first important question to ask about bending is, Where is the neutral axis? In this study, a method to determine the neutral axis is presented. We found that the neutral axis of the aorta of the pig lies in the medial layer about one-third of the wall thickness from the endothelium. We measured the strain distribution in the vessel wall by optical methods. Using the load-deflection relationship, we evaluated the Young's modulus of the intima-media layer and that of the adventitia. They differ by an order of magnitude. Our results show that the Young's modulus of the intima-media layer of the pig thoracic aorta is 43.2 +/- 15.8 kPa, whereas the Young's modulus of the adventitial layer is 4.70 +/- 1.72 kPa, in a linear range of the stress-strain relationship including the zero-stress state and the no-load state.
除少数例外情况外，关于血管弹性的实验结果一直是在将血管壁视为均质材料的情况下进行分析的，这可能是因为实验仅限于血管的膨胀和拉伸。为了推动该领域的发展，我们必须评估血管不同层的力-变形关系。实现这一目标的一个关键策略是研究血管壁的非轴对称变形，以便血管的不同层在不同位置可能发生不同程度的变形。可以施加在血管壁上的最有效的非轴对称变形之一是弯曲。关于弯曲要问的第一个重要问题是，中性轴在哪里？在本研究中，提出了一种确定中性轴的方法。我们发现猪主动脉的中性轴位于中膜层，距内皮约为壁厚的三分之一处。我们通过光学方法测量了血管壁中的应变分布。利用载荷-挠度关系，我们评估了内膜-中膜层和外膜层的杨氏模量。它们相差一个数量级。我们的结果表明，在包括零应力状态和无载荷状态在内的应力-应变关系的线性范围内，猪胸主动脉内膜-中膜层的杨氏模量为43.2±15.8 kPa，而外膜层的杨氏模量为4.70±1.72 kPa。
