Three dimensional analysis for collagen fiber orientation in the human lung to investigate how the lung can maintain its structure under mechanical load by respiration.

1)吸气对人体肺部形状的改变，垂直方向的变化大于其他方向。结果表明，吸气时人体肺部垂直方向的机械负荷大于其他方向的机械负荷。2)冠状板胶原纤维取向垂直，纤维取向程度高。但在水平板中，定向较差。3)在冠状板中，特别是在上瓣，垂直方向的机械应力大于水平方向的机械应力。4)胶原纤维取向以水平方向为主，机械应力以垂直方向为主。5)拼贴纤维取向的各向异性与力学应力的各向异性呈负相关。综上所述，人体肺具有各向异性的力学特性，可以在呼吸各向异性的机械负荷下维持其结构。人体肺的力学性能与胶原纤维取向密切相关。

1) Concerning as changes in shapes of human lung by inspiration, those in perpendicular direction were lager than those in other directions. This result suggests that perpendicular mechanical loads to the human lung under inspiration are larger than those of other directions. 2) In coronal plate, collagen fiber orientations were perpendicularly orientated with high degree of fiber orientation. However in horizontal plate the orientations were poorly orientated. 3) In coronal plate, especially on upper lobe, mechanical stresses in perpendicular direction were larger than those in horizontal direction. 4) In collagen fiber orientations, horizontal directions were predominant, while in mechanical stresses, perpendicular directions were predominant. 5) Anisotropy in collage fiber orientation was inversely correlated with that in mechanical stresses.In conclusion, the human lung has anisotropic mechanical properties to maintain its structure under anisotropic mechanical load by respiration. The mechanical properties of the human lung are closely related with collagen fiber orientation.