Jung Jae-Young, Naleway Steven E, Yaraghi Nicholas A, Herrera Steven, Sherman Vincent R, Bushong Eric A, Ellisman Mark H, Kisailus David, McKittrick Joanna
Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA.
Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA.
Acta Biomater. 2016 Jun;37:1-13. doi: 10.1016/j.actbio.2016.03.030. Epub 2016 Mar 18.
Woodpeckers avoid brain injury while they peck at trees up to 20Hz with speeds up to 7m/s, undergoing decelerations up to 1200g. Along with the head, beak and neck, the hyoid apparatus (tongue bone and associated soft tissues) is subjected to these high impact forces. The shape of the hyoid apparatus is unusual in woodpeckers and its structure and mechanical properties have not been reported in detail. High-resolution X-ray micro-computed tomography and scanning electron microscopy with energy dispersive X-ray spectroscopy were performed and correlated with nanoindentation mapping. The hyoid apparatus has four distinct bone sections, with three joints between these sections. Nanoindentation results on cross-sectional regions of each bone reveal a previously unreported structure consisting of a stiff core and outer, more compliant shell with moduli of up to 27.4GPa and 8.5GPa, respectively. The bending resistance is low at the posterior section of the hyoid bones, indicating that this region has a high degree of flexibility to absorb impact. These new structural findings can be applied to further studies on the energy dissipation of the woodpecker during its drumming behavior, and may have implications for the design of engineered impact-absorbing structures.
Woodpeckers avoid brain injury while they peck at trees, which results in extreme impact conditions. One common adaptation in woodpeckers is the unusual shape of the elongated tongue, also called the hyoid apparatus. The relationship between the structure and mechanical properties of the bony part of the hyoid apparatus has not been previously reported. A three dimensional model of the bony tongue was developed, and the hardness and stiffness were evaluated. A new type of bone structure, which is opposite of typical skeletal bone structure was found. The combined microstructural and mechanical property analysis indicate possible energy absorption routes for the hyoid apparatus and are applicable to the design of engineered structures.
啄木鸟以高达20赫兹的频率、高达7米/秒的速度啄树，承受高达1200g的减速度，却能避免脑损伤。除头部、喙和颈部外，舌骨装置（舌骨及相关软组织）也会受到这些高冲击力。啄木鸟的舌骨装置形状独特，其结构和力学性能尚未得到详细报道。我们进行了高分辨率X射线显微计算机断层扫描以及带有能量色散X射线光谱的扫描电子显微镜检查，并与纳米压痕测绘相关联。舌骨装置有四个不同的骨段，这些骨段之间有三个关节。对每块骨的横截面区域进行纳米压痕测试的结果显示出一种此前未报道过的结构，该结构由一个坚硬的核心和外部更具柔韧性的外壳组成，其模量分别高达27.4GPa和8.5GPa。舌骨后部的抗弯性较低，表明该区域具有高度的柔韧性以吸收冲击力。这些新的结构发现可应用于对啄木鸟啄木行为中能量耗散的进一步研究，并且可能对工程抗冲击结构的设计有启示意义。
啄木鸟啄树时能避免脑损伤，这会产生极端的冲击条件。啄木鸟的一个常见适应性特征是其细长舌头（即舌骨装置）的独特形状。此前尚未报道过舌骨装置骨质部分的结构与力学性能之间的关系。我们构建了舌骨的三维模型，并评估了其硬度和刚度。发现了一种与典型骨骼结构相反的新型骨结构。微观结构和力学性能的综合分析表明了舌骨装置可能的能量吸收途径，并且适用于工程结构的设计。
