Witzel U, Preuschoft H, Sick H
Forschungsbereich Biomechanik, Fakultät für Maschinenbau, Ruhr-Universität Bochum, Bochum, Germany.
Folia Primatol (Basel). 2004 Jul-Aug;75(4):202-18. doi: 10.1159/000078935.
The zygomatic arch of mammals is usually considered a phylogenetic relic of the fenestrations of the skull roof which may be observed in morphological sequences of primitive vertebrate skulls. If this concept is correct, the element is comparable (though not homologous) to the jugal arches of diapsid reptiles. Two major questions then remain unanswered: why different elements are maintained in reptiles and mammals during evolution, and why the arches are maintained as relics of ancestral forms. It is tempting to respond to the latter question with a very simple answer, namely that the elements function in order to sustain mechanical stresses. In this paper, we raise the questions which quality of stresses occurs in a primate skull within the zygomatic arches and what relationship these stresses hold to the morphology of these bony elements. An answer has been sought by means of finite element stress analysis. We found that the zygomatic arch in primate skulls represents a structure which carries, under all biologically relevant conditions, either compressive or tensile stresses. In a very simple model of the human skull under bite forces, a strip of stresses occurs lateral to the orbits, which seems roughly comparable to the zygomatic arch. Once such a structure exists and is used as an insertion of adductor muscles, it will be exposed to bending stress in side view and in frontal view. Morphological details of the zygomatic arch (curvature, profile, suture) are well suited to sustain the evoked stresses by a minimum of material.
哺乳动物的颧弓通常被认为是颅顶开孔的系统发育遗迹，在原始脊椎动物头骨的形态序列中可以观察到这种开孔。如果这个概念是正确的，那么这个结构（尽管并非同源）与双孔类爬行动物的眶后弓具有可比性。那么，仍然有两个主要问题没有答案：为什么在进化过程中，爬行动物和哺乳动物保留了不同的结构，以及为什么这些弓作为祖先形态的遗迹被保留下来。对于后一个问题，人们很容易给出一个非常简单的答案，即这些结构的功能是为了承受机械应力。在本文中，我们提出了这样的问题：在灵长类动物头骨的颧弓内会出现何种性质的应力，以及这些应力与这些骨结构的形态有什么关系。我们通过有限元应力分析来寻找答案。我们发现，灵长类动物头骨中的颧弓代表了一种结构，在所有生物学相关条件下，它承受的要么是压应力，要么是拉应力。在一个非常简单的人类头骨咬合力模型中，眼眶外侧会出现一条应力带，这似乎大致与颧弓相当。一旦这样的结构存在并被用作内收肌的附着点，从侧视图和正视图来看，它都会受到弯曲应力。颧弓的形态细节（曲率、轮廓、缝合线）非常适合用最少的材料来承受所产生的应力。
