The role of skull flexibility in feeding - an investigation using advanced computer modelling techniques

该项目利用先进的计算机建模方法，研究了头骨灵活性在蜥蜴进食中的作用。在人类新生婴儿中，软组织区域保留在头骨之间，允许灵活性和持续生长。在成年人中，脑缝闭合，大脑被封闭在坚硬的骨壳中，面骨固定不动地附着在该骨壳上。Gape是有限的。然而，在成年蜥蜴、蛇和鸟类的头骨中，一些缝合处仍然是开放的，允许头骨部分彼此移动。这种灵活性（=运动）可以是壮观的，例如，在一条大蛇吞下猎物的身体直径是自己头部的几倍。这种头骨的运作方式显然与哺乳动物的刚性头骨非常不同，反映了生物学和生活方式的重大差异。颅骨类型之间的比较研究在揭示正常、病理和老化颅骨功能方面具有重要意义。哺乳动物需要有规律的食物供应来维持恒定的高体温。他们的头骨已经进化到最大限度地提高口腔食物处理（咀嚼）的效率（例如分化的牙齿，精确的咬合，硬腭，精确的肌肉控制）。相反，蜥蜴和蛇从外部来源温暖自己，并可以伺机而动。一顿大餐可以持续一条蛇几个月），通常很少有口服食品加工。相反，高级蛇的头骨允许增加张口，并帮助食物通过口腔运输和吞咽。在蛇的进化者蜥蜴身上，情况就不那么明确了。头骨的运动更为微妙，许多关节通过它们的行为，或潜在的行为，没有得到很好的理解。许多问题仍然没有答案，特别是：a）哪些蜥蜴真的是能动的，在多大程度上？B）不同的颅骨部分如何相对于彼此移动，移动多少（被动调整或主动联动运动）？c）膜软骨脑囊在成人中的作用是什么？它是否有助于或限制运动？观察到的解剖变异是否与室壁运动模式相匹配？d）运动对颅骨功能和稳定性的影响是什么，这与饮食有什么关系？e）运动能力可以通过头骨形状预测吗？迄今为止，大多数关于蜥蜴运动的讨论都是基于解剖、对死亡或麻醉动物的操纵、理论分析和一些实验研究。因此，在许多问题上缺乏一致意见。先进的计算机建模提供了另一种方法。我们的研究小组是跨学科的（爬行动物解剖学/进化;生物力学工程;形状与功能的关系分析）。我们拥有强大的跟踪记录，并率先采用了将三维计算机模拟（多体动力学分析）和应力分析（有限元分析）相结合的方法。这产生了详细的、解剖学上精确的动物头骨工作计算机模型，包括关节和肌肉（下巴、脖子）。然后，复杂的软件使我们能够将改变头骨形状与喂养过程中的头骨性能联系起来。与活体动物的比较（咬合力数据，肌肉动作和进食记录）表明我们的模型在生物学上是真实的，但我们的美国合作者（Ross，Lappin）将在新项目中收集进一步的比较数据。我们工作的受益者包括学术界（进化生物学家，古生物学家，功能解剖学家-数据和新的方法论方法），英国科学基础一般（通过在跨学科框架内培训青年科学家，吸引海外学生和合作者，让青年人参与科学），（公众参与，媒体的兴趣），并可能，临床医生（正常，老化和病理头骨，颌骨和牙齿功能的观点）。

The project examines the role of skull flexibility in lizard feeding, using an advanced computer modelling approach. In a newborn human baby, areas of soft tissue remain between skull bones, allowing flexibility and continued growth. In an adult, the sutures close and the brain is enclosed in a rigid bony shell to which the facial bones are immovably attached. Gape is limited. However, in the skulls of adult lizards, snakes and birds some sutures remain open, allowing movement of the skull parts on one another. This flexibility (=kinesis) can be spectacular, e.g. in a large snake swallowing prey with a body diameter several times that of its own head. Such skulls clearly operate in a very different way to the rigid skulls of mammals, and reflect major differences in biology and lifestyle. Comparative studies between skull types are important in shedding light on normal, pathological and aging skull functions generally. Mammals need a regular supply of food to maintain a constant high body temperature. Their skulls have evolved to maximise the efficiency of oral food processing (chewing) (e.g. differentiated teeth, precise occlusion, hard palate, precise muscle control). Lizards and snakes, in contrast, warm themselves from external sources and can feed opportunistically. A large meal can last a snake for months), and there is usually little oral food processing. Instead, the skull of advanced snakes allows increased gape and aids both food transport through the mouth and swallowing. In lizards, from which snakes evolved, the situation is less clear-cut. Skull movements are more subtle and many of the joints through which they act, or potentially act, are not well understood. Many questions remain unanswered, notably: a) which lizards are really kinetic and to what degree? b) how do the different skull parts move in relation to one another, and by how much (passive adjustments or active linked movements)? c) what is the role of the membrane-cartilage braincase in the adult? Does it aid or limit kinesis? Does observed anatomical variation match the pattern of kinesis? d) what are the consequences of kinesis for skull function and stability, and how does this relate to diet? e) can kinetic ability be predicted by skull shape? To date, most discussion of lizard kinesis has been based on dissection, manipulation of dead or anaesthetised animals, theoretical analyses, and a few experimental studies. As a result, there is a lack of agreement on many points. Advanced computer modelling offers an alternative approach. Our research group is cross-disciplinary (reptile anatomy/evolution; biomechanical engineering; analysis of shape in relation to function). We have a strong track-record and have pioneered an approach that combines the use of 3-D computer simulations (multibody dynamics analysis) and stress analysis (finite element analysis). This yields detailed, anatomically accurate working computer models of animal skulls, including joints and muscles (jaw, neck). Sophisticated software then allows us to relate changing skull shape to skull performance during feeding. Comparisons with living animals (bite force data, records of muscle action and feeding) have shown our models to be biologically realistic, but our U.S collaborators (Ross, Lappin) will collect further comparative data in the new project. Beneficiaries of our work include the academic community (evolutionary biologists, palaeontologists, functional anatomists - data and new methodological approaches), the UK science base in general (through training of young scientists in an interdisciplinary framework, attraction of overseas students and collaborators, engaging young people in science), the wider public (public engagement, media interest) and, potentially, clinicians (perspectives on normal, aging and pathological skull, jaw and tooth function).