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

该项目使用一种先进的计算机模拟方法，研究了头骨灵活性在蜥蜴进食中的作用。在新生的人类婴儿中，软组织区域保留在头盖骨之间，从而允许灵活性和持续生长。在成人，缝合线关闭，大脑被包裹在坚硬的骨壳中，面部骨骼被固定地附着在上面。Gape是有限的。然而，在成年蜥蜴、蛇和鸟类的头骨中，一些缝合线保持开放，允许头骨部分相互移动。这种灵活性可能是惊人的，例如，在一只吞食身体直径是其头部几倍的大型蛇的猎物中。这种头骨的运作方式显然与哺乳动物的僵硬头骨截然不同，反映了生物学和生活方式上的重大差异。颅骨类型之间的比较研究对于揭示正常、病理和衰老的颅骨功能具有重要意义。哺乳动物需要有规律的食物供应来维持恒定的体温。他们的头骨已经进化到最大限度地提高了口腔食物处理(咀嚼)的效率(例如，分化的牙齿、精确的咬合、坚硬的上颚、精确的肌肉控制)。相比之下，蜥蜴和蛇从外部来源取暖，可以机会性地进食。一顿大餐可以让蛇吃上几个月)，而且通常很少有口腔食物加工。相反，高级蛇的头骨允许更多的张口，并有助于食物通过嘴巴和吞咽。从蛇进化而来的蜥蜴，情况就不那么明确了。头骨的运动更加微妙，它们通过哪些关节起作用，或可能通过哪些关节起作用，目前还不是很清楚。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)不同的头骨部分如何相互移动，移动多少(被动调整或主动关联移动)？C)膜-软骨脑在成人中的作用是什么？它是有助于运动还是限制运动？观察到的解剖变异是否与运动模式相匹配？D)运动对头骨的功能和稳定性有什么影响，这与饮食有何关系？E)运动能力可以通过头骨形状来预测吗？到目前为止，大多数关于蜥蜴运动的讨论都是基于解剖、对死亡或麻醉的动物的操纵、理论分析和少数实验研究。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/进化论；生物力学工程学；形状与功能的分析)。我们有着良好的记录，并开创了一种结合使用3-D计算机模拟(多体动力学分析)和应力分析(有限元分析)的方法。这产生了详细的、解剖学上准确的动物头骨的工作计算机模型，包括关节和肌肉(颌骨、颈部)。然后，复杂的软件可以让我们将头骨形状的变化与进食过程中的头骨表现联系起来。与活动物的比较(咬合力数据，肌肉动作和进食的记录)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)将在新项目中收集更多比较数据。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)、整个英国科学基础(通过跨学科框架对年轻科学家的培训、吸引留学生和合作者、让年轻人参与科学)、更广泛的公众(公众参与、媒体兴趣)，以及潜在的临床医生(对正常、衰老和病理的颅骨、颌骨和牙齿功能的看法)。

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).