Cortical bone remodeling and Haversian bone in amniotes: a deep-time and comparative perspective

骨组织在人的一生中不断适应和变化，这在骨重建过程中得到了最好的证明。骨改建和改建组织的组织学分析是现代医学和法医学研究的焦点，因为它们在人类骨骼发育中具有重要意义。在重塑过程中形成的组织被称为次级骨，因为它们取代了动物在最初生长过程中形成的初级骨。在皮质骨中，如果次级骨完全取代初级骨，重塑就会产生次级骨，称为哈弗斯骨。次级骨和哈弗斯骨在许多羊膜动物，特别是非鸟类恐龙、真兽类和鸟类中被观察和描述。哈弗斯骨更多地出现在大型吸热动物身上。然而，对于原因还没有提供足够的解释。其他被引用来解释现存哺乳动物，特别是人类的哈弗斯骨的因素，如疲劳损伤、机械负荷和生理学，都在骨重建中发挥作用。但这些因素的重要性和对组织学的影响尚未从蜥蜴类，特别是恐龙和鸟类的比较角度进行详细探讨。化石骨组织学研究一般集中在原生骨组织学上，缺乏对已灭绝类群中的次生骨进行详细的分析和比较。这个项目的目的是通过从比较和进化的角度解决这个问题，从组织学水平上提高对哈弗斯骨的形成和骨重建过程的理解，使用广泛的羊膜动物，包括灭绝的和现存的。恐龙在这一比较中尤为重要，因为它们是唯一可以与哺乳动物进行比较的大型体型和可能是温血的陆地动物。通过考虑不同的生活方式、生活史、运动模式、食物来源和生理机制，我们将试图回答不同因素如何影响哈弗斯骨的发育，并解释观察到的皮质骨重塑模式。这个项目的优势在于使用化石记录中的数据来了解包括人类在内的现存动物骨骼生物学的普遍特征。

Bone tissue adapts and changes through the lifetime of an individual, best demonstrated by the process of bone remodeling. Bone remodeling and histological analysis of remodeled tissue are in the focus of modern medical and forensic science because of their importance in human bone development. The tissues that develop during remodeling are called secondary bone because they replace the primary bone laid down during the initial growth of the animal. In cortical bone, remodeling produces secondary osteons which are called Haversian bone if they completely replace the primary bone. Secondary osteons and Haversian bone have been observed and described in many amniotes, particularly non-avian dinosaurs, eutherian mammals, and birds. Haversian bone is present more in large, endothermic animals. However, no sufficient explanation has been offered as to the cause. Other factors that have been invoked to explain Haversian bone in extant mammals, particularly humans, such as fatigue damage, mechanical loading and physiology all play a role in bone remodeling. But the importance and influence on histology of each of these factors has yet to be explored in detail from a comparative perspective involving sauropsids, particularly dinosaurs, and birds. Studies in histology of fossil bone generally focus on primary bone histology, and thus, there is lack of detailed analyses and comparisons of secondary bone in extinct taxa. This project aims to improve the understanding of the formation of Haversian bone and the process of bone remodeling at the histological level by approaching the problem from a comparative and evolutionary perspective, using a broad range of amniotes, extinct and extant. Dinosaurs are particularly important in this comparison because they are the only large-bodied and presumably warm-blooded land animals available for comparison with mammals. By taking the different life styles, life histories, locomotory patterns, food sources and physiologies into account, we will attempt to answer how different factors influence Haversian bone development and explain the observed patterns in cortical bone remodeling. The strength of this project is the use of data from the fossil record to understand a pervasive feature of the bone biology of extant animals, including humans.