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

骨组织在个体的一生中适应和变化，最好的证明是骨重建的过程。骨重建和重建组织的组织学分析是现代医学和法医学的焦点，因为它们在人类骨发育中的重要性。在重塑过程中发育的组织被称为次生骨，因为它们取代了动物最初生长过程中形成的原生骨。在皮质骨中，重塑产生次级骨单位，如果它们完全取代初级骨，则称为哈弗氏骨。次生骨单位和哈弗氏骨在许多恐龙中被观察和描述，特别是非鸟类恐龙，真兽目哺乳动物和鸟类。哈弗氏骨多见于大型吸热动物。然而，没有对原因作出充分的解释。在现存的哺乳动物，特别是人类中，已经被援引来解释哈弗氏骨的其他因素，如疲劳损伤、机械负荷和生理学，都在骨重建中发挥作用。但是，这些因素中的每一个的重要性和对组织学的影响还有待于从涉及蜥脚类动物，特别是恐龙和鸟类的比较角度详细探讨。骨化石的组织学研究主要集中在原生骨的组织学研究上，对已灭绝生物的次生骨缺乏详细的分析和比较。该项目旨在通过从比较和进化的角度探讨问题，提高对哈弗氏骨形成和组织学水平上骨重建过程的理解，使用广泛的已灭绝和现存的骨化石。恐龙在这一比较中特别重要，因为它们是唯一可与哺乳动物进行比较的大型温血陆地动物。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，我们将试图回答不同的因素如何影响哈弗氏骨发育，并解释观察到的皮质骨重建模式。该项目的优势在于利用化石记录中的数据来了解现存动物（包括人类）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.