Cátedra de Biología General, Facultad de Ciencias Naturales e IML, UNT, Miguel Lillo 205, 4000, San Miguel de Tucumán, Argentina.
Instituto de Biodiversidad Neotropical, CONICET- UNT, Horco Molle s/n Yerba Buena, 4107, Tucumán, Argentina.
Biol Rev Camb Philos Soc. 2019 Dec;94(6):2011-2032. doi: 10.1111/brv.12546. Epub 2019 Jul 29.
Along with supernumerary bones, sesamoids, defined as any organized intratendinous/intraligamentous structure, including those composed of fibrocartilage, adjacent to an articulation or joint, have been frequently considered as enigmatic structures associated with the joints of the skeletal system of vertebrates. This review allows us to propose a dynamic model to account for part of skeletal phenotypic diversity: during evolution, sesamoids can become displaced, attaching to and detaching from the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached sesamoids are able to transform into each other, contributing to the phenotypic variability of the tetrapod skeleton. This dynamic model is a new paradigm to delineate the contribution of sesamoids to skeletal diversity. Herein, we first present a historical approach to the study of sesamoids, discussing the genetic versus epigenetic theories of their genesis and growth. Second, we construct a dynamic model. Third, we present a summary of literature on sesamoids of the main groups of tetrapods, including veterinary and human clinical contributions, which are the best-studied aspects of sesamoids in recent decades. Finally, we discuss the identity of certain structures that have been labelled as sesamoids despite insufficient formal testing of homology. We also propose a new definition to help the identification of sesamoids in general. This review is particularly timely, given the recent increasing interest and research activity into the developmental biology and mechanics of sesamoids. With this updated and integrative discussion, we hope to pave the way to improve the understanding of sesamoid biology and evolution.
除了额外骨、籽骨（被定义为任何附着于关节或关节附近的、由纤维软骨组成的有组织的腱内/韧带内结构）以外，人们还经常认为，与脊椎动物骨骼系统的关节相关的神秘结构还有籽骨。这篇综述使我们能够提出一个动态模型来解释部分骨骼表型多样性：在进化过程中，籽骨可能会移位，附着在长骨骨骺和骨干上，然后又与之分离。骨骺、副骨和分离的籽骨可以相互转化，从而为四足动物骨骼的表型多样性做出贡献。这个动态模型是一个新的范例，可以用来描述籽骨对骨骼多样性的贡献。在此，我们首先对籽骨的研究进行了历史性的探讨，讨论了它们的发生和生长的遗传与表观遗传理论。其次，我们构建了一个动态模型。第三，我们对主要四足动物群的籽骨文献进行了总结，包括兽医和人类临床方面的贡献，这是近几十年来籽骨研究最多的方面。最后，我们讨论了某些被标记为籽骨的结构的身份，尽管它们的同源性没有经过充分的正式测试。我们还提出了一个新的定义，以帮助识别一般的籽骨。鉴于最近对籽骨的发育生物学和力学的兴趣和研究活动不断增加，这篇综述具有特别的及时性。通过这次更新和综合的讨论，我们希望为改善对籽骨生物学和进化的理解铺平道路。
