Department of Bioscience, Zoophysiology, Aarhus University, Aarhus C 8000, Denmark; Department of Anatomy, Embryology & Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, 1105, The Netherlands.
Biol Rev Camb Philos Soc. 2014 May;89(2):302-36. doi: 10.1111/brv.12056. Epub 2013 Sep 2.
With approximately 7000 species, snakes and lizards, collectively known as squamates, are by far the most species-rich group of reptiles. It was from reptile-like ancestors that mammals and birds evolved and squamates can be viewed as phylogenetically positioned between them and fishes. Hence, their hearts have been studied for more than a century yielding insights into the group itself and into the independent evolution of the fully divided four-chambered hearts of mammals and birds. Structurally the heart is complex and debates persist on rudimentary issues such as identifying structures critical to understanding ventricle function. In seeking to resolve these controversies we have generated three-dimensional (3D) models in portable digital format (pdf) of the anaconda and anole lizard hearts ('typical' squamate hearts) and the uniquely specialized python heart with comprehensive annotations of structures and cavities. We review the anatomy and physiology of squamate hearts in general and emphasize the unique features of pythonid and varanid lizard hearts that endow them with mammal-like blood pressures. Excluding pythons and varanid lizards it is concluded that the squamate heart has a highly consistent design including a disproportionately large right side (systemic venous) probably due to prevailing pulmonary bypass (intraventricular shunting). Unfortunately, investigations on rudimentary features are sparse. We therefore point out gaps in our knowledge, such as the size and functional importance of the coronary vasculature and of the first cardiac chamber, the sinus venosus, and highlight areas with implications for vertebrate cardiac evolution.
蛇和蜥蜴（统称为有鳞目）有大约 7000 个物种，是目前为止爬行动物中物种最丰富的群体。哺乳动物和鸟类是从类似爬行动物的祖先进化而来的，有鳞目可以被视为它们与鱼类之间的进化分支。因此，人们对它们的心脏进行了一个多世纪的研究，从而深入了解了这一类群本身，以及哺乳动物和鸟类完全分隔的四腔心脏的独立进化。从结构上看，心脏非常复杂，关于识别对理解心室功能至关重要的结构等基本问题的争论仍在持续。为了解决这些争议，我们以便携式数字格式（pdf）生成了水蚺和安乐蜥心脏（“典型”有鳞目心脏）以及独特的特化巨蟒心脏的三维（3D）模型，并对结构和腔室进行了全面注释。我们综述了有鳞目心脏的解剖和生理学，并强调了蟒蛇和巨蜥心脏的独特特征，这些特征赋予了它们类似哺乳动物的血压。不包括蟒蛇和巨蜥，结论是有鳞目心脏具有高度一致的设计，包括不成比例的右侧（体循环静脉），这可能是由于普遍存在的肺循环（心室内分流）所致。不幸的是，关于基本特征的研究很少。因此，我们指出了我们知识中的空白，例如冠状脉管系统和第一个心脏腔室，腔静脉窦的大小和功能重要性，并强调了与脊椎动物心脏进化相关的领域。
