Supplementary Material for: Anatomy, histology, etiology, development and functions of cartilago cordis: A systematic review.

Introduction: The cartilago cordis is a structure present within the cardiac skeleton of some, but not all, vertebrate species. This systematic review compared the presence, structure and function of the cartilago cordis from published works covering all vertebrate species. Methods: Literature searches were conducted to obtain information relating to the anatomical location, morphology, prevalence, number of structures, development and function. Results: The cartilago cordis was most commonly composed of hyaline cartilage but its location within the cardiac skeleton, anatomical and histological structure varied between species. The cartilago cordis has not been documented in every vertebrate species, or every individual within each species, but it is present in 68 vertebrates including an amphibian, and some mammals, reptiles and birds. The function of the cartilago cordis is unknown, but theories have ranged from an adaptive mechanism to support cardiac tissue through to roles in conduction and contraction, especially in areas of high mechanical stress. Possible links between the presence of a cartilago cordis and cardiac pathologies were also identified. Conclusion: The cartilago cordis varied in prevalence, structure, and location; further research is required to understand the function and development. In addition, it is possible there are more vertebrate species containing cartilago cordis than presently known about given its varying prevalence and sometimes small size.