First Confirmed Histological and High-Resolution X-Ray Computed Microtomography Characterization of Multiple Ossa...

Heterotopic bones that are within the cardiac skeleton are termed ossa cordis. This is the first confirmed ossa cordis in nyala (Tragelaphus angasii). Three distinct bones (two dextrum and one sinistrum) were discovered, a novel finding in any species. The present research used high-resolution X-ray computed microtomography, hematoxylin, and eosin, Picrosirius red, Masson's trichrome, Alcian blue, Von Kossa, immunohistochemistry, and a phylogenetic tree to investigate ossa cordis. The structural morphology and anatomical investigations showed the novel features of the three bones: one ossa cordis dextrum, one ossa cordis sinistrum, and one additional lower ossa cordis, on the right side of the trigone classified as ossa cordis dextrum inferus. The histological studies confirmed trabeculation, bone marrow, vasculature, collagen types I and III, in addition to acid mucins in the ossa cordis. The cell types within the three ossa cordis, and the associated cartilage, were also described. The discovery of cartilage adjacent to ossa cordis in this, and other species, may help elucidate the process, possibly endochondral ossification, via which ossa cordis may develop. The novel discovery of two ossa cordis dextrum and one ossa cordis sinistrum, and the first histological and computed microtomography study about ossa cordis in the nyala, increases the knowledge about ossa cordis in general and within this species. Although there is much to be elucidated regarding the nyala ossa cordis, especially in relation to prevalence, this study identifies the 23rd species with ossa cordis and describes the structural and histological details of these bones and associated cartilage.