The left atrioventricular ring is closely connected, by its right margin, with the aortic arterial ring; between these and the right atrioventricular ring is a triangular mass of<unk>  tissue, the<unk> , which represents the os cordis seen in the heart of some of the larger animals, as the ox and elephant.
Fibrous trigone
Plexus
Crista terminalis
Ganglion impar
Commissural fibers
Ducts of Cuvier
Ganglion
Internal arcuate fibers