Aortic cartilage in the heart of Syrian hamsters

A C‐shaped bar of hyalin cartilage was present in the fibrous tissue around the aortic orifice in the heart of all 70 male and 10 female Syrian hamsters, 103 to 843 days old. This cartilage has the same cellular and intercellular characteristics as the tracheal cartilages. Fibers from four of the six lunulae of the semilunar aortic valves, the aortic sinuses and vestibule, and cardiac muscle adjacent to the posterior semilunar valve insert onto the fibrous capsule and the protuberances of the aortic cartilage. A few fibers from the ventricular and interatrial septa and the aortic cusp of the mitral valves are also attached to the fibrous capsule. Cartilage did not occur around the pulmonary orifice or in other regions of the heart with the exception of a chondroma in the aortic valve. The C‐shaped aortic cartilage in this hibernating species is discussed in relation to its possible significance in preventing collapse of the aortic orifice and the possibility of increasing coronary blood flow.