Macroscopic anatomy of the heart and respiratory system of the grasscutter (Thryonomys swindérianus, Temminck, 1827)

Abstract Background The grasscutter is the second-largest rodent of scientific interest in Africa. This study describes the macroscopic anatomy of the grasscutter’s heart and lower respiratory tract. Results The heart of the large grasscutter is globular in shape, has a moderately obtuse apex, and weighs 21.92 ± 5.69 g. It projects between the second and fifth ribs. It represents 0.66% of live weight. The right cavities are larger than the left, although their walls are thinner. The right atrium receives the cranial (bifurcated) and caudal vena cava. The aorta gives rise to the brachiocephalic trunk, which divides into the right common carotid artery and the right subclavian artery; the left subclavian artery arises directly from the aorta. The common carotid arteries arise from a bicarotid trunk. The right atrioventricular valve has three cusps, two of which appear fused; the left valve is bicuspid, with a dominant septal cusp. The left subauricular papillary muscle is more developed, and the aortic valve has three semilunar valves. The respiratory system consists of a trachea made up of approximately thirty C-shaped cartilaginous rings that extend from the larynx to the point where it divides into the right and left main bronchi. The right lung is divided into four lobes cranial, middle, caudal, and accessory separated by interlobar fissures. The left lung consists of cranial and caudal lobes, which are also separated by interlobar fissures. The caudal lobe has a distinct medial segment. The lobation of the right and left lungs was verified by bronchography. Conclusion These anatomical data will contribute to a better understanding of the biology of the grasscutter for possible application in veterinary medicine.