Branches of the aortic arch and thoracic aorta of the sloth (Bradypus variegatus)

ABSTRACT Sloths are arboreal mammals, very specific, regarding their habits and morphology. This condition makes them even more vulnerable to environmental impacts. In order to provide information to assist in the medical and surgical assistance to these Xenarthras, a study of the aortic arch and thoracic portion of the descending aorta was carried out with the purpose of identify its main branches. Ten animals of the Bradypus variegatus species were used. One female and three males were submitted to dissection, where measurements of vessel diameter and length were obtained, while three females and three males were submitted to the digital contrast x-ray technique. There was a uniform syntopy of the arch, as well as of the descending portion of the aorta in the thorax. However, the topography differs considerably. Based on the branches, regardless of gender, a greater variation was observed in those originating from the arch, and those that emerge from the thoracic aorta and irrigate medial structures and the right antimere of the thorax. Greater values were obtained for the diameter of the arteries in the female than in the males and corresponding values for the length of the thoracic aorta in both. All this variation is possibly related to the adaptive processes of Bradipodidae over time.

摘要：树懒是树栖哺乳动物，其习性与形态均具有高度特异性，这使得它们更易受到环境变化的影响。为给这类异关节总目（Xenarthra）动物的医疗与外科救助提供参考依据，本研究针对主动脉弓（aortic arch）与胸段降主动脉（thoracic portion of the descending aorta）开展研究，以明确其主要分支结构。
本研究共纳入10只褐喉树懒（Bradypus variegatus）作为实验对象：其中1雌3雄通过解剖获取血管直径与长度的测量数据，另有3雌3雄采用数字造影X射线（digital contrast X-ray）技术开展观测。
研究结果显示，主动脉弓与胸腔内降主动脉的解剖位置均保持一致，但二者的局部解剖形态存在显著差异。从分支特征来看，无论性别如何，起源于主动脉弓的分支，以及起自胸主动脉并为胸腔内侧结构与右侧镜像体节供血的分支，均存在更为显著的变异。
雌性个体的动脉直径均值显著高于雄性，而二者的胸主动脉长度则无明显差异。上述所有变异特征可能与树懒科（Bradypodidae）长期的适应性演化过程相关。