Anatomical characteristics of brachial plexus in sloths (Bradypus variegatus, SCHINZ, 1825).
brachial plexus, nerve, forelimb, Bradypus variegatus
Bradypus variegatus is a peculiar mammal with wide distribution throughout Brazil, which facilitates its application as a biological model for several studies, including anatomical studies. Defining the morphological aspects is fundamental for the study of evolutionary development and provide baseline for clinical and surgical approaches. The aim of this study was to describe the origin, composition, derived nerves and territory of innervation of the brachial plexus in B. variegatus. Bilateral dissection of the thoracic and spinal cord was performed in 5 formaldehyde 10% adult specimens from the Museu Paraense Emílio Goeldi. The brachial plexus originated from the branches of cervical spinal nerves C6, C7, C8, C9 and C10 and from the thoracic T1 and T2, with grouping of the segments into three trunks: cranial trunk, formed by C6-C8 segments, medium trunk, formed by C9 and the caudal trunk, formed by segments of C10 - T2. These trunks joined together and formed the common trunk that emitted two fascicules: dorsal fasciculus and ventral fasciculus. The main nerves that composed the brachial plexus were the suprascapular, axillary, radial, medial musculocutaneous, cutaneus antebrachii medialis, ulnar, thoracodorsal, long thoracic and subscapular nerves. The long thoracic and suprascapular nerves originated exclusively from the cranial trunk, the thoracodorsal nerve originated in the middle trunk and the other nerves derived from the common trunk. From the dorsal fasciculus the radial and axillary nerves and the ventral fasciculus originated the median musculocutaneous, ulnar and cutaneus antebrachii medialis.