Origens e ramificações do plexo braquial no cachorro-do-mato Cerdocyon thous (Linnaeus, 1766)

Abstract

RESUMO.-Este estudo teve o objetivo de descrever a origem e ramificação dos nervos de vinte plexos braquiais de cachorro-do-mato (Cerdocyon thous). Dez animais da espé-cie, obtidos post mortem por atropelamento em rodovias, foram utilizados para o estudo, de acordo com a autorização do IBAMA/SISBIO nº33667-1. This study aimed to describe the origin and branching of nerves from twenty brachial plexuses of crab-eating foxes (Cerdocyon thous). Ten animals of the species, obtained post mortem from being run over on highways, were used for the study, in accordance with the authorization from IBAMA / SISBIO No. 33667-1. Once collected, the cadavers were fixed in 50% formaldehyde and kept for at least 14 days in a solution of 10% formaldehyde before dissections. After removal of skin, incisions in breast muscles and reflection of thoracic limbs allowed access to axillary space and the nerves could have trajects dissected individually to each muscle insertion. To improve visualization of the cervical and thoracic ventral roots that originated every single nerve, muscles that covered the intervertebral foramina, transverse processes and vertebral bodies were removed ventrally and the spinal cord exposed. Schematic drawings and photographic records documented the origin and branching of nerves. The twenty plexuses were resulted from connections between the ventral branches of the last three cervical spinal nerves (C6, C7 and C8) and first thoracic (T1). These branches derived the nerves suprascapular, subscapular, axillary, musculocutaneous, radial, median and ulnar to the intrinsic muscles and brachiocephalic, thoracodorsal, lateral thoracic, long thoracic, cranial and caudal pectoral nerves to the extrinsic muscles of the thoracic limb. It was found that the ventral rami of C7 were the main contributors in the formation of nerves (61.5%), followed by C8 (55.4%), T1 (41.2%) and C6 (30.8%). The t-test comparison between means at a significance level of 5% showed no differences in the origin of plexus when compared antimeres and sexes. Of the total of 260 dissected nerves, 68.8% originated by the combination of two or three roots, while only 31.2% were formed by a single root. The combination between C8 and T1 was the most frequent origin of nerves to the plexus (23.8%) in this species. Comparing the origin, branching and innervation area of the brachial plexus in C. thous with other domestic and wild species, there was a greater similarity with the domestic dog. These results may give the anatomical basis to diagnosis of neuromuscular disorders, anesthetic blocks techniques and comparative morphofunctional analyzes involving this species.INDEX TERMS: Brachial plexus, morphology, wild carnivores, animal anatomy, Cerdocyon thous.

BRACHIAL PLEXUS IN THE Leopardus geoffroyi

“…The suprascapularis nerve of L. geoffroyi is formed invariably by C6, half of the suprascapularis nerve had contribution of C5. C6 participation in the forming of this nerve occurs in all species of the Carnivora order already described, although C7 frequently contributes instead of C5 for canids (30,31,(33)(34)(35)(36)(37)42) . Fioretto et al (20) have suggested that swimming species would have a suprascapularis nerve with broad plurisegmental origin (with three or even more branches).…”

“…Ventral branches of C7 participated in forming 70.5% of nerves of the L. geoffroyi brachial plexus. Also, it was the branch that most originated the nerves of C. thous (61.5%) (34) and L. gymnocercus (62.7%) (35) . Even though a small number of studies determined the participation percentage of each ventral branch, the findings in L. geoffroyi seems to repeat the anatomic patterns for domestic felids (38) , L. pardalis (31) , domestic dog (30) , M. foina (36) and N. nasua (37) .…”

“…Allam et al (30) determined in their study that only 20.69% of the plexuses of domestic canines were formed between the C5 and T1 branches, illustrating the participation of C5 in forming the brachiocephalicus nerve, as observed for L. geoffroyi. For wild canines (specialised cursorial) such as Atelocynus microtis (33) , Cerdocyon thous (34) and Lycalopex gymnocercus (35) and mustelids such as Martes foina (36) , the brachial plexus was restricted to four segments, being those between the C6 and T1 segments. For the procyonid Nasua nasua that uses the limbs for different functions, the plexus was also formed between the segments C5 and T1 (37) .…”

“…For L. geoffroyi, there was no formation of such trunks, occurring very distinct branches origin, similar to domestic mammals (7) . The absence of the trunk is emphasised for domestic (30) and wild canids (34,35) .…”

Origin and antimeric distribution of brachial plexus nerves inAlouatta guariba clamitansCabrera, 1940 (Primates: Atelidae)

“…majority of the nerves received the contribution of C6 and C7 (Santos-Sousa et al 2016). In the Neotropical canids Cerdocyon thous and Lycalopex gymnocercus, the ventral branches C7 and C8 predominated (Souza-Junior et al 2014, 2017), yet C5 does not take part in the plexus of these species. The suprascapular nerve of other primate species exhibited the participation of C6 almost as a rule, as described in Pongo sp.…”