Aspectos anatômicos do plexo lombossacral de Myrmecophaga tridactyla (Linnaeus, 1758)

Abstract

This study aimed to describe the origin and architecture of the lumbosacral plexus, as well as the composition of their nerves in the species M. tridactyla. For this purpose, 12 plexuses from six adult animals of both sexes, provided by IBAMA-GO (License 99/2011, CEUA-UFG Protocol 015/11) were analyzed. The ventral rami of the spinal nerves, their communications and the nerves arising from the plexus were detected after the dissection of the ventral face of the thoracic caudal, lumbar and sacral regions. The radiographs showed 15 or 16 thoracic, two or three lumbar and four or five sacral vertebrae. The lumbosacral plexus of M. tridactyla consisted of: T16, L1, L2, S1-S5, Cc1 (33.3%); T15, L1- L3, S1-S5 (16.6%); T15, L1, L2, S1-S5, Cc1 (16.6%); L1-L3, S1-S5 (16.6%); T15, L1-L3, S1-S4, Cc1 (8.3%); and L1-L3, S1-S4 (8.3%). The nerves that derived from the plexus with their most common arrangement were: genitofemoral (T15, L1, L2; and T16, L1); lateral femoral cutaneous nerve (T15, L1, L2; and T16, L1); femoral (T16, L1, L2); obturator (L1- L3); sciatic (L3, S1-S3); cranial gluteal (L2, S1, S2); caudal gluteal (L2, S1-S3; and L3, S1, S2); pudendal (S4, S5); and rectal caudal (S5 and S4, S5, Cc1). The caudal femoral cutaneous nerve originated from the sciatic nerve. In general, the lumbosacral plexus of M. tridactyla resembles that of other mammals; however, it shows some peculiarities, such as the involvement of thoracic and coccygeal rami in its nerve composition and a greater anatomical variation in its formation, which can be mainly related to the numerical variation of thoracic, lumbar and sacral vertebrae in this species.