Anatomical study of the lumbar, sacral, and coccygeal plexuses in monkey (Cebus apella): origin, composition and resulting nerves

Author(s)

Roseâmely Angelica de Carvalho Barros

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2002-10-17

Examining board members

Irvenia Luiza de Santis Prada; Arani Nanci Bomfim Mariana; Zenon Silva

• Advisor: Irvenia Luiza de Santis Prada

Abstract

The non-human primates have been considered an important group among the diverse studied animals, having a great interest not only for the understanding of its own evolution, but also due to the fact that the detailed knowledge of its Anatomy can represent a relevant factor for its preservation and protection. In addition, concerning the neural system, the comparative study on the composition of the lumbo-sacral plexus representing the origin of the nerves that are destined to the pelvic members, shows a particular interest for being an anatomical segment involved in evolutionary aspects of posture and locomotion. The aim of this work was to study the origin, composition and resulting nerves of the lumbar, sacral, and coccygeal plexuses in monkey Cebus apella in order to obtain a better comprehension of the pelvis and pelvic member neural supply in this animal. Previous studies have not demonstrated any findings on the topic in this species. Twenty animals, 10 male and 10 female, were obtained from the conserved anatomical piece collection of the Anatomy Laboratory of the Federal University of Uberlândia. The preparation of the specimens consisted of fixation and dissection according to the routine procedures used in anatomical studies. After a detailed analysis of the specimens, it was verified that the lumbo-sacral-coccygeal plexus of Cebus apella is almost always separated in lumbar, sacral and coccygeal segments. There were considerable variations among the specimens and between the sides. The roots L2 -L5 participated in the formation of the lumbar plexus, with higher frequency of L3 and L4, while the roots L4-S4 and S3-Co3 contributed for the formation of the sacral and the coccygeal plexuses, respectively. The right lumbar plexus was formed by L2, L3, and L4 (75% of cases), L3 and L4 (55%), L2, L3, L4 (20%), and L2, L3, L4 and L5 (5%), while on the left side there was participation of L2, L3, and L4 (80%), being that L3 and L4 (50%) and L2, L3, L4 and L5 (30%), and L5 is present in 15% and L2 and L3 in 5%. The right sacral plexus was constituted of L4-S4; of L4-S2 in 30% of cases; L4-S3 in 25%; L5-S2 in 25%; L5-S3 in 10%, and 10% other occurrences, while on the left side the sacral plexus was formed by the union of L4-S3 in 80% of cases, being that 35% received contribution of L4-S2, L4-S3 in 25%; L5-S2 in 15% and L5-S4 in 5%. The coccygeal plexus is consisted of branches from S3 to Co3, being that in 65% the cranial end is S3 and in 35% is S4. The number of anastomoses is variable in any of the three plexuses. The sympathetic trunk is present and contains five or six ganglions, each one with its grayish communicant branch. The resulting nerves from the lumbar plexus are: cutaneous femoris lateralis, femoralis and obturatorius; from the sacral plexus: ischiadicus and pudendus; and from the coccygeal plexus is the n. caudalis majos. (AU)