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670 
Original Article 

Biosci. J., Uberlândia, v. 33, n. 3, p. 670-674, May/June. 2017 

ORIGINS OF PLEXUS BRACHIAL IN Iguana iguana iguana 
 

ORIGENS DO PLEXO BRAQUIAL DA Iguana iguana iguana 
 

Rozana Cristina ARANTES
1
; Frederico Ozanam CARNEIRO E SILVA

2
;  

Ana Kelen Felipe LIMA
1
; Maria de Jesus Veloso SOARES

1
; Hassen JERBI

3
 

1. Course of Veterinary Medicine of Veterinarian Medical College of Tocantins Federal University of Campus Araguaína, TO, Brazil. 
rozanacristina.arantes@gmail.com; 2. Course of Veterinary Medicine of Veterinarian Medical College, Federal University of 

Uberlândia, Uberlândia, MG, Brazil. 3. Ecole Vétérinaire Sidi Thabet, Tunisie 

 
ASTRACT: This paper aims to describe the origin of the brachial plexus of 12 iguanas, male and female, which 

were donated already dead by the Wild Animal Screening Center and Independent Company of Highway and 
Environmental Police of the Araguaína, Tocantins State, to Veterinary Anatomy Laboratory of Federal University of 
Tocantins, Araguaína campus These animals were fixed by intramuscular injections of aqueous 10% formalin. It was made 
a parallel incision to dorsal midline from the skull to the caudal ribs. It was pulled all the epiaxial muscles eight ribs, the 
periosteum, exposing and individualizing the ventral rami of spinal nerves that make up the brachial plexus. The ventral 
rami of spinal nerves C6, C7, C8, T1 and T2 form the brachial plexus in 12 iguanas. In 41.6% of cases, the branches 
involved were C6, C7, C8 and T1; in 33.4%, the branches C6, C7, C8, T1 and T2; 16.6% the branches C7, C8, T1 and T2 
and in 8.4%, the branches C7, C8 and T1. The branches ventral C7, C8 and T1 formed three trunks and C6 and T2, when 
present, consisted of nervous fillet. There was variation in number of vertebrae in Iguana iguana iguana which caused 
oscillations in anastomoses, that constitute the nerves of brachial plexus. The axillary, subscapular, cutaneous, pectoral, 
coracobrachialis, radial, median, ulnar, thoracodorsal nerves are the main nerves that constitute the brachial plexus in 
iguanas. 

 
KEYWORDS: Forelimb. Iguana iguana iguana. Peripheral nervous system. Spinal nerve. 

 
 

INTRODUCTION 
 
There are 10,032 of reptiles species in 

world. In Brazil there were identified 760 species, 
belonging to 718 Squamata order, which includes 
snakes, lizards and amphisbaenians, 36 turtles and 
six alligators. Every year there are new species 
cataloged (SOUZA et al., 2013; BENÍCIO et al., 
2015). They inhabit the most different and diverse 
environments, especially warm areas (SOUZA et 
al., 2013). 

Iguana iguana iguana is a lizard of 
Iguanidae Family, and its body has spines along the 
back and tail looking like thorns, and also a large, 
round scaly under the eardrums and a gular fold 
well developed. The iguana displays varied colors, 
usually young ones have an vivid green color, while 
in adults, diversifies color and may have diffuse 
dark vertical stripes on the body and tail 
(ANDRADE, 2009). 

In vertebrates, the ventral rami of spinal 
nerves, located in regions of deployments of 
forelimbs and adjacencies constitutes the nerves that 
form the brachial plexus. The spinal nerves are 
named according to position that they occupy in the 
spine. The first cervical spinal nerve, C1, emerges 
lateral vertebral foramen atlas’, while the second 
spinal nerve, C2, emerges from the intervertebral 
foramen, located between the first cervical 

vertebrae, atlas, and the second cervical vertebrae, 
the axis (SCAVONE et al., 2008). 

In Agama agama and Chalarodon 
madagascariensis, brachial plexus originates in the 
ventral branches of spinal nerves 6, 7, 8, 9 and 10 
(RENOUS-LÉCURU, 1972). The brachial plexus, 
in birds, begins from the ventral rami of spinal 
nerves 12, 13, 14, 15 and 16 (BAUMEL, 1986). The 
brachial plexus, in Ornithorhynchus anatinus, 
corresponds to ventral branches of the cervical 
spinal nerves C4, C5, C6, C7, C8, thoracic spinal 
nerves T1 and T2, and in Tachyglossus aculeatus 
comprises the ventral branches of the spinal nerves 
C3, C4, C5, C6, C7, C8, T1 and T2 (KOIZUMI; 
SAKAI, 1997). 

The brachial plexus, in crocodiles, 
originates in the ventral rami of spinal nerves 7, 8, 
9, 10 and 11 (SUZUKI; HAYASHI, 2010). In 
Saimiri, the ventral rami of spinal nerves C4, C5, 
C6, C7, C8 and T1 equivalent to brachial plexus 
(ARAÚJO et al., 2012). The brachial plexus, in 
anteater, comprises the ventral branches of spinal 
nerves C5, C6, C7, C8 and T1 (CRUZ et al., 2012). 
In Hippopotamus amphibius, the brachial plexus 
originates from ventral rami of spinal nerves C5, 
C6, C7 and T1 (YOSHITOMI et al., 2012). In Falco 
columbarius, the brachial plexus corresponds to the 
ventral rami of spinal nerves C10, C11, C12, C13, 
T1 and T2 (CEVIK-DEMIRKAN, 2014). 

Received: 03/07/16 
Accepted: 20/11/16 



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Origins of plexus...        ARANTES, R. C. et al.  

Biosci. J., Uberlândia, v. 33, n. 3, p. 670-674, May/June. 2017 

The knowledge about Nervous System of 
reptiles is deficient, requiring research with 
emphasis on descriptive anatomy, histological and 
pathological these animals. This research aimed to 
describe the origins of iguana brachial plexus in 
order to be a compilation of Nervous System of 
species, with application in clinical and surgery 
practice. 

 
MATERIAL AND METHODS 

 
The Wild Animal Screening Center and 

Independent Company Highway and Environmental 
of Military Police donated 12 dead iguanas, eight 
males and four females, from different ages and 
length ranging from 0.6 to 1.25 meters, to 
Veterinary Anatomy Laboratory of Federal 
University of Tocantins, situated at Araguaína of 
Tocantins State.  

These animals were fixed in 10% formalin 
solution with intramuscular injections. Following 
that, a parallel incision to dorsal midline from skull 
to last rib was made, and all epiaxial muscles, eight 
ribs and periosteum were removed, exposing and 
individualizing the spinous processes for counting 
the vertebrae and identification of ventral rami of 
corresponding spinal nerves to the nerves that 
compose the brachial plexus. It was made a 
statistical analysis using the arithmetic average, 
schemed and photographed and the nomenclature is 
according to Baumel et al. (1993). The use of dead 
animals is consistent with Normative Instruction 

number 154/2007 of IBAMA and Law No. 11,794 / 
2008. 

  
RESULTS 

 
There are five iguanas with eight cervical 

vertebrae, 14 thoracic vertebrae, two sacral and a 
variable number of caudal vertebrae and seven 
iguanas with eight cervical vertebrae, 15 thoracic 
vertebrae, two sacral and various number of caudal 
vertebrae. The ventral rami of spinal nerves C6, C7, 
C8, T1 and T2 form the brachial plexus of 12 
iguanas and exhibit symmetry between the 
antimeres, consisting: in 41.6% of cases by ventral 
rami of spinal nerves C6, C7, C8 and T1; in 33.4% 
of cases by ventral rami of spinal nerves C6, C7, 
C8, T1 and T2; in 16.6% of cases by ventral rami of 
spinal nerves C7, C8, T1 and T2; and in 8.4% of 
cases by ventral rami of spinal nerves C7, C8 and 
T1. There are formed three trunks: cranial trunk: the 
ventral rami of spinal nerve C7; medium trunk: the 
ventral rami of spinal nerve C8 and the caudal 
trunk: the ventral rami of spinal nerve T1. And 
when presents, the ventral rami of spinal nerves C6 
and T2 consist of nervous fillet. 

There are several anastomoses between the 
ventral rami of cervical spinal nerves and ventral 
rami of spinal thoracic nerves in the formation of 
nerves that innervate the forelimbs, as shown in 
Table 1. In Figure 1, schematic representation of 
origin and distribution of brachial plexus nerves in 
one Iguana iguana iguana. 

 
Table 1. Origins of main nerves that compose the brachial plexus in Iguana iguana iguana.  

Nerve Origin 

Subscapular Ventral branch of spinal nerve C6 or C6 and C7 

Cutaneous Ventral branch of spinal nerve C6 and C7 or C8 

Pectoral Ventral branch of spinal nerve C7 or C8 and T1 

Coracobrachialis Ventral branch of spinal nerve C8, T1 and T2 

Axillary Ventral branch of spinal nerve C6 and C7 or C7 and C8 

Radial Ventral branch of spinal nerve C6, C7, C8, T1 and T2 or C8 or C8 and T1 

Median Ventral branch of spinal nerve C8 and T1 or C8, T1 and T2 

Ulnar Ventral branch of spinal nerve C6, C7, C8, T1 and T2 or C8, T1 and T2 or C8 and T1 

Thoracodorsal Ventral branch of spinal nerve C6 and C7 or C8 

 
 



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Origins of plexus...        ARANTES, R. C. et al.  

Biosci. J., Uberlândia, v. 33, n. 3, p. 670-674, May/June. 2017 

 
Figure 1. Schematic representation of brachial plexus of Iguana iguana iguana . C6 – sixth cervical vertebra. C7 

– seventh cervical vertebra. C8 – eighth cervical vertebra. T1 – first thoracic vertebra. T2 – second 
thoracic vertebra. 1 – thoracodorsal nerve. 2 – cutaneous nerve. 3 – subscapular nerve. 4 – 
coracobrachialis nerve. A – axillary nerve. M – median nerve. P – pectoral nerve. R – radial nerve. U 
– ulnar nerve. 

 
DISCUSSION 
 

The brachial plexus of these 12 iguanas 
comes from the ventral rami of last three cervical 
spinal nerves, C6, C7 and C8 and first two ventral 
rami of spinal thoracic nerves, T1 and T2. 

The data relating to set of nerves that make 
up the brachial plexus facilitate access to procedures 
such as anesthetic block the forelimb, achieving 
maximum effectiveness of anesthetic agent, 
decreased surgical time and anesthetic dose. The 
scarcity of reports about the origin of brachial 
plexus in wild animals especially lizards, possibility 
of comparison to representatives of Reptila class, 
however, is not always reliable because of large 
diversity of group. 

In origin of brachial plexus of iguana, 
compared to animals Reptila class, such as 
crocodiles and tortoises, there are contradictions 
since in crocodiles, the brachial plexus originates 
from ventral rami of spinal nerves 7, 8, 9, 10 and 11, 
which constitutes four nerve trunks and a nervous 
fillet (WYNEKEN, 2007; SUZUKI; HAYASHI, 
2010) while in red-legged tortoises, the brachial 
plexus originates from ventral rami of spinal nerves 
5, 6, 7, 8 and 9 (CARVALHO et al., 2011).It is 
expected the lack of consensus because despite 
belonging to the same class, have order, family and 
different genres, and these factors cause changes in 
the number of vertebrae and on-site implementation 
of thoracic member. 

By relating the origin of brachial plexus of 
iguana comparing with lizards from Squamata 
order, there is consonance with species Uracentron 
azureum, Lacerda lépida, Xenosaurus grandis, 
Chalcides acellatus, Gekko gecko, Uroplatus 
fimbriatus, Tarentola annularis, Agama agama, 
Chalarodon madagascariensis and Sphenodon 
punctatus. In these species, the origin of brachial 
plexus corresponds to ventral branches spinal nerves 
6, 7, 8, 9 and 10 (GREGORY; CAMP 1918; 
LÉCURU, 1968; RENOUS-LÉCURU, 1972). This 
correlation relates the presence of equal amounts of 
cervical vertebrae and consequently same site 
forelimb, however these species belong to different 
genera and families as a result of high variability, 
habitat interference, presence of food and predators. 

However, there is unconformity related to 
the origin of the brachial plexus of iguana with other 
lizard species such as Chamaeleon verrucosus, 
Chamaeleon parsoni, Brookesia spectrum and 
Lanthanotus borneensis. In these lizards three 
ventral branches of the spinal nerves are the source 
of brachial plexus, though there is variation in 
location of these branches, the Lanthanotus, plexus 
originates in ventral branches of spinal nerves 7, 8 
and 9 and Chamaeleon and Brookesia, brachial 
plexus corresponds to the ventral rami of spinal 
nerves 4, 5 and 6 (LÉCURU, 1968). This 
contradiction exemplifies the discrepancy in number 
of cervical vertebrae and the forelimb mounting 
location in axial skeleton. 



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Origins of plexus...        ARANTES, R. C. et al.  

Biosci. J., Uberlândia, v. 33, n. 3, p. 670-674, May/June. 2017 

In the current study, there is the presence of 
anastomoses in ventral rami of spinal nerves to form 
the axillary, subscapular, cutaneous, pectoral, 
coracobrachialis, radial, median, ulnar, 
thoracodorsal nerves, which are some of main 
nerves for thoracic limb. This characteristic is in 
agreement with findings of Renous-Lécuru (1972) 
who found variations in composition of nerves to 
the brachial plexus. This variability allows the 
survival of strains because conditions the 
maintenance of species to different individuals, 
making the changes and adaptations to habitat.  

CONCLUSIONS 
 

The ventral rami of spinal nerves C6, C7, 
C8, T1 and T2 form the brachial plexus in 12 
iguanas occurring several anastomoses and greater 
prevalence (41.6%) C6 to T1.  

The main nerves observed in Iguana iguana 
iguana are axillary, subscapular, cutaneous, 
pectoral, coracobrachialis, radial, median, ulnar, 
thoracodorsal nerves. 
 
 

 

 
RESUMO: Esse trabalho tem como objetivo descrever a origem do plexo braquial de 12 iguanas, machos e 

fêmeas, doados mortos pelo Centro de Triagem de Animais Silvestres e Companhia Independente de Polícia Rodoviária e 
Ambiental – Araguaína – Tocantins, ao Laboratório de Anatomia da Universidade Federal do Tocantins, campus de 
Araguaína. Fixou-se os animais com injeções intramusculares de solução aquosa de formalina a 10%. Realizou-se uma 
incisão paralela a linha mediana dorsal desde o crânio até a região caudal das costelas. Retirou toda a musculatura epiaxial, 
oito costelas, o periósteo, expondo e individualizando os ramos ventrais dos nervos espinhais que compõem o plexo 
braquial. Os ramos ventrais dos nervos espinhais C6, C7, C8, T1 e T2 formam o plexo braquial nas 12 iguanas. Em 41,6% 
dos casos, os ramos envolvidos foram C6, C7, C8 e T1; em 33,4%, os ramos C6, C7, C8, T1 e T2; em 16,6 % os ramos 
C7, C8, T1 e T2 e em 8,4%, os ramos C7, C8 e T1. Dos ramos ventrais C7, C8 e T1 formavam três troncos e C6 e T2, 
quando presentes, consistiam de filetes nervosos. Houve variação no número de vértebras na Iguana iguana iguana, que 
provocaram oscilações nas anastomoses que constituem os nervos do plexo braquial nas iguanas. Os nervos axillar, 
subscapular, cutâneo, peitoral, coracobraquial, radial, mediano, ulnar e toracodorsal são os principais nervos que 
constituem o plexo braquial nas iguanas.  

 
PALAVRAS CHAVE: Iguana iguana iguana. Membro torácico. Nervo espinhal. Sistema nervoso periférico. 

 
 
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