ABSTRACT
Oxygenated blood is required for the adequate metabolic activity of the brain. This is supplied by the circle of Willis (CoW) and the vertebrobasilar and carotid systems. The CoW ensures blood flow in case of arterial stenosis or occlusion. Different animal models have been explored for the CoW morphological and functional study. This work aims to characterize the vascular architecture of the CoW of the plains vizcacha, Lagostomus maximus (Suborder: Hystricomorpha), and to compare it with evolutionarily related species of Caviomorpha and Muroidea. The blood supply in adult plains vizcachas was studied using latex cerebrovascular casts and angiography. A caudo-rostral flow direction was determined, beginning in the spinal and vertebral arteries and converging in the basilar artery which bifurcates in the carotid-basilar communication in the caudal communicating arteries. In the first third of its course, the caudal cerebral arteries project laterally, and the middle and rostral cerebral arteries bifurcate from their rostral terminal segment, supplying the temporo-parietal and frontal cortex. The CoW architecture is mainly conserved between rodent species. Likewise, the small neurovascular variations observed could be considered phylogenetic morphological variations more than evolutionary adaptations. The absence of the rostral communicating artery that generates the rostral open architecture of the CoW in the vizcacha as in the other analyzed species, supports the need for a revision of the CoW classical function as a security system. Finally, this work supports the importance of expanding our understanding of brain anatomy among species, which may contribute to a better understanding of functional neuroanatomy.
Subject(s)
Brain , Hemodynamics , Animals , Phylogeny , Circle of Willis , South America , Cerebrovascular CirculationABSTRACT
El músculo romboides (m. rhomboideus) forma parte de la sinsarcosis que une la cintura del miembro torácico con el esqueleto axil en los mamíferos domésticos. En estas especies, está integrado por los músculos romboides cervical (m. rhomboideus cervicis) y romboides torácico (m. rhomboideus thoracis), siendo imposible establecer el límite entre ellos, a diferencia de lo que sucede en el Hombre. Los carnívoros en general, el cerdo y el conejo presentan, además de las partes mencionadas, el músculo romboides de la cabeza (m. rhomboideus capitis). En la llama, la porción cefálica está ausente y la cervical pobremente desarrollada. Los autores proponen sumar a las porciones cervical y torácica del músculo romboides de este camélido sudamericano, al músculo romboides supraescapular (m. rhomboideus suprsacapularis), descrito por Lesbre (1903), en el camello y el dromedario. En este trabajo se establecen las inserciones, dimensiones e inervación del músculo romboides supraescapular de la llama, elementos que permiten definirlo como otra porción del complejo muscular romboideo en dicha especie. Además, se postula su acción como elevador de la escápula, dirigiéndola craneal y dorsalmente.
The rhomboideus muscle of the domestic mammals is part of the muscular set that joins the scapular waist to the axial skeleton. In these animals, the forenamed muscle has a cervical portion (m. rhomboideus cervicicis), and a thoracic portion (m. rhomboideus thoracis). Unlike in the man, these parts cannot be separated. In addition, carnivores, pigs and rabbits also have a cephalic portion (m. rhomboideus capitis). In the llamas, the cephalic portion is absent, and the cervical part is poorly developed. The authors propose to add a suprascapular portion (m. rhomboideus suparsacapularis), first described by Lesbre, 1903 in camels, to the Rhomboideus muscular complex of the llama. In this study, the authors describe the length, insertions, and inervation of the Rhomboideus Suprascapular muscle of the llama in order to define it as another portion of the Rhomboideus muscular complex. Moreover, the forenamed muscle is proposed as a scapular elevator.
