Comparison between cervical vertebrae of man and of the domestic animals

Abstract

Anatomy is the science that studies the form, architecture and structure of living beings, and the modality that explores the morphological differences between species is called comparative anatomy. Among the bone structures that make up the axial skeleton of individuals, the cervical vertebrae stand out, considered odd and irregular bones. Given the relevance of cervical vertebrae, the objective of the present study was to compare such bone elements in humans and domestic animals (dogs, horses and cattle) and, nevertheless, highlight the structural similarities in these different species in terms of quantities, functions and formats in resulting from bone accidents. For this, skeletons and individual anatomical pieces from the Human and Veterinary Anatomy Laboratory of the University of Franca (UNIFRAN - Franca, SP) were used, as well as anatomy books renowned in this area of ​​specialty and scientific articles. The results were presented in a descriptive way. As for quantity, humans have seven cervical vertebrae, just like dogs, horses and cattle. In all species, the cervical vertebrae support the neck, providing movement of the head and protection of the cervical spinal cord. Regarding shape, the first (atlas) and second (axis) cervical vertebrae are atypical in all species. The atlas has an arched body, containing the dorsal and ventral tubercle; furthermore, the transverse process is modified (wing of the atlas) with the alar foramen and lateral vertebral foramen. The caudal articular surface of the atlas (fovea dentis) articulates with the odontoid process of the axis. Cattle do not have a transverse foramen and, in no species, does the spinous process appear in the atlas. The axis had a rod-shaped odontoid process in dogs, concave in cattle and pointed in other species, in addition to an elongated spinous process. The other cervical vertebrae are typical, composed of a vertebral body (with head of the vertebra and vertebral fossa), vertebral arch (participates in the formation of the vertebral foramen), vertebral foramen (houses the spinal cord) and spinous processes (poorly developed), transverse (well developed, containing the transverse foramen) and cranial and caudal articular (flat surfaces). In all species, the seventh cervical vertebra is modified, presenting a long spinous process and reduction or absence of the transverse foramen; furthermore, in horses, the spinous process was detected only in this vertebra. In humans, dogs, horses and cattle, the seventh cervical vertebra has a pair of caudal costal facets for articulation with the first pair of ribs. Given the results obtained, it is accepted that the anatomical morphological similarities and differences between the cervical vertebrae may be related to the functional, evolutionary and postural aspects of the different species studied.