The first cervical vertebra (Atlas; C1) differs considerably from other cervical vertebrae to allow free movement of the head:
The atlas posses no body and is composed by two lateral masses joined by dorsal and ventral arches, constituting a bony ring for the beginning of the vertebral canal. The lateral masses present two cranial articular fovea for articulation with the paired occipital condyles and two caudal articular fovea for articulation with articular surfaces of axis.
The transverse processes expand to project laterally of each masse, forming shelf-like processes termed the wing of atlas. Each wing is hollowed to form the atlantic fossa on their flat ventral surface. The base (cranial) of each wing is perforated by the alar foramen (absent in carnivores, replaced by the alar notch) for passage of vertebral artery.
Reference :Text by Antoine Micheau, MD - IMAIOS Veterinary Anatomy of Dustrated Veterinary Anatomical Nomenclature - 3rd edittion - Gheorghe M. Constantinescu, Oskar Schaller - Enke
Comments