Vertebral Column 



Posterior arch shows on its upper surface a broad groove for the vertebral artery 

 and suboccipital nerve, just behind the articular mass and leading from the foramen 

 in the transverse process ; behind the groove, a ridge for the posterior occipito-atlan 

 toid ligament. Transverse process projects from the lateral mass and has a large 

 foramen : its front bar may show a small terminal tubercle, but the end of the 

 process corresponds with the posterior tubercles of the lower vertebrae. The large hole 

 enclosed by the arches has a front part into which the odontoid process projects from 

 below, and a larger posterior part which is the proper spinal foramen. Lower articular 

 processes, being broader than the upper ones, encroach somewhat on the front part 

 of the space by their inner margins, and on these are vascular foramina and tuber- 

 culated roughnesses for the attachment of the transverse ligament that passes behind 

 the odontoid process, and of the accessory alto-axoid ligament. 



AXIS (Fig. 12). 



Remarkable owing to the presence of the odontoid process, or dens, which projects 

 upwards : this is really the centrum of the Atlas, separated from that bone and fixed to 

 the upper surface of body of Axis, and it articulates by its front surface with the facet 

 on the anterior arch of the Atlas. Dens has an extremity roughened by attachment 

 of occipito-odontoid ligaments, and a slight constriction behind for the transverse 

 ligament, a bursa intervening ; the true body of the Axis is below the base of the process. 

 Upper articular surfaces look up- 

 wards and outwards and are placed 

 a little distance outside the base of 

 odontoid, but the lower processes 

 are further back, corresponding with 

 the position of the process in the 

 lower cervical segments : the second 

 nerve makes its exit behind the upper 

 process, and the third in front of the 

 lower, as in the vertebrae below the 

 Axis. 



Transverse process short, ending 

 in a single (posterior) tubercle : arte- 

 rial foramen is a canal which, pass- 

 ing upwards, reaches under part of 

 upper articular mass and turns out- 

 wards sharply. Internal to the 

 arterial canal a thick column of 

 bone transmits the weight of the 

 Atlas and head from the upper ar- 

 ticular process to the body. The laminae are strong, and a broad, strong, elongated 

 bifid spine is continued back from them. 



The pedicles can be seen from below, and recognised as being in their usual positions, 

 but their upper surfaces are hidden by the upper articular processes 



The nodding movements of the skull (flexion and extension) take place between 

 the Atlas and Occipital, while rotation is carried out between the Atlas and Axis. 

 To permit and control these movements there are, in addition to the capsules of the 

 articular processes, two important systems of ligaments. The first is a strong band 

 thrown across from one lateral mass of the Atlas to the other, behind the odontoid 



MCV 



FIG. 12 The second cervical vertebra shown resting on the 

 third vertebra ; seen from the right and above. 

 /. facet on the front of odontoid process. Observe 

 that only the lower articular process is in line with 

 those of the vertebrae below. 



