^ 



32 THE SKELETON 



Articular processes. — Both the superior and inferior articular processes are 

 situated at the junction of the root with the lamina and they form the upper and 

 lower extremities of a small column of bone. The articular surfaces are oblique 

 and nearly fiat, the superior looking backward and upward, and the inferior 

 forward and downward. 



The transverse process presents near its base a round costo-transverse foramen 

 [foramen transversarium] for the transmission of the vertebral artery, vein, and a 

 plexus of sympathetic nerves. Moreover, each process is deeply grooved above 

 for a spinal nerve, and is bifid at its free extremity, terminating in two tubercles — 

 anterior and posterior. The costo-transverse foramen is very characteristic of a 

 cervical vertebra. It is bounded medially by the pedicle, posteriorly by the 

 transverse process (which corresponds to the transverse process of a thoracic 

 vertebra), anteriorly by the costal process (which corresponds to the rib in the 

 thoracic region), and laterally by the costo-transverse lamella. The latter is a 

 bar of bone joining the two processes and directed obliquely upward and forward 

 in the upper vertebrae and horizontally in the lower. The vertebral foramen is 

 triangular with rounded angles, and is larger than in the thoracic or lumbra 

 vertebrae. 



Fig. 35. — A Cervical Vertebra. 



Costal process 



Costo-transverse foramen - ^' \^_ J ^^^^i^=^^Mi J ^^Pedicle (root of arch) 

 Transverse process 



Superior articular process 



Inferior articular process 

 Lamina 



Spinous process 



Peculiar cervical vertebrae. — The various cervical vertebra? possess distinguishing features, 

 though, with the exception of the first, second, and seventh, which are so different as to necessi- 

 tate separate descriptions, these are largely confined to the direction of the costo-transverse 

 lamella, and the size and level of the anterior and posterior tubercles. In the third the anterior 

 tubercle is higher than the posterior and the costo-transverse lamella is oblique; in the fourth the 

 anterior tubercle is elongated vertically, so that its lower end is nearly on a level with the 

 posterior, though the lamella still remains oblique. In the fifth and sixth they are nearly on 

 the same level, but in the latter the anterior tubercle is markedly developed to form the carotid 

 tubercle. 



The Atlas or First Cervical Vertebra 



This verte])ra (fig. 36) is remarkable in that it has neither body nor spinous 

 process. It has the form of an irregular ring, and consists of two thick portions, 

 the lateral masses, united in front and behind by bony arches. The anterior 

 arch joins the lateral masses in front and constitutes about one-fifth of the entire 

 circumference of the ring. On its anterior surface it presents a tubercle for the 

 attachment of the longus colli muscle and the anterior longitudinal ligament, 

 and on its posterior surface a circular facet [fovea dentis] for articulation with 

 the odontoid process [dens] of the axis. The upper and lower borders serve for 

 the attachment of ligaments uniting the atlas to the occipital bone and axis 

 respectively. 



The lateral masses are thick and strong, supporting the articular processes above and below 

 and extending laterally into the transverse processes. The sui)crior articular surfaces are 

 elongated, (lr'e[)ly concave, and converge in front. Directed upward and medially they receive 

 the condyles of the occii)ital l)oii(!, and occasionally each prcscsnts two oval facets united by an 

 isthmu.s. The inferior articular surfaces are circular and almost flat; they are directed down- 

 ward and meilially and articulate with the axis. The articular processes, like the superior 

 artif;ular processes of tlu; axis, (hlfer from those of other vertebra) in being situated in front of 

 the i)laces of exit of the spinal nerves. 



Uetwcen the upper and lower articular surfat^es on the inside of the ring are two smooth 

 rounded tubercles, one on each side, to which the transverse ligament is attached. This liga- 



