90 



OSTEOLOGY. 



THE TRUE OR MOVABLE VERTEBRAE. 



Vertebras Cervicales. 



The cervical vertebrae, seven in number, can be readily distinguished from 

 all the other vertebrae by the fact that their transverse processes are pierced by 

 a foramen. The highest two, and the lowest, require special description; the 

 remaining four conform to a common type. 



Their bodies, the smallest of all the true vertebrse, are oblong in shape, the 

 transverse width being much longer than the antero- posterior diameter. The 

 superior surface, which slopes from behind forwards and downwards, is concave 

 from side to side, owing to the marked projection of its lateral margins. Its 

 anterior lip is rounded off, whilst its posterior edge is sharply defined. The inferior 

 surface, which is more or less saddle-shaped, is directed downwards and backwards. 

 It is convex from side to side, and concave from before backwards, with a slight 

 rounding off of the projecting anterior lip. The vertical diameter of the body is 

 small in proportion to its width. The anterior surface is flat in the middle line, 

 but furrowed laterally. The posterior surface, which is rough and pierced by many 

 small foramina, is flat from side to side and above downwards ; it forms part of 



Bifid spine 



Superior articular process Superior notch 



Foramen transversarium 



jratnen transversarium 

 Anterior tubercle A 



Spinous process 



Inferior notch 

 Inferior articular process 



B 



FIG. 107. FOURTH CERVICAL VERTEBRA, (A) from above, and (B) from the right side. 



the anterior wall of the vertebral foramen. The lateral aspect of each body, par- 

 ticularly in its upper part, is fused with a root of the arch and with the costal 

 part of a transverse process, and forms the medial wall of a foramen transversarium. 



The roots of the vertebral arches, which spring from the posterior half of the 

 lateral aspects of the body, about equidistant from their superior and inferior 

 margins, are directed horizontally backwards and laterally. The superior and 

 inferior notches are nearly equal in depth. The laminae are long, and about as 

 high as the bodies of the bone. The vertebral canal is larger than in the thoracic 

 and lumbar regions ; its shape is triangular, or more nearly semilunar. 



The transverse processes, so called, are pierced by the foramen transversarium 

 (vertebrarterial or transverse foramen). They consist of two parts the part behind 

 the foramen, which springs from the vertebral arch and is the true transverse 

 process, and the part in front, which is homologous with a rib in the thoracic 

 portion of the column. These two processes are united laterally by a bridge of bone, 

 which thus converts the interval between them into a foramen, and they terminate, 

 beyond the bridge, in two tubercles, known as the anterior and posterior tubercles. 



The general direction of the transverse processes is laterally, slightly forwards, 

 and a little downwards, the anterior tubercles lying medial to the posterior. The 

 two tubercles are separated above by a groove directed laterally, downwards, and 

 forwards ; along this the spinal nerve trunk passes. The foramen transversarium 

 is often subdivided by a spicule of bone. In the recent condition and in the cases 

 of the upper six vertebrse it is traversed by the vertebral artery and vein. 



The spinous processes, which are directed backwards, are short, compressed 

 vertically, and bifid. The articular processes are supported on cylindrical masses of 



