50 



SPECIAL ANATOMY OF THE SKELETON 



two divisions being often of unequal size. They increase in length from the fourth 

 to the seventh vertebra. 



Articular Processes. The articular processes are flat, oblique, and of an oval 

 form; the superior are directed backward and upward, the inferior forward and 

 downward. 



Transverse Processes. The transverse processes are short, directed down- 

 ward, outward, and forward, bifid at their extremity, and marked by a groove 

 along the upper surface, which runs downward and outward from the superior 

 intervertebral notch and serves for the transmission of one of the cervical nerves. 

 They are situated in front of the articular processes and on the outer side of the 

 pedicles. The transverse processes are pierced at their bases by a foramen, 

 for the transmission of the vertebral artery, vein, and a plexus of sympathetic- 

 nerves. This foramen is known as the transverse foramen, the costotransverse 

 foramen, and the vertebrarterial foramen (foramen transversarium). Each process 

 is formed by two roots the anterior root, sometimes called the costal process, 

 arising from the side of the body, and the homologue of the rib in the thoracic- 

 region of the column ; the posterior root springs from the junction of the pedicle 

 with the lamina, and corresponds to the transverse process in the thoracic region. 



Anterior tubercle of trans- 

 verse process, 



Costotransverse foramen for 



vertebral artery and vein and 



sympathetic plexus. 



Posterior tubercle, of 

 transverse process. 



I Spinousi 

 I process. 



FIG. 15. Cervical vertebra. 



Transverse process. 



^-Superior articular 



process. 

 Inferior articular process. 



It is by the junction of the two that the foramen for the vertebral vessels is formed. 

 The extremity of each of these roots form the anterior and posterior tubercles 

 of the transverse processes. 1 



The peculiar vertebra? in the cervical regions are the first, or atlas; the second, 

 or axis; and the seventh, or vertebra prominens. The great modifications in the 

 form of the atlas and axis are designed to admit of the nodding and rotatory 

 movements of the head. 



Atlas. The atlas (Fig. 16) is so named because it supports the globe of the 

 head. The chief peculiarities of this bone are that it has neither body nor spinous 

 process. The body is detached from the rest of the bone, and forms the odontoid 

 process of the second vertebra; while the parts corresponding to the pedicles 

 join in front to form the anterior arch. The atlas is ring-like, and consists of 

 an anterior arch, a posterior arch, and two lateral masses. The anterior arch 

 (arcus anterior} forms about one-fifth of the ring; its anterior surface is convex, 

 and presents about its centre a tubercle (tuberculum anterius), for the attachment 

 of the Longus colli muscle; posteriorly it is concave, and marked by a smooth, 



1 The anterior tubercle of the transverse process of the sixth cervical vertebra is of large size, and is some- 

 times known as "Chassaignac's," or the "carotid tubercle" (tuberculum caroticum). It is in close relation with 

 the carotid artery, which lies in front and a little external to it; so that, as was first pointed out by Chassaignac, 

 the vessel can with ease be compressed against it. 



