THE CERVICAL VERTEBRM 31 



laminae in the thoracic region are imbricated or sloped, one pair over the other, 

 somewhat like tiles on a roof. 



The spinous process [processus spinosus], long and three-sided, projects back- 

 ward and downward from the centre of the arch and terminates in a slight tubercle. 

 It gives attachment by its prominent borders to the interspinous ligaments and by 

 its free extremity to the supraspinous ligament. It serves mainly as a process for 

 muscular attachment. 



The transverse processes [processus transversus] are two in number and extend 

 laterally from the arch at the junction of the pedicles and laminae. They are long, 

 thick, backwardly directed columns of bone terminating in a clubbed extremity, 

 on each of which is a costal pit for articulation with the tubercle of a rib. The 

 transverse processes, in addition to supporting the ribs, afford powerful leverage 

 to muscles. 



TJig_grticular processes, two superior and two inferior, project upward and 

 downward opposite fKe attachments of the transverse processes. The superior 

 are flat and bear facets or surfaces [facies articulares superiores] which are dir ected 



Fig. 34. — A Thoracic Vertebra. (From above.) 

 ^^^^^^ mi Spinous process 



Costal pit for tubercle of rib 



( 



Pedicle (root of arch) 

 Costal pit for head of rib 



Transverse process 



upward, backward, and laterally, and are situated a little in advance of the inferior, 

 the facets of which [facies articulares inferiores] are oval, concave, and directed 

 downward, forward, and medially. 



The vertebral foramen is bounded anteriorly by the body, posteriorly and on 

 each side by the arch. It is nearly circular, and is smaller than in the cervical or 

 the lumbar region. When the vertebrae are articulated, the series of rings con- 

 stitute the spinal or vertebral canal [canalis vertebralis], in which is lodged the 

 spinal cord. 



THE CERVICAL VERTEBRAE 



A typical cervical vertebra (from the third to the sixth inclusive) presents the 

 following characteristics (fig. 35) : — The body is smaller than in other regions of 

 the column and is of oval shape with the long axis transverse. The lateral mar- 

 gins of the upper surface are raised into prominent lips, so that the surface is 

 concave from side to side; it is also sloped downward in front. The inferior sur- 

 face, on the contrary, projects downward in front and is rounded off at the sides 

 to receive the corresponding lips of the adjacent vertebra. It is concave antero- 

 posteriorly and convex in an opposite direction. 



The roots (pedicles) are directed laterally and backward and spring from the 

 body about midway between the upper and lower borders. The superior and 

 inferior notches are nearly equal in depth, but the inferior are usually somewhat 

 deeper. The laminae are long, narrow, and slender. The spinous process is 

 short and bifid at the free extremity. 



