THORACIC VERTEBRA. 



I'S 



Superior articular process, 

 and facet 



Superior demi-facet for rib 



Articular facet, 

 on transverse 

 process 



Inferior demi-facet for rib 

 Inferior articular process 



Spinous process 



Sixth thoracic vertebra from the side. 



p7 0cesses^ on each side, one above and one below the lamina, forming true joints 



with the opposed processes of the neighboring vertebrae ; (7) a rib ox costal element, 



which in the thoracic region is a separate bone, in the cervical region is a part of the 



vertebra, and in the lumbar 



region mingles with the trans- F^g. 140. 



verse process. The costal ele- Pedicle 



ment is also represented in 



the sacrum. 



Thoracic Vertebrae. 



^A vertebra from the middle 



of the thoracic region is de- 

 scribed first as intermediate in 



several respects to the others. 

 The body is but a little 



broader transversely than 



from before backward. It is 



a little deeper behind than in 



front, thereby helping to form 



the curve of the spine. The 



upper and lower borders pro- 

 ject a little anteriorly. The 



upper and lower surfaces, as 



in all the vertebrae, are rough 



where the intervertebral disks 



join them. The posterior 



surface is concave from side 



to side, and presents in the 



middle one or two foramina 



for the escape of the veins. At the back of the side of the body there is half an 



articular facet both above and below, which, with the intervening disk, forms an oval, 



shallow socket for the head of the rib belonging to the lower vertebra. 



The spinal foramen, en- 

 closed by the arch, is circular. 



The pedicles, which are much 

 deeper than thick, arise from the 

 upper half of the body. The supe- 

 rior border rises gradually to the 

 articular process. The inferior bor- 

 der is concave, forming the top of 

 the ;?(?/<://, ^ which, when the succeed- 

 ing vertebra is in place, forms the 

 top of the intervertebral foramen^ 

 which is wholly behind the lower 

 half of the body. 



The laminae are broad, each 

 reaching to the level of those of the 

 next vertebra. 



The spinous process is long, 

 and points strongly downward, over- 

 lapping the one below. It has a 

 narrow under surface which is 

 grooved, and two lateral ones meet- 

 ing above in a ridge continued from 

 the laminae. This arrangement of 

 the laminae and spines completely 

 closes the cavity of the spinal canal. 



The spinous processes are slightly enlarged at the end for the supraspinous liga- 

 ment and muscles. 



The transverse processes are strong, having to support the ribs. They pro- 



^ Processus articularis. " Incisura vertebralis. '^ Foramen intervertebrale. 



Superior articu- 

 ar process 

 and facet 



Spinous process 



Sixth thoracic vertebra from behind. 



