260 ANATOMY IN A NUTSHELL. 



peculiar. The peculiarity of the first dorsal is that it has one facet and a demi- 

 facet. The ninth dorsal has a demi-facet only. The tenth has but one facet 

 mi its body and one on the transverse process. The eleventh and twelfth have 

 each but one facet on the body, and none on the transverse process. The 

 twelfth resembles a lumbar vertebra in size and shape. The fifth lumbar is much 

 deeper in front than behind. Its spinous process is small, but its transverse 

 processes are large and thick and point slightly upward. 



The atlas has ten pairs of muscles attached to it. 

 I'm anterior arch. Longus Colli. 1 Ant. vertebral region. 



To posterior arch. Rectus capitis posticus minor. 2 Fifth layer of back. 



Rectus capitis anticus minor. 3 Ant. vertebral region. 

 Rectus capitis lateralis. 4 Ant. vertebral region. 

 Inferior oblique. 5 Fifth layer of back. 

 To transverse pro- Superior oblique. 6 Fifth layer of back, 

 cess. Splenius colli. 7 Third layer of back. 

 Levator anguli scapula?. 8 Second layer of back- 

 Anterior intertransversalis. 9 Fifth layer of back. 

 Posterior intertransversalis. 10 Fifth layer of back. 



The atlas has a small spinous process, large lateral masses, and no body. 

 The anterior arch forms one-fifth of the circumference, the posterior arch two- 

 fifths of the circumference, and the lateral masses one-fifth each. The attach- 

 ment of muscles is given above. There is a groove on the posterior surface of 

 the anterior arch for the articulation of the odontoid process of the axis. This 

 process is held in place by the transverse ligament which passes across it pos- 

 teriorly, being attached to the inner surface of the lateral masses. Where the 

 posterior arch joins the lateral masses there is a groove (sinus atlantis) for the 

 vertebral artery and suboccipital nerve (first spinal nerve), the nerve lying be- 

 neath the artery. The articulation of the atlas with the occiput is a diarthrosis 

 joint, subclass double condylar arthrosis, having all the movements of the ball- 

 and socket joint (enarthrosis) except axial rotation. (Plate XCV.) 



The blood supply of this joint is the vertebral artery and sometimes the 

 ascending pharyngeal artery. 



The nerve supply is the anterior division of the suboccipital (first cervical.) 



The ligaments are the anterior occipito-atlantal, posterior occipito-atlantal, 

 two capsular, two anterior oblique or lateral occipito-atlantal. (Plate CIX.) 



The anterior occipito-atlantal ligament is attached above to the anterior 

 margin of the foramen magnum, below to the upper margin of the anterior arch 

 of the atlas. The central part, which is a continuation of the anterior common 

 ligamenl of the vertebral column, is sometimes called the superficial part of 

 this ligament. The lateral portions, which are continuous with the capsular 

 ligament, form the deep part. In front of this ligament are the Recti capitis 

 antici minores muscles. H( hind is the central odontoid or suspensory ligament. 



