444 THE MUSCULAE SYSTEM. 



Nerve-Supply. Posterior rami of the spinal nerves. 



Actions. These muscles are concerned in extension, lateral movement and rotation of the 

 spine. 



Fourth Group. 



This group includes several sets of small muscles, which are vertebro-cranial or 

 intervertebral in their attachments. 



The muscles bounding the suboccipital triangle are four in number obliqui 

 capitis, inferior and superior, and recti capitis posteriores, major and minor. 



These muscles are concealed by the semispinalis capitis and splenius capitis ; 

 ihey enclose a triangular space (the suboccipital triangle) in which the vertebral 



ry, the posterior ramus of the suboccipital nerve, and the posterior arch of the 

 atlas are contained. 



Semispinalis capitis (insertion) 



Rectus capitis posterior minor \^^~ ~-~-^Trapezius (origin) 



(insertion) 



Rectus capitis posterior major 

 (insertion) 



Sterno-cleido-mastoid 

 ^(insertion) 



Splenius capitis 

 (insertion) 



Obliquus capitis superior 

 (insertion) 



Rectus capitis lateralis (insertion) 



Rectus capitis anterior (insertion) 



-Superior constrictor of pharynx (insertion) 

 Longus capitis (insertion) 



FIG. 396. MUSCLE- ATTACHMENTS TO THE OCCIPITAL BONE. 



The obliquus capitis inferior arises from the spine of the epistropheus, and 

 is inserted into the transverse process of the atlas. 



Nerve- Supply. Posterior ramus of the first cervical (suboccipital) nerve. 

 Actions. Extension, lateral flexion and rotation of the atlas in the axis. 



M. Obliquus Capitis Superior. The obliquus capitis superior arises from 

 the transverse process of the atlas, and is inserted into the occipital bone deep 

 and lateral to the semispinalis capitis and above the inferior nuchal line (Fig. 396). 



Nerve -Supply. Posterior ramus of the first cervical (suboccipital) nerve. 

 Actions. Elevation, lateral movement and rotation of the head on the atlas. 



M. Rectus Capitis Posterior Major. The rectus capitis posterior major 



arises from the spine of the second cervical vertebra, and is inserted into the 

 occipital bone deep to the obliquus capitis superior and semispinalis capitis and 

 below the inferior nuchal line (Fig. 396). 



Nerve-Supply. Posterior ramus of the first cervical (suboccipital) nerve. 

 Actions. Elevation, lateral movement and rotation of the head. 



M. Rectus Capitis Posterior Minor. The rectus capitis posterior minor 

 arises deep to the preceding muscle from the posterior tubercle of the atlas, and is 



