598 



DISSECTION OF THE NECK. 



Cords of the 



brachial 



plexus. 



Branches 



in the neck 

 are : 



Nerves of 

 scaleni and 

 longns colli 



Nerve of 

 rhomboids. 



Nerve of 

 serratus. 



Nerve of 

 subclavius. 



Suprascapu- 

 lar nerve. 



Offset to the 

 phrenic. 



Cervical 

 plexus. 



Arrange- 

 ment of the 

 nerves. 



Its offsets 

 are super- 

 ficial ; 



to form the outer cord of the plexus : the posterior divisions of the 

 three trunks by their union give rise to the posterior cord ; while 

 the large anterior division of the lower trunk is continued as the 

 inner cord. The three cords accompany the subclavian artery, lying 

 to its acromial side, and are continued to the axilla where the 

 nerves of the limb arise. 



Branches. The branches of the plexus may be classed into those 

 above the clavicle, and those below that bone. Those of the 

 upper set end mostly in muscles of the lower part of the neck and 

 of the scapula ; while the lower set consists of the branches to the 

 upper limb, with which they have been described. 



BRANCHES ABOVE THE CLAVICLE. Branches for the scaleni and 

 longus colli muscles. These small twigs arise from the nerves close 

 to the intervertebral foramina, and are seen when the anterior 

 scalenus is divided. 



The branch for the rhomboid muscles (fig. 216, rh) springs from 

 the fifth nerve, and perforates the fibres of the scalenus medius ; 

 it is directed backwards beneath the levator anguli scapulae to its 

 destination. Branches are given usually from this nerve to the 

 levator anguli scapulae. 



The nerve of the serratus (pt), the posterior, or long, thoracic nerve, 

 arises from the fifth, sixth, and generally also the seventh, nerves near 

 the intervertebral foramina. Piercing the fibres of the scalenus 

 medius lower than the preceding branch, the nerve is continued 

 downwards behind the brachial plexus, and enters the serratus 

 magnus muscle on its axillary surface. 



The nerve of the subclavius muscle (sc) is a slender branch, which 

 arises from the trunk formed by the fifth and sixth nerves, and is 

 directed downwards over the subclavian artery to the deep surface 

 of the muscle ; it often sends a twig to the phrenic nerve at the 

 lower part of the neck. 



The suprascapular nerve (sps) is the largest of these branches, and 

 arises from the trunk of the plexus formed by the fifth and sixth 

 nerves. It is destined for the muscles on the dorsum of the 

 scapula, and has been dissected with the arm. 



Occasionally an offset from the fifth cervical trunk joins the 

 phrenic nerve on the anterior scalenus muscle. 



The CERVICAL PLEXUS, formed by the upper four cervical nerves, 

 lies beneath the upper half of the sterno-mastoid muscle, and on the 

 middle scalenus and the levator anguli scapulae. Each nerve 

 entering the plexus, except the first, divides into an ascending and 

 a descending branch, and these unite with corresponding parts of 

 the adjacent nerves, so as to give rise to a series of arches. From 

 these arches or loops the different branches arise : 



The brandies are superficial and deep. Those of the superficial 

 set are again subdivided into ascending and descending, and have 

 been described with the posterior triangular space of the neck 

 (}>. 578). The ascending branches may be now seen to spring from 

 the union of the second and third nerves ; and the descending, to 

 take origin from the loop between the third and fourth nerves. 



