HEAD AND ANTERIOR CERVICAL STRUCTURES. 21 



Sterno-cleido-mastoid, 473-4-5. (467-8) Also, 1126-7. ( II0 3) 



Origin; sternal head, clavicular head. Insertion. Structure. Nerve-supply. 

 Action. Relations. Variations. 



The sterno-cleido-mastoid divides the side of the neck into an anterior and a posterior 

 triangular space. The boundaries of the posterior space are formed by the clavicle 

 below, the sterno-cleido-mastoid in front, the trapezius behind, and the occiput above. 

 The posterior belly of the omo-hyoid crosses the space about an inch above the clavicle, 

 and divides it into an upper or occipital, and a lower or subclavian triangle. The floor 

 of the space is formed from above downward by the splenius, levator anguli scapula, 

 scalenus medius, and posticus. 



Posterior Triangle, 1129. (1106) 



Carefully remove the fascia and dissect out the connective tissue and fat, exposing the structures in the 

 posterior triangular space. 



Omo-hyoid, 476 ; Fig. 314. (469) 



(Origin. Insertion. Structure. Relations.) 

 Spinal accessory nerve, 1130. (1106-7) 

 Branches to the trapezius, 831. (812) 

 Nerves to the levator anguli scapulse, 831. (812) 

 Third portion of the subclavian artery, 538-9. (529-30) 

 Relations : In front. 



Behind. 



Below. 



Above. 



The outer portion of the transverse cervical and suprascapular arteries will be exposed, the origin of the 

 vessels will be shown later. 



Transverse cervical or transversalis colli artery, 546-7. (537) 

 Suprascapular or transversalis humeri, 546. (536) 



Branches of the suprascapular : 



(i), (2), (3), (4). 

 Veins : 



External jugular vein, 1130. (1106) 



Suprascapular veins, 654. (641) 



Transverse cervical veins, 654. (642) 



Subclavian vein, 682-3. (668) 



Tributaries. 

 Anterior Triangular Space. 



The muscles forming the boundaries of the smaller triangles should first be exposed. Remove 

 the fascia forming the sheaths of the muscles and dissect out the fat and connective tissue. The small 

 nerves, the arterial branches, and the venous tributaries must all be carefully preserved. Beginning at 

 the symphysis, expose the anterior belly of the digastric; then the posterior belly anterior to the border 

 of the sterno-mastoid, removing the portion of the parotid gland superficial to it. The process of fascia 

 binding the tendon to the hyoid bone should be preserved. In exposing the omo-hyoid avoid injury to 

 the branches of the ansa hypoglossi which pass to it. 



Digastric, 478-9 ; Fig. 314. (471-2) 



Origin : anterior belly (posterior belly). Insertion. Structure. 



Nerve-supply. Action. Relations. Variations. 

 Stylo-hyoid, 479 ; Fig. 314. (472) 



Origin. Insertion. Structure. Nerve-supply. Action. Relations. Variations. 

 Omo-hyoid, 476 ; Fig. 314. (469-70) 



(Origin.) Insertion. Structure. Nerve-supply. Action. Relations. Variations. 

 Anterior triangle, 1127-8-9. (1104-5-6) 



Subdivided into three triangles: 



Submaxillary or supra-hyoid triangle. 

 Superior carotid triangle. 

 Inferior carotid or tracheal triangle. 



Before continuing the dissection the student requires some preliminary knowledge of the 

 structures in the anterior triangle, their position, relations, etc. The following general 

 description {modified by Cunningham) should be carefully studied. 



