The Anterior Limb, 207 



(h) The serratus anterior. Origin in two portions : 



Cervical portion : Transverse processes of the posterior five 



cervical vertebrae and the anterior two ribs. 



Thoracic portion: Third to ninth ribs by separate slips 



alternating with those of the external oblique. 



Common insertion: Medial surface of the vertebral border 



of the scapula. 



The transverse artery of the neck (a. transversa colli) lies on the 

 medial side of the cervical portion. 



2. Muscles arising from the axial skeleton and the pectoral 

 girdle and inserted on the humerus, for the most part at its proximal 

 extremity. 



Note the axillary lymph glands lying in the fat of the axillary 

 fossa. 



(a) The latissimus dorsi. Origin: Lumbodorsal fascia and 

 four posterior ribs. Insertion : Deltoid tuberosity. A 

 long flat triangular muscle, covering a considerable 

 portion of the lateral surface of the thorax; having 

 its dorsal angle covered by the thoracic portion of 

 the trapezius. Its insertion end passes to the medial side 

 of the humerus. 



(b) The pectoralis primus (p. tenuis). Origin: Manubrium 

 sterni. Insertion: Deltoid tuberosity. 



A branch of the thoracoacromial artery appears between this 

 muscle and the deltoideus. 



The muscle shoujd be raised from the surface and divided. 



(c) The pectoralis secundus (p. major). Origin: Entire 

 lateral portion of the sternum. Insertion: Anteromedial 

 surface of the humerus, beginning below the head, and 

 extending to the boundary between the middle and 

 distal thirds. The anterior fibres are covered by those 

 of (b). Some of the posterior fibres are inserted highest 

 on the humerus. 



By working backward from the clavicle the muscle can be detached 

 from those underneath and divided. 



