38 



DISSECTION OF THE UPPER LIMB. 



relations ; 



Dissection 

 of supra- 

 scapular 

 vessels. 



Supra- 

 scapular 

 artery 



ends in 

 infraspina- 

 tus and 



subscapular 

 and supra- 

 spinous 

 offsets. 



Vein. 



Suprascapu- 

 lar nerve : 



branches, 

 muscular 



and articu- 

 lar. 



Posterior 

 scapular 

 artery. 



Dorsal sca- 

 pular artery 



The muscle is concealed by the trapezius and the acromion 

 process ; and it rests upon the scapula, the suprascapular vessels 

 and nerve, and the shoulder-joint. Its tendon joins that of the 

 infraspinatus at the attachment to the humerus. 



Action. It comes into use with the acroniial portion of the 

 deltoid in raising the limb and supporting the joint. 



Dissection (tig. 22, p. 52). The vessels and nerves on the 

 dorsum of the scapula can be traced by detaching from behind 

 forwards the supraspinatus and infraspinatus muscles, so as to leave 

 a thin layer of the fleshy fibres with the ramifying blood-vessels on 

 the surface of the bone. In the supraspinous fossa are the supra- 

 scapular vessels and nerve, which are to be followed beneath the 

 acromion to the infraspinous fossa ; and entering the infraspinous 

 fossa, beneath the teres minor muscle, is the dorsal branch of the 

 subscapular artery. The anastomosis between these vessels should 

 be pursued in the fleshy fibres and cleaned. 



The SUPRASCAPULAR ARTERY (a) is derived from the thyroid axis 

 of the subclavian trunk (p. 9). After a short course in the neck 

 it crosses over the suprascapular ligament, and passing beneath the 

 supraspinatus muscle, ends in the infraspinous fossa, where it gives 

 offsets to the infraspinatus muscle and the scapula, and anastomoses 

 with the dorsal branch of the subscapular artery and the posterior 

 scapular of the subclavian. 



Before entering the supraspinous fossa, it gives a small branch to 

 the ventral surface of the scapula ; and beneath the supraspinatus it 

 furnishes offsets to that muscle, the bone, and the shoulder-joint. 



The companion vein of the suprascapular artery joins the external 

 jugular vein. 



The SUPRASCAPULAR NERVE (*) is a branch of the brachial plexus 

 (5th and 6th cervical nerves ; fig. 8, sps., p. 26). At the upper 

 border of the scapula ; it enters the supraspinous fossa beneath the 

 suprascapular ligament. In the fossa it supplies two branches to 

 the supraspinatus ; and it is continued beneath a fibrous band to 

 the infraspinatus muscle, in which it ends. 



The nerve gives some articular filaments to the shoulder-joint, 

 and other offsets to the scapula. 



The POSTERIOR SCAPULAR ARTERY runs along the base of the 

 scapula beneath the rhomboid muscles, furnishing offsets to them 

 and to the surfaces of the bone. It has been more fully noticed 

 with the dissection of the back (p. 9). 



The DORSAL SCAPULAR ARTERY (6) is a branch of the subscapular 

 (p. 24), and, after giving off its infrascapular offset, turns round 

 the axillary border of the bone opposite the posterior of the two 

 spaces between the teres muscles. Entering the infraspinous fossa 

 beneath the teres minor, it supplies that muscle and the infraspi- 

 natus, and anastomoses with the suprascapular and posterior scapular 

 arteries. It sends a considerable branch downwards between the 

 teres muscles, towards the lower angle of the bone. 



