ANATOMY IN A NUTSHELL. 65 



arteries. There is often an accessory external mammary which is behind the 

 main branch. 



The anterior circumflex arises from the outer side of the axillary artery, 

 passing between the Coraco-brachialis and the short head of the Biceps around 

 the anatomical neck of the humerus to the under surf ace of the Deltoid, which 

 it supplies. A branch from this artery passes up the bicipital groove, with the 

 longhead of the Biceps, to supply the shoulder-joint;, [ts anastomoses with the 

 posterior circumflex and acromial thoracic. An occasional cut mucous branch 

 is often given to the floor of the axilla. 



The posterior circumflex comes from the posterior part of the artery, below 

 the subscapular. It passes through the quadrilateral space which is bounded 

 above by the Teres minor, below by the Teres major, on the inner side by the 

 long head of the Triceps and on the other side by the humerus; its veins and 

 the circumflex nerve go with it. It anastomoses with the anterior circumflex, 

 subscapular, suprascapular, acromial thoracic, and a branch from the superior 

 profunda. This artery maybe a branch from the brachial, superior profunda, 

 or may come from a common trunk with the subscapular. It goes to the Del- 

 toid, long head of the Triceps, Teres minor, shoulder-joint and head of the 

 humerus. 



The subscapular artery runs along the lower border of the Subscapularis 

 muscle with the subscapular nerve to the inferior angle of the scapula, where it 

 anastomoses with the posterior scapular and a terminal branch of the trans- 

 versalis colli; it also anatomoses with the intercostal and long thoracic arter- 

 ies. It gives branches to the glands and areolar tissue of the axilla, to the 

 Teres major, Latissimus dorsi. Subscapular which passes through the triangu- 

 lar space bounded above and internally by the Subscapularis, below by the 

 Teres major, and externally by the long head of the Triceps. It anastomoses 

 with the suprascapular and posterior scapular arteries. It gives branches to 

 the Subscapularis and Infraspinatus muscles. 



Relations. — First Portion of Axillary Artery. 



In Front. — (1) Pectoralis major, (2) Costo-coracoid membrane, (3) Ex- 

 ternal anterior thoracic nerve, (4) Acromio-thoracic vein, (5) Cephalic vein. 



Behind. — (1) First intercostal space, (2) First intercostal muscle, (3) 

 Second and third serrations of Serratus magnus. (4) Posterior thoracic nerve, 

 and (5) Internal anterior thoracic nerve. 



Outer Side. — Brachial plexus. 



[nnee Side. — Axillary vein. 



Second Portion of Axillary Artery. 



Ix Front. — (1) Pectoralis major. (2) Pectoralis minor. 



BEHIND. — (1) Subscapularis, (2) Posterior cord of plexus. 



Outer Side. Outer cord of plexus. 



Ixwkk Side.— (1) Axillary vein, (2) Inner cord of plexus, and (3) Inter- 

 nal anterior thoracic nerve. 



Third Portion of Axillary Artery. 



Ix Front. — (1) Integument and fascia. (2) Pectoralis major, (•">") Inner 

 head of median nerve, and (4) Internal cutaneous nerve. 



