WLOGY 



I 



muscles, and to the parietes of the thorax, and anastomoses with the internal mam- 

 mary and intercostal arteries. 



2. The thoracoacromial artery (a. thoracoacromialis; acromiothoracic artery; tho- 

 racic axis) is a short trunk, which arises from the forepart of the axillary artery, 

 its origin being generally overlapped by the upper edge of the Pectoralis minor 

 Projecting forward to the upper border of this muscle, it pierces the coracoclavicular 

 fascia and divides into four branches pectoral, acromial, clavicular, and deltoid. 

 The pectoral branch descends between the two Pectorales, and is distributed to 

 them and to the mamma, anastomosing with the intercostal branches of the internal 

 mammary and with the lateral thoracic. The acromial branch runs lateralward 

 over the coracoid process and under the Deltoideus, to which it gives branches; 

 it then pierces that muscle and ends on the acromion in an arterial network formed 

 by branches from the transverse scapular, thoracoacromial, and posterior humeral 

 circumflex arteries. The clavicular branch runs upward and medialward to the 

 sternoclavicular joint, supplying this articulation, and the Subclavius. The deltoid 

 (humeral) branch, often arising with the acromial, crosses over the Pectoralis minor 

 and passes in the same groove as the cephalic vein, between the Pectoralis major 

 and Deltoideus, and gives branches to both muscles. 



3. The lateral thoracic artery (a. thoracalis lateralis; long thoracic artery; external 

 mammary artery) follows the lower border of the Pectoralis minor to the side of 

 the chest, supplying the Serratus anterior and the Pectoralis, and sending branches 

 across the axilla to the axillary glands and Subscapularis ; it anastomoses with the 

 internal mammary, subscapular, and intercostal arteries, and with the pectoral 

 branch of the thoracoacromial. In the female it supplies an external mammary 

 branch which turns round the free edge of the Pectoralis major and supplies the 

 mamma. 



4. The subscapular artery (a. subscapularis) the largest branch of the axillary 

 artery, arises at the lower border of the Subscapularis, which it follows to the in- 

 ferior angle of the scapula, where 

 it anastomoses with the lateral 

 thoracic and intercostal arteries 



^ ^^ ^ descending branch 



of the transverse cervical, and 

 ends in the neighboring muscles. 

 About 4 cm. from its origin it 

 gives off a branch, the scapular 

 circumflex artery. 



The Scapular Circumflex Artery 

 (a. circumflexa scapula; dorsalis 

 scapula* artery) is generally larger 

 than the continuation of the sub- 

 scapular. It curves around the 

 axillary border of the scapula, 

 traversing the space between 

 the Subscapularis above, the 

 Teres major below, and the long 

 head of the Triceps laterally 

 (Fig. 524); it enters the infra- 

 spinatous fossa under cover of 

 the Teres minor, and anasto- 

 moses \vith the transverse scap- 

 ular artery and the descending branch of the transverse cervical. In its course 

 it gives off two branches: one (infrascapular) enters the subscapular fossa beneath 

 the Subscapularis, which it supplies, anastomosing with the transverse scapular 



Desc. br. of 

 transverse cervical 



FIG. 524. The scapular and circumflex arteries. 



