THE ANTERIOR THORACIC REGION 



459 



of origin from the sternum pass down to the lowermost part of this superficial 

 lamina of the tendon and extend as low as 'ne tendon of the Deltoid and join with 

 it. The deep lamina of the tendon receives the attachment of the lower half 

 of the sternal portion and the deeper part of the muscle from the costal cartilages. 

 These deep fibres, and particularly those from the lower costal cartilages ascend, 

 the higher turning backward successively behind the superficial and upper ones, 

 so that the tendon appears to be twisted. The deep lamina reaches higher on 

 the humerus than the superficial one, and from it an expansion is given off which 

 covers the bicipital groove and blends with the capsule of the shoulder-joint. 

 From the deepest fibres of this lamina at its insertion an expansion is given off 

 which lines the bicipital groove of the humerus, while from the lower border 

 of the tendon a third expansion passes downward to the fascia of the arm. Between 

 the posterior surface of the tendon of the Great pectoral and the anterior surface 

 of the long head of the Biceps there is usually a bursa (bursa m. pectoralis majoris). 



COSTOCORACOID 

 LIGAMENT 



CORACOID 

 PROCESS 



PECTORALIS 

 MINOR 



SHORT HEAD 

 OF BICEPS 



THORACIC BRANCH OP 

 ACROMIOTHORACIC 

 ARTERY AND EXTER- 

 NAL ANTERIOR 

 THORACIC NERVC 



FIG. 348. Costocoracoid membrane. 



Relations. By its superficial surface, with the integument, the superficial fascia, the Platysma, 

 some of the branches of the descending cervical nerves, the mammary gland, and the deep 

 fascia; by its deep surface: its thoracic portion, with the sternum, the ribs and costal cartilages, 

 the costocoracoid membrane, the Subclavius, Pectoralis minor, Serratus magnus, and the 

 Intercpstals; its axillary portion forms the anterior wall of the axillary space, and covers the 

 axillary vessels and nerves, the Biceps brachii and Coracobrachialis muscles. Its upper border 

 lies parallel with the Deltoid, from which it is separated by a slight interspace in which lie the 

 cephalic vein and humeral bianeh of the acromial thoracic artery. Its lower border forms the 

 anterior margin of the axilla, being at first separated from the Latissimus dorsi by a considerable 

 interval; but both muscles gradually converge toward the outer part of the space. 



