CORA CO-BRA CHIALIS 



381 



The coraco-brachialis (fig. 365). — Origin. — ^(1) By a short tendon from the tip of the cora- 

 coid process of the scapula and (2) from the tendon of the short head of the biceps. 



Insertion. — (1) By means of a strong tendon into the medial surface of the humerus im- 

 mediately proximal to the middle of the shaft, and (2) often above this also into an aponeurotic 

 band which extends from the tendon along the medial margin of the humerus, arches over the 

 tendons of the latissimus dorsi and teres major, and is attached to the lesser tubercle of the 

 humerus. When the attachment to the tubercle does not take place, the band becomes closely 

 apphed to the deep surface of the muscle. 



Structure. — From the tendons of origin, which are usually closelj'' associated, the fibre- 

 bundles take an oblique, nearly parallel, course and are attached to the aponeurotic band above 



Fig. 365. — Deep Muscles of the Froxt of the Arm. 



Pectoralis minor -f 



Short head of biceps 



Coraco-brachialis 



Long head of triceps 



Medial head of triceps 



Medial intermuscular septum 



- Lateral part of brachialis 



Insertion of biceps 



mentioned and to both surfaces of the flat tendon of insertion. This extends high into the 

 muscle. The belly of the muscle usually shows some separation into a superficial and a deep 

 portion, between which runs the musculo-cutaneous nerve. When this separation is well 

 marked, the tendon of origin of the superior fasciculus may be distinct from that of the inferior 

 fasciculus and the short head of the Diceps, and the tendon of insertion may give a separate 

 lamina to each fasciculus. 



Nerve-supply. — A branch of the musculo-cutaneous nerve, or of the brachial plexus near 

 the origin of this nerve, enters the upper third of the medial border of the muscle, and passes 

 across the constituent fibre-bundles about midway between their attachments. The nerve 

 fibres arise from the sixth and seventh cervical nerves. 



Action. — Adducts and flexes the arm at the shoulder and helps to keep the head of the 

 humerus in the glenoid fossa. When the arm has been rotated lateralward, it acts as a medial 

 rotator. 



Relations. — The coraco-brachialis is largely covered by the deltoid and pectoralis major 

 muscles. Below the inferior border of the latter it becomes superficial. Near its origin it hes 



