It arises by a short, thick tendon from the first rib and its cartilage at their junction, in front of the costoclavicular ligament.[1]
The fleshy fibers proceed obliquely superolaterally, to be inserted into the groove on the under surface of the clavicle.
Innervation
The nerve to subclavius (or subclavian nerve) innervates the muscle. This arises from the junction of the fifth and sixth cervical nerves, from the superior/upper trunk of the brachial plexus.
Variation
Insertion into coracoid process instead of clavicle or into both clavicle and coracoid process. Sternoscapular fasciculus to the upper border of scapula. Sternoclavicularis[3] from manubrium to clavicle between pectoralis major and coracoclavicular fascia.[1] Rarely, the subclavius may be missing entirely.[4]
Function
It depresses the lateral clavicle, acts to stabilize the clavicle while the shoulder moves the arm. It also raises the first rib while lowering the clavicle during breathing.
The subclavius protects the underlying brachial plexus and subclavian vessels from a broken clavicle—the most frequently broken long bone.
Additional images
Subclavius muscle (shown in red). Humerus and scapula are shown in semi-transparent. Animation.
Subclavius muscle (shown in red).
Anterior surface of sternum and costal cartilages.
Left clavicle. Inferior surface.
The axillary artery and its branches.
The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front.
