Subclavius muscle

The Subclavius is a small triangular muscle, placed between the clavicle and the first rib. Along with the pectoralis major and pectoralis minor muscles, the subclavius muscle makes up the anterior wall of the axilla.

Origin and insertion
It arises by a short, thick tendon from the first rib and its cartilage at their junction, in front of the costoclavicular ligament.

The fleshy fibers proceed obliquely lateralward and generally upward, to be inserted into the groove on the under surface of the clavicle between the costoclavicular and conoid ligaments.

Action
The Subclavius depresses the shoulder, carrying it downward and forward. It draws the clavicle inferiorly as well as anteriorly.

The Subclavus protects the underlying brachial plexus and subclavian vessels from a broken clavicle - the most frequently broken long bone.

Variations
Insertion into coracoid process instead of clavicle or into both clavicle and coracoid process. Sternoscapular fasciculus to the upper border of scapula. Sternoclavicularis from manubrium to clavicle between Pectoralis major and coracoclavicular fascia.