Corpus: Subclavius muscle

The subclavius muscle is a narrow, short muscle that lies between the first rib and the clavicle.

The subclavius muscle originates from the first rib and the first costal cartilage via a strong, short tendon. Its muscle fibers then extend obliquely laterally and upward. The muscle inserts on the underside of the clavicle, specifically in the middle and lateral third, between the costoclavicular ligament and the conoid ligament.

The subclavius muscle is innervated by the subclavian nerve, which arises from the supraclavicular part of the brachial plexus, specifically from spinal segments C5 and C6.

The subclavius muscle functions to pull the lateral end of the clavicle downward (caudally). Along with the pectoralis minor muscle, it helps keep the subclavian vein open by stretching the clavipectoral fascia. Additionally, when the trapezius muscle lifts the thorax, the subclavius muscle stabilizes the clavicle by anchoring it to the first rib.

Scar tissue shortening of the subclavius muscle can contribute to thoracic outlet syndrome (TOS), a condition that compresses the nerves and blood vessels passing through the thoracic outlet.