Subclavius

Naming: -

/sub-KLAY-vee-us/

The part (Sub) means below [inferior] so this means under the clavicle.

General: -

It is a small muscle that lay under the clavicle bone covered by the pectoralis major. The muscle is almost on the horizontal line when the arm is in the anatomical position. It covers the subclavian groove which contain arteries,
veins and nerves if the clavicle were to fracture.

Supply: -

- Blood supply of this muscle comes from the Clavicular Branch of the Thoracoacromial Trunk (a branch of the Axillary Artery) and the Suprascapular Artery (a branch of the Thyrocervical Trunk).

- Nerve supply comes from nerve to the subclavius (root value C5 and 6), which arises from the upper trunk of the brachial plexus.

Origin & Insertion: -

-Origin: it attaches to the first rib near its junction with the costal cartilage.

-Insertion: the head attaches to the floor of the subclavian groove on the inferior surface of the clavicle.

Motion & Action: -

(Depresses the clavicle at sternoclavicular joint)

The subclavius anchors and depresses the clavicle, stabilizing it in movements of the upper limb. It also helps resist the injury of the clavicle via helping to stop dislocations at the sternoclavicular (like when pulling hard to start a lawn mower engine.

In The Field Notes: -

Testing the subclavius: the subclavius is a deep muscle so it is hard to test its action without hurting the patient.

Relations: -

The subclavius is located in-between the clavicle and the
first rib.
The subclavius is inferior to the pectoralis major.
Inferior to the subclavius are the brachial plexus of nerves and the subclavian artery and vein.
The subclavius is located within the deep front arm line myofascial meridian.

Sources: -

- Moore - Clinically Oriented Anatomy 7th Edition (699).
- Joseph E Muscolino - The Muscular System Manual: The Skeletal Muscles of the Human Body
Book 4th edtion (109-110).
-Nigel Palastanga & Roger Soames Anatomy and Human Movement Structure and Function 6th edition (58-59).