Subclavius muscle

Classification and structure

The subclavius muscle belongs to the group of superficial chest muscles (mm. thoracis). By origin, it is an upper limb muscle.

• Origin: originates from the 1st rib in the region of its cartilage.
• Insertion: attaches to the inferior surface of the middle third of the clavicle (clavicula), where the groove for the subclavius muscle (sulcus m. subclavii) is located.

Topography and Fascial Sheaths

The muscle, together with the clavicle, serves as an osteomuscular landmark of the axillary fossa. On a sagittal section of the subclavian region, the structures are arranged in the following sequence:

1. Bony structures: clavicle.
2. Muscles: subclavius muscle, pectoralis major (m. pectoralis major), pectoralis minor (m. pectoralis minor), and serratus anterior (m. serratus anterior) muscles.
3. Fascia and fatty tissue: subpectoral space, pectoral fascia, clavipectoral fascia, axillary fascia, endothoracic fascia, and fatty tissue of the axillary fossa.
4. Internal structures: parietal pleura and the axillary artery and vein.

Clavipectoral fascia (fascia clavipectoralis) forms osseo-fibrous sheaths for two muscles: the pectoralis minor and subclavius muscles. The pectoral fascia (fascia pectoralis) superiorly attaches to the fascia of the subclavius muscle and to the superficial layer of the deep cervical fascia. Posterior to the clavicle, part of the 5th layer of the cervical fascia covering the anterior scalene muscle attaches to the 1st rib.

Relation to the Neurovascular Bundle

The subclavius muscle covers the origin of the axillary artery (a. axillaris), which is the direct continuation of the subclavian artery. The origin of the axillary artery is located beneath the clavicle at the clavipectoral triangle (trigonum clavipectorale).

The axillary artery is divided into three parts:

1. Part I — from the clavicle to the superior border of the pectoralis minor muscle.
2. Part II — posterior to the pectoralis minor muscle.
3. Part III — from the inferior border of the pectoralis minor muscle to the inferior border of the pectoralis major muscle.

For Part I of the axillary artery, the following relations are noted: it lies on the superior slips of the serratus anterior muscle, anteriorly covered by the clavipectoral fascia; anteromedially to it lies the subclavian vein (v. subclavia), and anterolaterally — the trunks of the brachial plexus (plexus brachialis).

Blood Supply, Innervation, and Function

• Blood supply: thoracoacromial artery (a. thoracoacromialis) and superior thoracic artery (a. thoracica superior).
• Innervation: subclavian nerve (n. subclavius), C5–C6.
• Function: pulls the clavicle inferiorly and medially, stabilizes the sternoclavicular joint.

Class and exam questions

What else to study on this topic

• Clavipectoral fascia (fascia clavipectoralis)
• Axillary artery (a. axillaris)
• Pectoralis major and minor muscles
• Topography of the axillary fossa

Other topics in the "Anatomical Structures" section

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