Subclavian Artery - Regional Approach and Mnemonic
The subclavian arteries are a pair of large arteries in the thorax that supply blood to the thorax, head, neck, shoulder and arms.
On the left side of the body the subclavian comes directly from the aortic arch whereas on the right side it arises from the brachiocephalic trunk. Both course above the cervical pleura towards the anterior scalene muscle and through the posterior scalene gap (between the anterior and medial scalene muscles). It enters the axilla between the first rib and the clavicle and becomes the axillary artery. During its course it gives off numerous branches:
The Thoracic Region
The following branches arise medial to the scalenus anterior muscle:
- The first artery is the vertebral artery which ascends until it reaches the vertebral column at the transverse foramen of the sixth or seventh cervical vertebra.
- Second is the internal thoracic artery which runs in the opposite direction to the vertebral artery behind the sternum and costal cage. It branches off into three smaller arteries:
- The superior epigastric artery arises and runs below the costal margin, entering the rectus sheath.
- The pericardiophrenic artery accompanies the phrenic artery at the level of the fourth cervical vertebra and helps supply the pericardium.
- The musculophrenic artery supplies the upper musculature of the diaphragm.
- The third artery is the thyrocervical trunk which gives off four branches as it ascends:
- The inferior thyroid artery ascends, makes a loop behind the common carotid artery and courses towards the backside of the thyroid crossing the recurrent laryngeal nerve. It branches off arteries to the larynx (inferior laryngeal artery), infrahyoid muscles and prevertebral muscles and many more smaller ones to the surrounding structures.
- The ascending cervical artery is next and ascends along the phrenic nerve at the level of the fourth cervical vertebra.
- The transverse cervical artery divides into a superficial and deep branch.
- The superficial branch runs superficially in the lateral cervical region and then under the trapezius muscle (together with the accessory nerve). The deep branch branches off into two smaller arteries, one of which follows the dorsal scapular nerve along the medial border of the scapula. The suprascapular artery courses above the scapula in front of the anterior scalene muscle and behind the clavicle. It anastomoses with the scapular circumflex and thoracoacromial arteries (via the acromial branches).
The Muscular Region
The costocervical trunk arises behind the anterior scalene muscle and divides into two main branches:
- The supreme intercostal artery is the highest of all intercostal arteries and supplies the upper two intercostal spaces, the deep neck and back muscles, the skin of the back and the vertebral canal.
- As the trunk descends it gives rise to the deep cervical artery between the first rib and the seventh cervical vertebra which supplies the deep neck musculature.
The Cervical Region
Very often the deep branch of the transverse cervical artery arises directly from the subclavian artery lateral to the anterior scalene muscle. It is then referred to as the dorsal scapular artery. In this case it passes through the brachial plexus, usually through the upper and superior trunk.
One smart and funny way to remember the correct order and names of the most important branches of the subclavian artery:
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- Vertebral artery
- Thyrocervical trunk
- Inferior thyroid artery
- Superior cervical artery
- Suprascapular artery
- Costocervical trunk
- Supreme intercostal artery
- Deep cervical artery