The thyrocervical trunk is one of the 3 branches of the first part of the subclavian artery and gives off numerous branches to supply viscera of the neck, the brachial plexus, neck muscles and the scapular anastomosis.
The trunk arises lateral to the vertebral artery from the anterosuperior wall of the subclavian artery adjacent to the anterior scalene muscle in the lower anterior neck and ascends as a short, stout trunk before giving rise to four branches: (see mnenomic)
the inferior thyroid artery is the largest and most important branch of the trunk. It ascends medial and posterior to the lower pole of the thyroid gland superficial to the pretracheal fascia. It sends multiple small branches through the pretracheal fascia to supply the larynx, trachea, esophagus, and thyroid and parathyroid glands, as well as adjacent muscles, hence is known as the primary visceral artery of the neck.
the suprascapular artery traverses inferiorly and laterally superficial to the anterior scalene muscle and phrenic nerve before crossing the third part of the subclavian artery and the cords of the brachial plexus. It then courses posterior to the clavicle to supply the posterior scapular muscles, where it anastomoses with the rich scapular arterial plexus (scapular anastomosis). It may arise directly from the third part of the subclavian artery.
the ascending cervical artery is a small artery that ascends medial to the phrenic nerve on the prevertebral fascia. It contributes many small spinal branches into the intervertebral foramina of the neck as well as giving off multiple small muscular branches to the lateral muscles of the upper neck.
the transverse cervical artery is a short artery that further bifurcates into the superficial and deep branches, both which course superficially and laterally across the phrenic nerve and anterior scalene muscle. They then cross or pass through the trunks of the brachial plexus, supplying branches to their vasa nervorum. Its branches are:
- the superficial cervical artery which passes anterior to the trapezius muscle adjacent to the spinal accessory nerve (CN XI).
- the dorsal scapular artery which accompanies the dorsal scapular nerve, coursing deep to the levator scapulae and rhomboid muscles, supplying both and contributing to the scapular arterial anastomoses. It may arise directly from the third or the second part of the subclavian artery.