Expansion
Superior comes from above, inferior climbs from below
Mnemonic
“Superior with superior, inferior with recurrent”, which is the rule that matters in surgery:
- Superior thyroid artery, from the external carotid, runs with the external branch of the superior laryngeal nerve. Ligate it close to the gland to spare the nerve
- Inferior thyroid artery, from the thyrocervical trunk, runs with the recurrent laryngeal nerve. Ligate it away from the gland, laterally
“Superior artery, superior nerve, tie it high; inferior artery, recurrent nerve, tie it low.”
Venous drainage does not follow the arteries: superior and middle thyroid veins to the internal jugular, but the inferior thyroid vein to the brachiocephalic, and a thyroidea ima artery is present in a small minority, arising from the arch or brachiocephalic, which is a hazard in tracheostomy.
Expansion
- Superior thyroid artery - branch of the external carotid artery
- Inferior thyroid artery - branch of the thyrocervical trunk from the subclavian artery