Blood Supply and Venous Drainage
Arteries of Thyroid Gland
The rich blood supply supply to the thyroid gland comes from the superior thyroid and inferior thyroid arteries and, occasionally, from the thyroid ima artery. These arteries lie between the fibrous capsule and the loose fascial sheath:
- Superior Thyroid Artery - Usually, arise from the first branches of the external carotid artery. This artery descend to the superior poles of the gland, pierces the pretracheal layer of the deep cervical fascia and divide into anterior and posterior branches.
- Inferior Thyroid Artery - The largest branches of the thyrocervical trunk, arising from the subclavian artery. It run superomedially posterior to the carotid sheath to reach posterior aspect of the thyroid gland. The
- Thyroid Ima Artery - Approximately 10% of people has this artery. It arise either from the brachiocephalic trunk, arch of aorta, right common carotid artery, subclavian or internal thoracic artery (see picture above). This small artery ascends on the anterior surface of trachea, which it supplies, and continues to the isthmus of the thyroid gland.
The right and left superior and inferior thyroid arteries anastomoses extensively within the thyroid gland, ensuring its supply while providing potential collateral circulation between the subclavian and the external carotid arteries.
Venous Drainage
There are three pairs of veins that usually drain the thyroid plexus of vein on the anterior surface of the thyroid gland and trachea. The three pairs are superior thyroid veins, middle thyroid veins and inferior thyroid veins.
- Superior thyroid veins - Accompany the superior thyroid arteries and drain the superior poles of the gland.
- Middle thyroid veins - drain the middle of the lobes.
- Inferior thyroid veins - drain the inferior poles.