2 Thyroid Diseases
Thyroid and Parathyroid Anatomy
Thyroid
• Thyroid typically consists of right and left lobes, connected by a midline isthmus, with an ascending pyramidal lobe in about 50% of cases.
• Location
• Surgical (false) capsule lies external to the true capsule and is derived from the pretracheal fascia.
• Of the overlying strap muscles, the sternohyoid is most superficial, overlying the sternothyroid and thyrohyoid.
• Thyroid follicular (epithelial/principal) cells secrete thyroxine (T4) and triiodothyronine (T3), regulated by TSH receptors.
Vessels and Lymphatics
Arterial Supply
• Superior thyroid arteries arise bilaterally from the external carotid arteries at, above, or below the bifurcation of the common carotid.