Anterior Thorax and Neck -
LO 9
9. Describe the location of the thyroid and parathyroid glands. Arrange details regarding function and vascular supply & drainage of these glands.
The thyroid gland has two lobes connected by a central isthmus, and sits between the C5-T1 vertebra. Nearly 50% of people have an accessory (pyramidal) lobe, which varies in size and typically connects the isthmus of the thyroid gland to the hyoid bone (Moore et al., 7th edition).
The thyroid gland is an endocrine gland - meaning it secretes hormones and is ductless. The thyroid gland secretes thyroid hormones (controls rates of tissue metabolism) and calcitonin (important in calcium homeostasis).
Arterial supply of the thyroid gland
Superior thyroid a.
Typically the first branch of the external carotid a.
Inferior thyroid a.
Branch of thyrocervical trunk of the 1st part of the subclavian a.
Typically crosses the recurrent laryngeal n. deep to the thyroid gland in the vicinity of the larynx
Clinical consideration: when ligating this artery during a thyroidectomy, care must be taken to not damage the recurrent laryngeal n., which innervates most intrinsic laryngeal muscles and inferior larynx.
Venous drainage of the thyroid gland
Superior thyroid v.
Middle thyroid v.
Inferior thyroid v.
Parathyroid glands may be found in a variety of locations, but are typically on the posterior aspect of the thyroid gland. There are typically four parathyroid glands (a superior pair and inferior pair), but there may be more or fewer. The superior parathyroids are the most constant in size and position. Parathyroid glands may be supplied by either set of thyroid arteries (as determined by location), but typically the inferior thyroid aa. supply the parathyroids. The parathyroid glands are also endocrine, and produce parathyroid hormone (PTH).
