Anatomy of the thryroid

In the neck Inferior to larynx Anterolateral structure

Where is it?

4 parathyroid glands

Aorta Brachiocephalic Left Common carotid Left Subclavian artery

Branches of the aorta

Dual Blood Supply

Aorta (RHS brachiocephalic Lhs direct) common carotid external carotid superior thyroid artery

(RHS brachiocephalic, LHS aorta)

Subclavian thyrocervical trunk inferior thyroid artery

Superior & middle thyroid drain to internal jugular (to subclavian to brachiocephalic)

Inferior thyroid into brachiocephalic veins

Venous drainage

Starts life on the tongue and descends via the thyroglossal duct

Embryology

Thyroglossal duct cysts

Can form anywhere along the thyroglossal duct in the midline neck.

Move on swallowing and tongue protrusion

The thyroid gland and lumps tends to move during swallowing but not always with tongue protrusion.

Histology

Increased gland growth

•high TSH•low T4

Iodine deficiency

T4TSH

+ decreased T4 secretion

Adapted from Endocrinology Physiology. SP Porterfield, Mosby

+ Increased T4 secretion

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-

Increased gland growth

•Low TSH•high T4

Graves disease

Adapted from Endocrinology Physiology. SP Porterfield, Mosby

T4TSH

TSIthyroid stimulating

immunoglobulin