Thyroid Gland

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The Anatomy of the Thyroid Gland

The thyroid gland itself is sheathed in a fibrous capsule which has both an inner and outer layer. The posterior external layer is continuous with the carotid sheath, and the anterior external layer is continuous with the lamina pretrachealis fasciae cervicalis. At the front of the thyroid gland there are the infrahyoid muscles and the sternocleidomastoid muscle which may be implicated in some conditions of neck and jaw pain. On the posterior side of the lobes, between the inner and outer capsule, lie the parathyroid glands. Nerves which innervate the thyroid consist of the (parasympathetic) superior laryngeal nerve and the recurrent laryngeal nerve. The neck contains a plethora of lymphatic tissue and both the lateral deep cervical lymph nodes and the pre- and paratracheal lymph nodes lie near to the thyroid.

Thyroid Gland Anatomy
Thyroid Gland Anatomy

Of all of the endocrine glands in the body, the thyroid is the largest, weighing between 18grams and 60grams in an adult, and increasing in size during pregnancy. It is supplied by blood in the superior thyroid artery which branches from the external carotid artery, and the inferior thyroid artery which stems from the thyrocervical trunk. The brachiocephalic trunk may also supply the thyroid with blood via the thyroid ima artery. The superior thyroid veins, draining into the internal jugular vein, and the inferior thyroid veins draining into the plexus thyroideus impar and then the braciocephalic vein take the blood back to the heart from the thyroid.

Last Updated: 12/18/2010