Thyroid Diseases

Published on 16/04/2015 by admin

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Last modified 16/04/2015

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2 Thyroid Diseases

Thyroid and Parathyroid Anatomy

Thyroid Gland and Pharynx: Posterior View

Thyroid

• Thyroid typically consists of right and left lobes, connected by a midline isthmus, with an ascending pyramidal lobe in about 50% of cases.

Immediately anterior and lateral to trachea, from about 5th cervical vertebra to 1st thoracic vertebra

Medial to internal jugular veins

Anterior to common carotid arteries

Deep to infrahyoid muscles: sternohyoid (medial), omohyoid, sternothyroid (lateral)

Infrahyoid muscles embedded in pretracheal fascia, deep to investing fascia of neck (superficial layer of deep fascia)

• Connective tissue (true) capsule is continuous with the septa dividing the stroma of the gland.

• 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.

• Thyrotropin-releasing factor or hormone (TRF or TRH) from hypothalamus controls TSH release from pituitary.

• Parafollicular (C) cells secrete calcitonin.

Parathyroids

• Superior parathyroid glands usually lie between the true capsule of the thyroid and its investing surgical (false) capsule fascia.

• Inferior parathyroid glands might lie between the true and false capsules, within the thyroid parenchyma, or on the outer surface of the surgical capsule.

Vessels and Lymphatics

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