RT Book, Section A1 Lee, Grace A. A1 Masharani, Umesh A2 Lalwani, Anil K. SR Print(0) ID 55770062 T1 Chapter 42. Disorders of the Thyroid Gland T2 CURRENT Diagnosis & Treatment in Otolaryngology—Head & Neck Surgery, 3e YR 2012 FD 2012 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-162439-8 LK accesssurgery.mhmedical.com/content.aspx?aid=55770062 RD 2024/03/19 AB The normal thyroid gland is located anterior to the trachea and midway between the apex of the thyroid cartilage and the suprasternal notch (Figure 42–1). Important neighboring posterior structures include the four parathyroid glands situated behind the upper and middle thyroid lobes, and the recurrent laryngeal nerves coursing along the trachea. The thyroid consists of two pear-shaped lobes connected by an isthmus. The typical dimensions of the lobes are 2.5–4.0 cm in length, 1.5–2.0 cm in width, and 1.0–1.5 cm in thickness. Also, in about 50% of patients, a small pyramidal lobe is present at the isthmus or adjacent part of the lobes. The functional unit of the thyroid is the follicle consisting of a central collection of colloidal material (thyroglobulin) surrounded by a single layer of polarized epithelial cells.