
Introduction:
The thyroid gland consists of two lobes, and it is the largest (25 g) adult endocrine gland. The isthmus connects the two lobes of the thyroid gland. The thyroid is located at the neck, adjacent to the trachea and beneath the larynx. It has a butterfly shape and is covered around the trachea. It is composed of thyroid follicles, which is covered by follicular cells. The follicular cells secrete thyroid hormones (TH) such as triiodothyronine (T3) and thyroxine (T4). The thyroid gland releases TH into the bloodstream. Thyroid-stimulating hormone (TSH) regulates hormones (T3 and T4) secretion from the thyroid. TH raises the metabolic rate by promoting the adequate supply of blood and oxygen. Also TH increases the heart rate and respiratory rate and IS involved in the breakdown of carbohydrate and fat to provide energy. TH regulates appetite, alertness, secretion of growth hormone, body growth, reproduction, and circulatory system. Abnormal secretion of thyroid hormones may cause thyroid problems.

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Chapter 17 Solutions
EBK ANATOMY & PHYSIOLOGY: THE UNITY OF
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