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The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the isthmus (pl.: isthmi).
The hypothalamic–pituitary–thyroid axis (HPT axis for short, a.k.a. thyroid homeostasis or thyrotropic feedback control) is part of the neuroendocrine system responsible for the regulation of metabolism and also responds to stress. As its name suggests, it depends upon the hypothalamus, the pituitary gland, and the thyroid gland.
The thyrocervical trunk is a branch of the subclavian artery. [1] It arises from the first portion of this vessel, between the origin of the subclavian artery and the inner border of the anterior scalene muscle.
Zuckerkandl's tubercle is a pyramidal extension of the thyroid gland, present at the most posterior side of each lobe. [1] [2] Emil Zuckerkandl described it in 1902 as the processus posterior glandulae thyreoideae. [3] Although the structure is named after Zuckerkandl, it was discovered first by Otto Madelung in 1867 as the posterior horn of ...
After enveloping the thyroid gland, it is prolonged in front of the trachea to meet the corresponding layer of the opposite side. The pretracheal layer of the deep cervical fascia passes in front of the carotid sheath (i.e., common carotid artery , internal jugular vein , and vagus nerve ) and in front of the cervical viscera ( larynx ...
A hypoplastic gland may develop higher in the neck or even in the back of the tongue. A gland in the wrong place is referred to as ectopic, and an ectopic gland at the base or back of the tongue is a lingual thyroid. Some of these cases of developmentally abnormal glands result from genetic defects, and some are "sporadic," with no identifiable ...
Thyroid follicular cells form a simple cuboidal epithelium and are arranged in spherical thyroid follicles surrounding a fluid filled space known as the colloid. The interior space formed by the follicular cells is known as the follicular lumen .
TSH (with a half-life of about an hour) stimulates the thyroid gland to secrete the hormone thyroxine (T 4), which has only a slight effect on metabolism. T 4 is converted to triiodothyronine (T 3), which is the active hormone that stimulates metabolism. About 80% of this conversion is in the liver and other organs, and 20% in the thyroid ...