It is the largest of the endocrine glands. It is located on the anterior neck, below the cartilages of the larynx, trachea cons it covers the first ring.
It consists of two lateral lobes united to each other by a narrow portion, the isthmus. Its overall shape reminds that of H. Its texture is firm, his grayish pink, its average weight 20 to 25 g.
Histologically, the thyroid gland appears as formed by the juxtaposition of many cell blocks which we give the name of thyroid vesicles. Each vesicle is formed and thyroid:
* the center is occupied by a body more or less voluminous gummy substance, yellowish, devoid of any cell. This substance is called colloid;
* each cluster of colloid is surrounded by a single layer of polyhedral epithelial cells. These are cells that develop the colloid to have in reserve in the center of vesicles;
* between thyroid vesicles are very rich capillary network. The appearance of thyroid cells and the amount of colloid contained in the vesicles vary depending on the degree of activity of the gland. (more…)