JOHN BAVOSI / SCIENCE PHOTO LIBRARY JOHN BAVOSI / SCIENCE PHOTO LIBRARY
Thyroid gland and a microscopic view. Illustration of the thyroid gland in the neck, with associated blood vessels, on a background of thyroid cells. At lower centre is the two-lobed thyroid gland positioned on the trachea (windpipe, white); it is supplied with thyroid blood vessels by the main carotid arteries (red) and jugular veins (blue) of the neck. Behind this is the cellular structure of the thyroid. It is an endocrine gland that secretes hormones which regulate energy levels and metabolism in the body. Follicles (light blue) consist of epithelial cells that secrete thyroid hormone as a pool of stored colloid (pink). This hormone is secreted into the blood when necessary.
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