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Parafollicular cells, also called C cells, are neuroendocrine cells in the thyroid. They are called C cells because the primary function of these cells is to secrete calcitonin. [1] They are located adjacent to the thyroid follicles and reside in the connective tissue. These cells are large and have a pale stain compared with the follicular cells.
Calcitonin is a 32 amino acid peptide hormone secreted by parafollicular cells (also known as C cells) of the thyroid (or endostyle) in humans and other chordates [5] in the ultimopharyngeal body. [6] It acts to reduce blood calcium (Ca 2+), opposing the effects of parathyroid hormone (PTH). [7]
At the microscopic level, there are three primary features of the thyroid—thyroid follicles, thyroid follicular cells, and parafollicular cells, first discovered by Geoffery Websterson in 1664. [14] Follicles. Thyroid follicles are small spherical groupings of cells 0.02–0.9mm in diameter that play the main role in thyroid function. [4]
The endocrine glands belong to the body's control system. The hormones which they produce help to regulate the functions of cells and tissues throughout the body. Endocrine organs are activated to release their hormones by humoral, neural, or hormonal stimuli. Negative feedback is important in regulating hormone levels in the blood.
Calcitonin-producing parafollicular cells are also found along the basement membrane of the thyroid follicle, interspersed between follicular cells; and in spaces between the spherical follicles. Parafollicular cells can be distinguished from follicular cells based on their lighter staining cytoplasm using H&E.
The sensors for the second are the parafollicular cells in the thyroid gland. The parathyroid chief cells secrete parathyroid hormone (PTH) in response to a fall in the plasma ionized calcium level; the parafollicular cells of the thyroid gland secrete calcitonin in response to a rise in the plasma ionized calcium level.
When the concentration of calcium rises, the parafollicular cells of the thyroid gland increase their secretion of calcitonin, a polypeptide hormone, into the blood. At the same time, the parathyroid glands reduce the secretion of parathyroid hormone (PTH), also a polypeptide hormone, into the blood.
Mo cell (or M cell) motilin secretion other hormones secreted: vasoactive intestinal peptide, substance P, alpha and gamma-endorphin, bombesin: Thyroid epithelial cell: Thyroid gland cells Parafollicular cell: Parathyroid chief cell: Parathyroid gland cells Oxyphil cell Alpha cell: glucagon secretion Pancreatic islets (islets of Langerhans ...