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Parafollicular cells are derived from pharyngeal endoderm. [2] [3] Embryologically, they associate with the ultimopharyngeal body, which is a ventral derivative of the fourth (or fifth) pharyngeal pouch. Parafollicular cells were previously believed to be derived from the neural crest based on a series of experiments in quail-chick chimeras.
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]
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 .
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]
Thyroid gland Follicular cell; Parafollicular cell [3] Parathyroid gland. Parathyroid chief cell; Oxyphil cell; Thymus gland. Thymic epithelial cell; Hindgut/cloaca.
superior parathyroid glands and ultimobranchial body which forms the parafollicular C-Cells of the thyroid gland. Musculature and cartilage of larynx (along with the sixth pharyngeal arch). Nerve supplying these derivatives is Superior laryngeal nerve.
Medullary thyroid cancer is a form of thyroid carcinoma which originates from the parafollicular cells (C cells), which produce the hormone calcitonin. [1] Medullary tumors are the third most common of all thyroid cancers and together make up about 3% of all thyroid cancer cases. [2] MTC was first characterized in 1959. [3]
Calcitonin, produced by the parafollicular cells (C cells) of the thyroid gland in response to rising blood calcium levels, depresses blood calcium levels by inhibiting bone matrix resorption and enhancing calcium deposit in bones. Excessive secretion cause hyperthyroidism and deficiency cause hypothyroidism.
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