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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.
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 .
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 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]
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.
Thyroid gland Follicular cell; Parafollicular cell [3] Parathyroid gland. Parathyroid chief cell; Oxyphil cell; Thymus gland. Thymic epithelial cell; Hindgut/cloaca.
Melanocytes appear as clear cells when in the stratum basale of the skin, and Langerhans' cells appear as clear cells in the stratum spinosum. [2] C cells, more commonly referred to as parafollicular cells are type of cell found in the thyroid gland which stain clear using H&E.
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]