<prompt> Thyroid medullary cells that produce calcitonin develop from:Ultimobranchial bodyFloor of the primitive pharynx3rd pharyngeal archLung buds  <response>: Neural crest derivatives from the ultimobranchial body give rise to thyroid medullary C cells. It produces calcitonin. The C cells are interspersed throughout the thyroid gland. ALSO KNOW The ultimobranchial body arises from bilateral ventral swellings of the 4th pharyngeal pouches and gets integrated into the thyroid where it forms the parafollicular cells or C-cells for the production of calcitonin. Ref: Harrison, E-18, P-2911. 