Ultimobranchial body/ ultimobranchial gland
Left ultimobranchial body of a laying hen (HE): C cells
The secretory cells or C cells comprise the major part of the epithelial component of the ultimobranchial body. C cells are frequently organized into strands and cords but also single cells and groups of two to three cells can be recognized. They lie in close association with blood capillaries.
C cells produce calcitonin which plays a role in the avian calcium metabolism, together with parathyroid hormone, gonadal steroids and vitamin D. The exact mechanism and the exact function of calcitonin in birds however is not yet fully understood.