The author effects a descriptive analysis of the different glandular thyroid stage, especially of side sketches, that taking as a basis our observations, we consider and demonstrate that they are originated only starting from the fourth bursae, because the parathyroids glands are ectodermic deriiated proceeding from the epicardic branchial placode, situated on the dorsal surfaces of the fourth epic blastic sulcus, both approaches opposite to classically accepted.