Diagrammatic view of sagittal and transverse views of the pharyngeal regions of a human embryo during the fifth week of gestation, showing the endodermal pharyngeal pouches and mesodermal pharyngeal arches. Diagrams show the embryonic origin of the thyroid gland and parathyroid glands. Migration of the thyroid gland and parathyroid glands (anterior view) is shown in . Diagram illustrates various abnormalities which can occur during embryonic development. Each diagram is not drawn to relative scale.