Embryology Practice Exam

Think about what each pharyngeal arch becomes. The fourth arch contributes to the laryngeal skeleton and many of the muscles associated with the pharynx and larynx. In particular, the thyroid cartilage of the larynx is derived from the fourth arch, so this arch becomes structures of the larynx including the thyroid cartilage. The other options don’t fit because the sixth arch supplies other laryngeal components and the pulmonary arteries, the first arch forms the jaw, and the inner ear and facial expression muscles arise from other arches. So the fourth arch truly forms the larynx and thyroid cartilage.