In most amphibians:
- The pharyngeal pouches develop into structures associated with the digestive and respiratory systems.
- The first pharyngeal pouch becomes the Eustachian tube, connecting the middle ear to the throat, which is important for hearing and pressure equalization.
- The second and third pharyngeal pouches give rise to the palatine tonsils and thymus gland, respectively, both involved in immune function.
In reptiles, birds, and mammals, including humans:
- The pharyngeal pouches undergo further modifications and become incorporated into different structures.
- In reptiles, they may contribute to the formation of the thyroid and parathyroid glands, as well as parts of the respiratory system.
- In birds and mammals, the pharyngeal pouches are more reduced and are usually not visible in adults. They may contribute to the development of certain tissues and organs during embryonic development but eventually disappear or merge with other structures.