Pharyngeal gill slits contribute to the formation of which structures?

• A. Pharynx, gills, and Eustachian tubes in ears
• B. Lungs and diaphragm
• C. Esophagus and stomach
• D. Trachea and bronchi

Answer: (A)

Pharyngeal gill slits are openings in the pharyngeal region that mark the pharyngeal apparatus, which differentiates into different structures as development proceeds. In fishes they persist as gill slits that support respiration. In tetrapods, these grooves and the associated pharyngeal pouches are repurposed to form parts of the throat and ear region: the pharynx itself, and the structures related to hearing such as the Eustachian (pharyngotympanic) tube that connects the middle ear to the pharynx. This is why pharyngeal gill slits contribute to the formation of the pharynx, gills, and Eustachian tubes in ears.