Frontonasal duct opens into:
The frontonasal duct is a communication between the frontal air sinuses and their corresponding nasal cavity. The duct is lined by mucous membrane. The duct empties into the nasal cavity middle nasal meatus through the infundibulum of the semilunar hiatus. Ref: Dhingra 6th edition, page 136.
Inferior meatus
Middle meatus
Superior meatus
Inferior meatus
Nose and paranasal sinuses