Choana is:
Posterior nares Nasal cavity: Nasal fossae are two irregular cavities extending from the mucocutaneous junction with the nasal vestibule in front(anterior nares) to the junction with the nasopharynx behind(posterior nares or choanae) Ref.Dhingra 5/e,p 150.6/e,p 135.
anterior nares
Posterior nares
Tonsils
Larynx
Nose and paranasal sinuses