Head of a dolphin fetus, showing the pharyngeal cavity. (A) Oropharynx; (B) Laryngopharynx; (C) Nasopharynx. MRI sagittal T1 SE sequence. 10 months, dde14. 1, Isthmus of the fauces; 2, Fauces; 3, Epiglottic vallecula; 4, Piriform recess; 5, Oesophageal vestibule; 6, Intrapharyngeal orifice: 7, Oesophagus mucosa.