any structural anomaly of any oral opening of the nasopalatine (incisive) canal; it is located in the maxilla in the incisive fossa, midline in the palate posterior to the central incisors, at the junction of the medial palatine and incisive sutures; it can be single or multiple; it transmits the greater palatine artery and vein from the oral to the nasal cavity and the nasopalatine nerve in the opposite direction