Figure 1: Upper airway delineating margins and landmarks those were proposed according to the study by Anandarajah S.34: Superior: The line passing from the anterior nasal spine to posterior nasal spine (ANS to PNS) extended to the posterior wall of the pharynx, Inferior: The passing line from the anterior-superior edge of the fourth cervical vertebrae to the menton (CV4 to Me) Anterior: The anterior wall of the pharynx, Posterior: The posterior wall of the pharynx, Laterally: Lateral pharyngeal walls. Tip of soft palate (U) and mental spines (MS) forming the U-MS line