The anatomy of the airway consists of the upper and the lower airways. The upper airway starts at the mouth and Nares and ends at the _________?

The airway is divided into two different anatomical locations; the upper airway and lower airway.  The upper airway starts where air enters the body - the nose (Nares) and the mouth.  Air will pass through the nose and is filtered and warmed before passing through the remainder of the upper airway and entering the lower airway.  The upper airway ends at the Cricoid cartilage, the distal end of the larynx. The Thyroid cartilage is located at the proximal end of the larynx.  Reference: Jeremy P. T. Ward; Jane Ward; Charles M. Wiener (2006). The respiratory system at a glance. Wiley-Blackwell. pp. 11–. ISBN 978-1-4051-3448-4. Retrieved 26 April 2010.