Consists of (in descending order) - the nose, mouth, nasal passages, nasal pharynx, pharynx, larynx, trachea, bronchi, bronchioles, air sacs (alveoli) of the lungs, and muscles of respiration
US Department of Labor, Glossary of Terms - Occupational Safety & Health Administration, OSHA Office of Training and Education, Construction Safety and Health Outreach Program, Washington, D.C., USA 1996. https://www.osha.gov/doc/outreachtraining/htmlfile s/hazglos.html, (OSHA/ Const - Amer) {614}