The airway and its functions

The main goals of the respiration are to provide oxygen to the tissues and to remove carbon dioxide. To achieve these goals, respiration can be divided into four major functions. They

1. Pulmonary Ventilation. Means the inflow and out flow of air between the atmosphere and the lung alveoli.
2. Diffusion, of oxygen and carbon dioxide between the alveoli and the blood
3. Transport of oxygen and carbon dioxide in the blood and body fluids to and from the body’s tissue cell
4. Regulation of ventilation and other focets of respiration

The upper airway consists of the nose, mouth, pharynx, and larynx. The larynx opens into the trachea, which in turn branches into two bronchi, enter into both lungs. The airway beyond larynx can be divided into two zones

Conducting zone

Extends from the top of the trachea to the beginning of the respiratory bronchioles

Functions

Provide low resistance pathway for air flow

Defends against microbes, toxic chemicals, and other foreign matters

Respiratory Zone

Extend from the respiratory bronchioles to the alveoli and is the region where gases exchange with blood. The inner surface of the airway down to the end of the respiratory bronchioles contains cilia, glands and epithelial cells, secrets mucus which keep the lungs clear of particulate matter and bacteria that enters body with dust particles. Another protective mechanism against infection is provided by the macrophages that exist in the airway and alveoli, these macrophages engulf and destroy inhaled particles and bacteria that have reached alveoli.

Reference 

Guyton, A & Hall, J. (2006).Text book of Medical Physiology.11^th Edition. Elsevier Saunders