ABSTRACT
This chapter shows that oxygen from the atmosphere diffuses from a high concentration in the alveoli to a lower concentration in pulmonary circulation. The respiratory system consists of the airways, the lungs, the muscles of respiration and the areas of the nervous system which control the rate and depth of ventilation. The airways are divided into the upper and lower respiratory tract at the larynx. Air enters the larynx through the epiglottis which protects the glottis and lower respiratory tract when swallowing occurs. The upper respiratory tract consists of the nasal cavity, the mouth and the pharynx. Air is inhaled through the nose and is filtered, warmed and humidified as it passes through the nasal conchae and makes its way to posterior chamber of the nasal cavity and the upper part of the pharynx – the nasopharynx. The pharynx, oral cavity and nasal cavity also act as resonating chamber that helps to provide the distinctive sound quality of the voice.
