As air enters the nasal cavity through the nostrils, it is warmed and moistened by mucous membranes elipsis
Organ system involved in
respiration. In humans, the
diaphragm and, to a lesser extent, the muscles between the ribs generate a pumping action, moving air in and out of the lungs through a system of pipes (conducting airways), divided into upper and lower airway systems. The upper airway system comprises the nasal cavity (
see nose),
sinuses, and
pharynx; the lower airway system consists of the
larynx,
trachea, bronchi, bronchioles, and alveolar ducts (
see pulmonary alveolus). The blood and
cardiovascular system can be considered elements of a working respiratory system.
Seealso thoracic cavity.
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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
