The are those parts of the Respiratory System through which air flows, to get from the external environment to the Alveoli .
The airway begins at the mouth or nose, and accesses the Trachea via the Pharynx . The trachea branches into the left and right main Bronchi at the Carina , situated at the level of the second Thoracic Vertebra . The bronchi branch into large Bronchioles , one for each Lobe of the Lung . Within the lobes, the bronchi further subdivide some 20 times, ending in clusters of alveoli.
The Epithelial surfaces of the airways contain Cilia . Inhaled particles stick to Mucus (secreted by goblet Cell s) which is continuously removed from the airways by these cilia. The airway epithelium also secretes a watery fluid upon which the mucus can ride freely. The production of this fluid is impaired by the disease Cystic Fibrosis . Macrophages are present in the airways. These cells protect the airways from infection by engulfing inhaled particles and Bacteria .
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