MIKKEL JUUL JENSEN / SCIENCE PHOTO LIBRARY MIKKEL JUUL JENSEN / SCIENCE PHOTO LIBRARY
Upper respiratory tract. Computer illustration of a profile section of a human head showing the upper respiratory tract and salivary glands (pale yellow). Air enters the nostrils and is filtered and warmed as it travels through the nasal cavity (upper centre). The nasal cavity meets the oral cavity (centre) at the throat to form the pharynx. The air then travels into the trachea (wind pipe, left), over the larynx (voice box), and then down into the lungs (not seen). Behind the trachea is the oesophagus (food pipe).
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