The upper respiratory system is made up of everything from the nose to the trachea, including the nasal cavity, frontal, maxillary, and sphenoidal sinuses, ethmoidal air cells, and the larynx. The bronchi and bronchioles airways, lungs, and alveoli make up the lower respiratory tract. The upper and lower respiratory system work together to exchange carbon dioxide for oxygen in the body.
On inhalation, air moves through the nose and travels to the nasal cavity. This cavity is behind and slightly above the nose. As air passes through this structure, it is warmed or cooled as necessary so that it is within one degree of body temperature. Short, dense hairs called vibrissae clean the air. The material filtered from the air moves into the esophagus and then the stomach.
The next stop in the upper respiratory system is the ethmoidal air cells and the frontal, maxillary, and sphenoidal sinuses. These are small cavities lined with mucous membranes that surround the nasal cavity. The larynx, or voice box, is also part of this system. Located in the neck, the larynx is used for breathing, producing sound, and preventing food from entering the trachea. The larynx is home to the vocal cords, which are necessary for speech.
Located between the trachea and larynx is the epiglottis. The epiglottis closes during swallowing, to prevent food from entering the trachea. It is made of cartilage, and covered in mucous membrane. While not protecting the trachea during swallowing, the epiglottis points upward, toward the tongue.
The trachea is the last section of the upper respiratory system. It is also called the windpipe. The trachea connects the larynx to the lungs. It is lined with mucous producing cells that trap pollen and other inhaled particles to prevent them from entering the lungs. The trachea contracts when coughing to force air up, rather than down into the lungs.
The upper respiratory system is susceptible to infection, especially things like the common cold, otis media, sinusitis, tonsillitis, pharyngitis, and laryngitis. These illnesses typically last between seven and ten days. Symptoms include sneezing, pressure in the face, nasal congestion, low-grade fever, runny nose, cough, and sore throat. Treatment typically includes plenty of rest and fluids, along with treatment for pain and fever with over the counter medications. Antibiotic resistance has led to a decrease in the use of antibiotics for most minor upper respiratory infections.