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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.
@umbra21 - Even the way our bodies react to infections is ridiculous if you ask me. I mean, you basically get debilitating pain and lots of mucus that makes it impossible to sleep and which doesn't really serve much purpose.
It might help to clear the infection, but it might just as easily harm you more and it makes it impossible to sleep, so that stops you from healing as fast as you otherwise might.
If you can't tell, I'm recovering from a nasal infection so I'm a little bit annoyed about it. I hope that medical science can figure out a way to stop it from happening one day.
@pleonasm - I knew a kid who could make milk come out of his eyes if he wanted, so that doesn't surprise me. I really think in some ways the body isn't all that well designed.
I mean if you think about how many people choke to death on food that simply went down the wrong way, you'd think there was a better way to arrange the throat and the larynx so that you aren't always in danger of that.
It's one of the most compelling arguments for evolution that I know of, because an intelligent creator would have picked up that kind of error right away!
It always amazes me how huge the nasal cavity is, since it feels like such a small space most of the time, and particularly when I've got a cold.
I mean, it's essentially the same size, if not bigger than the inside of your mouth.
What's even weirder is that it's attached to all the other parts of your body around there, including your eyes, which is why you get a runny nose when you've been crying.
I read a story recently where a kid was told by his teacher to lean back when he had a nose bleed and the blood started to form in the corners of his eyes, scaring everyone in the class.
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