When you think about it, it's truly amazing how our bodies inhale oxygen and exhale carbon dioxide. This is possible thanks to the respiratory system. This system in the body is what allows us to breathe and continue our lives. The average human breathes fifty million times in their lifetime! Structure affects the functioning of this complex and wonderful system that keeps us alive. It all starts with the nose. The fundamental elements of the respiratory system are the lungs, nose, trachea, diaphragm and alveoli. When we inhale, the diaphragm below the lungs relaxes, causing the lungs to expand, letting in air from outside. We breathe air through our noses and mouths. Small, fine hairs in our nose, called cilia, filter the air for foreign particles and also wet and warm the air. Indeed, cold and dry air can irritate the lungs. The warm air then circulates down our throat and into the trachea. However, in the gorge, there are two passages. One for food and the other for air. A small flap of flesh called the epiglottis opens and closes to allow air but not food to pass through. Then the air passes through the trachea to the lungs. The trachea is one of the most crucial parts of the respiratory system. It is lined with 15 to 20 C-shaped cartilaginous rings so that it does not collapse and block the passage of air. Once the warm air passes through the trachea, it enters the lungs. The lungs have two sides, the left lung and the right lung. The left lung has three lobes and the right lung has two. Within these five lobes there are branches called bronchi and small tubes called bronchioles that branch off from the bronchi, and then these bronchioles end in tiny clusters of air sacs called alveoli. The alveoli are the small...... middle of paper ...... with clean, pure air. The human body is the most complex and intelligent organism on planet Earth. The accompanying organ systems are marvelous and breathtaking. One of the most important systems is the respiratory system, as you have read, and without it we could not survive. We will never stop breathing until we die and that, in fact, is a truly incredible feat. Works Cited “THE RESPIRATORY SYSTEM”. Respiratory system. MJ Farabee, May 18, 2010. Web. January 22, 2014. “Body Systems.” : Respiratory system. Franklin Institute, nd Web. January 22, 2014. “The respiratory system”. -NHLBI, NIH. National Heart, Lung, and Blood Institute, July 17, 2012. Web. January 24, 2014. “Respiratory system disorders.” Respiratory system disorders. McGraw Hill, and Web. January 23, 2014. Taylor, Tim. "Respiratory system." Inner body. InnerBody, and Web. January 26. 2014.