There are several different parts of the respiratory system that make it possible for people to breathe in oxygen and exhale carbon dioxide. Air is first inhaled through the nose and mouth. It then passes through the pharynx, larynx, and trachea, and at the bottom of the trachea the air moves into one of two bronchi that lead into the lungs. There it passes through progressively smaller structures known as bronchioles and alveoli, which then pass the oxygen to the blood via nearby capillaries and also pick up carbon dioxide to be exhaled. The final part of the respiratory system is the diaphragm, a muscular structure below the lungs that helps them move air in and out.
The first parts of the respiratory system, which allow air to enter the body, are the nose and the mouth. The nose in particular is important in the breathing process for two reasons. As air passes through the nostrils, hairs there filter out any particles it may contain. It then moves to the nasal passages, where it is warmed and humidified, making it easier for the body to process.
After entering the body through the nose or mouth, air travels through several other parts of the respiratory system on its way to the lungs. It goes through the pharynx in the throat and then moves to the larynx, a structure sometimes called the voice box or vocal cords, which allow a person to speak. It then moves down the trachea, or windpipe, which splits at the bottom into two tubes — the bronchi — that lead into the lungs.
The lungs and the structures they contain are critical parts of the respiratory system, as they allow the body to absorb the oxygen in the air being breathed, and also to rid the body of the waste product carbon dioxide. After entering the lungs, the bronchi branch out into smaller passageways called bronchioles, which further branch into small, thin-walled clusters of sacs named alveoli. The alveoli are surrounded by small capillaries that pick up oxygen from them to carry to the rest of the body and also pass carbon dioxide to them for exhalation.
Though it does not directly process air, the diaphragm is another of the important parts of the respiratory system. The diaphragm is a powerful muscle that lies at the bottom of the chest cavity, separating it from the digestive organs. It contracts and expands to help draw air in and out of the lungs.
