All human beings need to breathe to stay alive. Oxygen present in the air helps to break down the food absorbed by the body. This breakdown of food results in the release of energy that is important for us to work or play. We breathe in the oxygen from the air and breathe out carbon dioxide. The organs that help in the process are parts of the respiratory system.
The respiratory system is the system of the body that deals with breathing. The nose, mouth, windpipe, diaphragm and lungs are the organs involved in respiration. When we breathe, the body takes in the air through the nose or mouth and down through the windpipe or trachea.
The trachea is a pipe consisting of rings of cartilage. It divides into two tubes called bronchi. These carry air into each lung. Inside the lung, the tubes divide into smaller and smaller tubes called bronchioles. At the end of each of these tubes are small air sacs called alveoli.
Capillaries, which are small blood vessels with thin walls, are wrapped around these alveoli. The walls are so thin and close to each other that the air easily seeps through. Oxygen passes through into the bloodstream and carbon dioxide, in the bloodstream, seeps through into the alveoli. It is then removed from the body when we breathe out.
The diaphragm is the muscle that controls the breathing process. As the diaphragm flattens, it causes the chest to expand and air is sucked into the lungs. When the diaphragm relaxes, the chest collapses and the air in the lungs is forced out.