The respiratory system includes the nose, mouth, trachea, bronchi, diaphragm and lungs. It moves air in and out of the body to provide oxygen to cells and remove carbon dioxide. Air enters through the nose or mouth and travels down the trachea to the lungs. The trachea divides into bronchi that lead to smaller bronchioles and alveoli, where oxygen passes into blood and carbon dioxide leaves. Key parts include the nasal passages, which warm and filter air, the diaphragm which aids breathing, and the epiglottis which prevents food from entering the windpipe. Diseases that can impact the respiratory system include asthma, bronchitis, COPD, cystic fibrosis,