The respiratory system includes the nose, mouth, pharynx, larynx, trachea, bronchi, lungs, and diaphragm. It introduces oxygen into the body and releases carbon dioxide through a multi-step process. Air enters through the nose or mouth and is filtered and humidified before passing through the pharynx and larynx into the trachea. The trachea branches into smaller bronchioles that terminate in alveoli in the lungs where gas exchange occurs. The diaphragm and lungs work together to inhale oxygenated air and exhale carbon dioxide.