The respiratory system consists of various structures that facilitate breathing and gas exchange. Key components include the nose, trachea, bronchi, and lungs. Air enters through the nose or mouth, travels down the trachea, and branches into the bronchi, which lead to the lungs. Inside the lungs, tiny air sacs called alveoli allow oxygen to enter the bloodstream while removing carbon dioxide. The diaphragm, a muscle beneath the lungs, plays a crucial role in inhalation and exhalation by contracting and relaxing to change the pressure in the chest cavity.