The human respiratory system consists of several key structures that facilitate breathing. Air enters through the nose or mouth, travels down the trachea, and branches into the bronchi, which lead to the lungs. Inside the lungs, smaller airways called bronchioles end in tiny air sacs known as alveoli, where gas exchange occurs. The primary function of the respiratory system is to supply oxygen to the body and remove carbon dioxide. The diaphragm, a muscle located beneath the lungs, plays a crucial role in inhalation and exhalation by contracting and relaxing to change the pressure in the chest cavity.