The human respiratory system is responsible for taking in oxygen and expelling carbon dioxide. It consists of several key structures, including the nose, trachea, lungs, and diaphragm. Air enters through the nose or mouth, travels down the trachea, and into the lungs, where gas exchange occurs in tiny air sacs called alveoli. Breathing is controlled by the diaphragm and intercostal muscles, which expand and contract the chest cavity. This process allows fresh air to enter the lungs and helps remove waste gases. Proper functioning of the respiratory system is essential for maintaining overall health and energy levels.