You breathe around 20,000 breaths every day on average. Breathing is a complicated process that affects every area of the body, yet being mostly a subconscious effort. When you breathe, you use the respiratory system, and the oxygen is used by your body's cells, resulting in waste in the form of carbon dioxide. The lungs are a pair of organs in the thorax (chest) that function as gas exchangers. They play an important role in maintaining the balance of oxygen and carbon dioxide in the blood. The trachea is the main airway from the throat to the bronchi. It functions as a passage for food to be swallowed or sputum to be exhaled. The esophagus is the longer portion of the trachea that leads from the pharynx to the stomach. It functions to transport food and liquid into the digestive system and absorbs nutrients while passing through it. The diaphragm is a dome-shaped muscle that separates the chest from the abdomen. It functions as a pump when you breathe in and out rapidly. The muscles of the ribcage expand and contract during inhalation and exhalation respectively. These muscles work with the muscles of the diaphragm to facilitate airflow into and out of the lungs. The nerves that control the diaphragm come from segments of the spinal cord and brain. They communicate with each other via messages passed along by various hormones, such as adrenaline and cortisol.