The main organ involved in breathing is the lungs. They are essential for respiration, allowing the exchange of oxygen and carbon dioxide between the air and the bloodstream. Lungs are located in the thoracic cavity and are protected by the rib cage. When a person inhales, air enters the lungs through the trachea, which branches into the bronchi and further into smaller bronchioles, ending at the alveoli, tiny air sacs where gas exchange occurs. Oxygen from the inhaled air passes into the bloodstream, while carbon dioxide from the blood is expelled when the person exhales, making lungs vital for life.