The pulmonary organ is the LUNG, which is a four-letter word. The lungs are a pair of organs located in the chest cavity and are responsible for respiration. They take in oxygen from the air and release carbon dioxide. The lungs also help to regulate the body's temperature and pH levels. The lungs are made up of millions of tiny air sacs called alveoli, which are connected to the trachea and bronchi. The alveoli are where oxygen and carbon dioxide are exchanged between the air and the bloodstream.