The lungs (pulmones) is the organ where the breathing happens, or in other words, an exchange of oxygen from the air, and carbon dioxide from the blood. The lungs are placed in thoracic cavity and are connected through the pleura. The right lung is a little bigger then the left, because the heart is placed in the left side of the chest. The lungs consists of about 300 millions of little vesicles, called aveolies.