The bronchioles divide into smaller branches called terminal bronchioles. According to an article published by Healthline Medical Team, this branching system of bronchi and bronchioles is called the “bronchial tree” because when looked at upside down, the group looks like a tree that branches in different directions (“bronchial tree”). The tree-like structure allows air to flow to all parts of the lungs. At the end of the terminal bronchioles there are air sacs called alveoli where oxygen exchange occurs. The alveoli fill every time we breathe. A baby's first breath is so difficult because these alveoli fill from a collapsed state. All of these branching pieces are found within a series of “large spongy organs” called lungs (Taylor); although they are not huge, the surface area of ​​a pair of lungs can cover a tennis court. Each lung has several lobes: the right lung has three, but the left lung only has two to make room for the heart. Both lungs are enclosed in pleural cavities bordered by a thin protective tissue called the pleura. The last part of the respiratory system is the respiratory muscles. Without