Trachea, bronchi, bronchioles and alveoli | Anatomy and Physiology |

Trachea, bronchi, bronchioles and alveoli The trachea, commonly known as the windpipe, is a tube about 4 inches long and less than an inch in diameter in most people. The trachea begins just under the larynx (voice box) and runs down behind the breastbone (sternum). The trachea then divides into two smaller tubes called bronchi: one bronchus for each lung. The bronchial tubes split up again to carry air into the lobes of each lung. The right lung has three lobes while the left lung has only two, to accommodate room for the heart, The lobes are filled with small, spongy sacs called alveoli, which is where the exchange of oxygen and carbon dioxide occurs. The alveolar walls are extremely thin (about 0.2 micrometers) and are composed of a single layer of tissues called epithelial cells and tiny blood vessels called pulmonary capillaries. Blood in the capillaries picks up oxygen and drops off carbon dioxide. The oxygenated blood then makes its way to the pulmonary vein. This vein carries oxygen-rich blood to the left side of the heart, where it is pumped to all parts of the body. The carbon dioxide the blood left behind moves into the alveoli and gets expelled in our exhaled breath. #LowerRespiratorySystem #LowerRespiratoryTract #StructureOfLungs