Lungs : Definition
The lungs are two organs located in the thorax and through them makes the breath. They are separated by an area called the mediastinum, the area which houses the heart, trachea, esophagus and blood vessels. The air reaches the lungs through the trachea divides into two main bronchi, right and left, for each lung. In the lungs, each primary bronchus divides, like the branches of a tree in increasingly finer lines: secondary bronchi, bronchioles and alveolar ducts, to reach some small sacs called alveoli.
The walls of the alveoli contain many small blood vessels where gas exchange occurs during respiration. The lungs function is to carry out gas exchange with the blood, so the alveoli are in close contact with capillaries. In the alveoli that the passage of oxygen from the air to the blood and the passage of carbon dioxide from the blood into the air. The inspiration is absorbed oxygen from the air entering the lungs, and expiration carbon dioxide is expelled outside.
The right lung is divided by two fissures (major and minor) in three parts, called lobes (upper, middle and bottom). The left lung has two lobes (upper and lower) separated by a fissure (fissure higher). This is because the heart has an oblique angle to the left and from back to front, reducing the volume of the left lung. The lungs are covered by a membrane called the pleura. During breathing facilitates the pleura lungs constrict and expand.