The lungs are the large, spongy, paired organs which reside in the thoracic cavity. Protected by the structure of the rib cage, each lung runs from the Just above the clavicle down to the diaphragm.

The mediastinum is the vacant area between the lungs which segregates the two organs. The heart resides in this cavity. With the exception of the primary bronchi, the lung’s functioning systems are encased within their structure.


Each lung is designed with 4 surfaces. Each of these 4 surfaces matches the basic contour of the thoracic cavity. The medial surface (mediastinal) contains a vertical slit and is mildly concave. The slit is referred to as the hilum, and this is where the nerves, bronchi, and the pulmonary vessels pass through.

The base of the lung is the inferior surface, fits perfectly against the convex dome of the diaphragm. The apex, or the cupola, of the lung is the superior surface. It reaches above the clavicle. The costal lung surface is the portion that comes in direct contact with the membranes which cover the rib cage, and has a very broad but rounded surface.


Image: Lungs


The right and left lungs are not, in fact, identical. They are similar and appear to be nearly identical. The left lung is equipped with a cardiac dent to allow for the heart, and is just a bit smaller than the right lung. The left lung makes use of a single fissure to divide it into two separate regions, the superior lobe and the inferior lobe. The right lung uses two fissures to create the superior and inferior lobes, and then adds a middle lobe.

The pulmonary alveoli are housed within the numerous small lobules in each lung. Bronchial segments are created by these lobular divisions. Each bronchial segment is a unique entity and is supplied with its own blood. This means that a diseased portion of a lung can be surgically removed and the remainder of the lung can continue to function. The left lung is equipped with 8 individual segments while the right lung is equipped with 10 individual segments.
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