Lungs anatomical differences & Respiration

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Anatomical differences, between the right and left lung

The anatomical differences, between the right and left lung, start at the embryonic phase. Around the 33rd day, the true lung primordium divides into two unequal in size buds called the main bronchi (The Swiss virtual campus, 2008). The smaller left bud grows lateral to the esophagus and further divides into two lobes, while the bigger right bud grows parallel and caudal to the esophagus and will further divided in three lobes (The Swiss virtual campus, 2008). Thus, the asymmetry and differences of the lungs in the adult are established.

While some of the differences are grossly seen, ones are more subtle. For example:
Each lung has three borders (anterior, inferior, and posterior), but the anterior border of the left lung deviates to the left due to the presence of the cardiac notch in which the pericardium is exposed; while on the right lung, the anterior border runs almost vertical (O'Rahilly, Müller, Carpenter, & Swenson, 2004; Gray, 2000).

The lungs also have three surfaces (costal, medial, and diaphragmatic) with slight differences in the medial and diaphragmatic surfaces (O'Rahilly et al., 2004)
The diaphragmatic surface of the right lung has a deeper concavity than the left lung due to the presence of the liver left lobe (O'Rahilly et al., 2004; Gray, 2000). This makes the right lung 2.5 cm shorter and gives broader look, due to the inclination of the heart to the left, compare to the left lung (Gray, 2000; O'Rahilly et al., 2004). The shape of the right lung gives a total capacity greater than the left and consequently it will weigh more (Gray, 2000). On average, the right lung weighs about 625 gm. and the left 567 gm. depending on the amount of blood or serous fluid they may contain (Gray, 2000).

The mediastinal surface of both lungs has a deep concavity to accommodate the heart. This cardiac impression is deeper on the left lung than on the right due to the position of the heart (Gray, 2000). The mediastinal surface also has a triangular impression or hilus where the structures that form the root enter and leave the lungs (Gray, 2000; O'Rahilly et al., 2004).

The position of the roots of each lung differs due to the location on the thorax of each lung. The root of the right lung lies behind the superior vena cava and part of the right atrium, and below the azygos vein; while the root of the left lung passes beneath the aortic arch and in front of the descending aorta (Gray, 2000; Johnson, 2003).

While the roots of both lungs carry the same structures, there is a difference in the bronchi and the bronchial vessels (O'Rahilly et al., 2004; Gray, 2000; Johnson, 2003).
Running at a 25 degrees angle, the right bronchus is only 2.5 cm long from the bifurcation of the trachea when it divides in ...