Lungs are comprised of many different structures. The image on this page depicts the trachea, bronchi, and the several lobes of the left and right lungs. The trachea (windpipe) is the passageway that allows air to travel to and from the lungs.
The left and right lungs are very different. We have already noted that the mainstem bronchi are different, with the left mainstem bronchus being long and thin, while the right mainstem bronchus is short and fat. The left lung has only two lobes. There is a left upper lobe (LUL) and a left lower lobe (LLL).
The inferior lobe is the smaller of the two lung lobes and is situated below and behind the fissure and comprises almost the entire base, a large portion of the costal surface and a greater part of the posterior border. The lobe that is missing or is not present in the left lung when compared to the right lung is the middle lobe.