Reptilian lungs are much simpler than most mammalian, and chameleons have some of the thinnest-walled lungs overall. Additionally, their lungs have purposes other than respiration/transfer of oxygen and carbon dioxide; mainly to assist increasing their apparent body size for intimidation purposes as well as positive buoyancy in some cases. The cranial component of the lung (nearest my fingers in the video) have most of the respiratory structure while the caudal 2/3rds inflate for the other reasons.
The reason I want to show the video is for educational purposes, as words sometimes are not enough to describe the incredible delicacy of a chameleon lung. I have typically told my clients to imagine a rubbery soap bubble or the thinnest sheet of plastic wrap possible. By gross exam this was a healthy lung, obviously deflated at the necropsy. By inflating it and revealing the overall architecture I hope that it can be better appreciated why issues such as pneumonia, trauma or even parasitic infections can be devastating in reptiles even after a successful treatment. Any damage to the walls may result in perforation or scarring that can be rapidly fatal. It is unfortunately not uncommon for reptiles with pneumonia to be treated and show great improvement (and may truly be free of any infectious agent), only to suddenly die some time later due to the damage done when ill.
This video was taken during the necropsy of an approximately 18 month old female Veiled chameleon who likely died from recent inadequate calcium supplementation. I had examined and treated her for pinworms during prior appointments with all adequate husbandry. She had an extremely varied insect diet and "classic" dusting protocol with Repashy products until 2 months prior when she was given to a friend for continued care during the original owner's travel. However, although she was kept outdoors in sunny Florida the new caregiver stopped all dusting. She was full of eggs at the time of death and had previously laid virgin clutches both 2 and 5 months prior. Neurologic tremors were noted in her limbs by the caregiver that stopped after a single dose of NeoCalGlucon, however she was found dead the next day. Therefore this is also a lesson on the need for adequate calcium intake, particularly in gravid chameleons.