The unique avian respiratory system

What makes the avian respiratory system so special? In an interview with dvm360 about one of her lectures presented at the Southwest Veterinary Symposium in Fort Worth, Texas, Lauren Thielen, DVM, DABVP (Avian Practice), provided an in-depth explanation of the mechanics of avians’ upper and lower respiratory system. As unique as their respiratory system is however, these animals’ physiology and anatomy also have some drawbacks, which Thielen also discussed in the interview.

Below is a partial transcript:

Lauren Thielen, DVM, DABVP (Avian Practice): So birds, to start, what makes them so unique with their respiratory system is they don't have a diaphragm, and so they do breathe a little bit differently, and everything's all connected through this network of what's called air sacs.

And the air sacs are just like this phenomenal thing that makes them so much more efficient at oxygen exchange than a mammal ever could be. And so what happens is, when a bird breathes, [the oxygen goes] into these air sacs­—and you can think of the air sacs as…bellows. So they don't exchange oxygen in those air sacs, but they mostly just hold the oxygen and then them holding that oxygen allows them, on their second breath, to be able to take that air and put it through their lungs and then oxygenate, and then take the oxygen from the air sacs into the rest of their body. And so, it's because of these air sacs that not only allows them to exchange oxygen so, so well, but also just makes them just so unbelievably efficient.

However, it has its drawbacks. Because these air sacs are like little balloons, or like little bellows, there's not a lot of things there as like a primary immune system, like little cells that can help get trapped debris out, or even good blood supply to allow white blood cells to really try to treat an infection, and it's because [of] you know, this efficiency of them being able to breathe; but it also has a downfall that they're more susceptible to infections just because they don't have that primary clearance mechanism.