What benefits do they bring? Couldn’t we just have a straight airway leading to lungs without all the nooks and crannies?
In: Biology
We don’t fully know why all the sinuses exist. The biggest theory is to reduce the weight of our skull.
My understanding is that they act as a filter for the lungs. Better to get a sinus infection than a lung infection.
They’re a convenient moisture reservoir for when you inhale. The lungs need to stay moist to continue facilitating the transfer of gases, so the sinuses add water to the inhaled air so that they don’t dry out.
So, here is the tricky thing….whatever sinuses evolved for, it happened waaaaaay before we were human. Our current arrangement is basically what we ended up with after we evolved our weird, very flat faces. So, what they do *now* may not be what they evolved for originally.
Interestingly, our frontal sinuses don’t develop until about the age of 5 or 6. So, we don’t *need* them until then. If at all. They could be relics.
We’re not 100% sure why sinuses exist
Current working theories are that they help moisturize and warm air coming into your lungs to make it easier to breath particularly in very hot and very cold environments.
They also act as a filter trapping water, dust, bacteria, and viruses in your sinuses so that they can get trapped in mucus rather than affecting the lung tissue. The idea being that a sinus infection is less harmful to you than a lung infection.
Sinuses also make your skull lighter but having air pockets rather than dense bone.
Humans are also notorious for having a weak sense of smell compared to other animals. Having sinuses may be important for capturing an analyzing smells in other animals.
This book has a fascinating chapter on sinuses if you want to read more!
Check out this book on Goodreads: Human Errors: A Panorama of Our Glitches, from Pointless Bones to Broken Genes https://www.goodreads.com/book/show/36606264-human-errors
Rhinologist here. Even after removal of all ethmoid sinuses (small ones between the eyes) there is no discernible side effect. Agree with the others here that they are just evolutionary remnants. Although they can be useful crumple zones in a crash.
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