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DrRob t1_iyf88wl wrote

Excellent explanations elsewhere in the thread. For me, the 'Oh wow!' factoid is, the gas exchanging surface area in your lungs is the size of a tennis court. Remember that with each heartbeat, just as much blood gets pumped to your lungs (from the right ventricle) as to the rest of your body (from your left ventricle), so there's a whole lotta blood being pumped through a network spreading it as thin as a single red blood cell, over a freakin' tennis court!

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MyFaceSaysItsSugar t1_iyfcvx7 wrote

Yes, a lot of people don’t realize this but we, just like fish, need oxygen to dissolve in fluid before we can use it. But oceans and lakes don’t have very much dissolved oxygen compared to air, so what our lungs have done is create what is basically a pond the size of a tennis court and folded it up to fit in our chest so that there’s this massive surface available for oxygen to dissolve through, and then hemoglobin binds to that oxygen as fast as it’s getting dissolved, which makes space for more oxygen to get dissolved as new air is inhaled.

Whale kidneys look a lot like lungs for this same reason. Whales need to filter a bunch of salt out of the water they ingest as they eat while still holding onto that water, so they need a lot more surface area in their kidneys to produce super concentrated urine that’s kind of an orangey brown color.

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