In the spirit of studying & sharing the cool stuff I've learned, here's some more fun facts. This time it's all about the kidneys, which are amazing!
The kidneys filter blood through fancy little capsules called glomeruli. Most of the liquid part of the blood, plasma, is taken back up into the bloodstream, but some of it goes on for more processing. This is how urine is formed, not by the digestive tract as most people think.
There are 11.8 miles of capillaries (tiny blood vessels) scrunched up in the two million or so glomeruli we have in the kidneys. The kidneys themselves are each only about the size of your fist & the glomeruli hardly take up the most space, so this is pretty staggering!
The glomerular capillaries as they're called are the site of filtration, which is a surface area dependent process (bigger filter, more stuff filtered). Special cells hang out on these capillaries reducing the surface area for filtration from 930 square inches (10-11 sheets of paper) to about 80 square inches...which is less than the area of ONE regular sheet of paper! This incredibly small area still manages to filter every bit of our blood 60 times a day!!
Not to mention the kidney's role in regulating blood pressure, salt & water balance, potassium, calcium, acid/base balance, and quite a bit more. And the brain doesn't really get involved. Transplanted kidneys don't have nervous input for years (nerves grow back slowly), but they work just fine. The kidney "knows" how to manage all of these things all on its own! Now isn't that amazing?