How do kidneys filter blood to get urine?

Question

I tried looking at diagrams of how the filtration works but I’m hitting a roadblock in my head I won’t let it go.

In: 2

Answer 1

As blood passes through your kidney, some of the water and other small molecules flow into the kidney (more importantly, out of the blood vessel) through small holes barely big enough to fit those molecules. Blood cells & like are too big to go through those holes. That water+molecules that make it to the kidney are the urine.