Selective reabsorption.

Flowers in the Swell

The physiology of human kidneys are outrageously interesting. Obviously there exists complexities, but in general, simplicity seems to be the byword. This idea commands the kidneys and as a whole, human physiology, which is actually one of the most creative and simplistic things I've ever seen. Small changes affect the entire functional unit (the nephron in the case of the kidneys) which affect the entire body.

A nephron, this wacky looking thing is the fundamental functional unit of the kidneys. You actually have about a million of each of these per kidney! It looks like something I'd draw as a child.
photo from: http://www.highlands.edu

So how does the kidney filter what stays in your body and what needs to leave? Some portions of the nephron (like the proximal convoluted tubule) are pretty independent and reabsorb the same stuff in the same quantities all the time. Others do what is called selective reabsorption. Depending on variables such as hormone concentration, ion concentration in the blood, blood volume, blood pressure, and osmolarity (big word!), the kidneys can take the hint and adjust what they reabsorb back into the blood to maintain homeostasis!

For example, say you have not drunk enough water and you are becoming dehydrated. Your kidneys have cells that can sense this, and through changes in hormones which result in actual structural changes, the nephron become more porous and can reabsorb more water so you urinate less and retain more water inside your body. The reverse is also possible if you over hydrated.

We all selectively filter what happens and what we take part of in our lives. I was able to filter an extra day of climbing in and visit a canyon in the Swell I had never visited, and I can't wait to filter some more back in!

My first visit to Three Finger Canyon

The West Slabs of the desert (we called it), we cruised up the two long
easy classics of the area......

.....and then continued running along the ridge forever. Why not?

I often find that climbing in the desert is about spotting the coolest features and climbing them.
The rock is crumbly, the gear falls out, but the lines are classic. This is a nice example.