Dear Jeff,
The worst thing about being an anthropomorphic cat is that I have to scoop my own litter box. It’s a real drag.
I asked my friend Henry Mroch why we need to pee in the first place. He’s a doctor at Washington State University. He teaches medical students about the organs that make urine—called kidneys.
He told me that most people have two kidneys. Each one is about the size of your fist. They sit near your back, right under your ribcage.
Each kidney attaches to a tube called a ureter. Those tubes take urine to a storage pouch—called the bladder. When you pee, another tube called the urethra moves the urine from the bladder out of your body.
Your kidneys’ main job is to get rid of metabolic waste. That’s all the leftover stuff from the chemical reactions your body does to make or use energy.
That waste forms inside the 40 trillion cells of your body. Inside each one, you have tiny, bean-shaped organelles called mitochondria. Their job is to change the energy stored in the food you eat into energy your body can use. That’s how your body powers everything. You need that energy to make your muscles move, your heart beat, and more.
Your body needs a way to get all that metabolic waste out of your body. It’s kind of like how you need to take out the trash, so your home doesn’t fill up with garbage.
“If we don’t get rid of the waste products, then our body will get pickled with waste products, and we will get sick,” Mroch said.
So, your body uses your blood to move the metabolic waste to your kidneys. It travels in a big blood vessel called an artery to get there.
Each kidney is made up of 2 million tiny filtering units called nephrons. Mroch says they have microscopic sprinkler heads. They spray liquid blood into a series of tiny tubes. The tubes absorb anything your body can recycle—like nutrients and minerals.
All the useless or toxic waste gets mixed with extra water your body doesn’t need. That’s urine. The freshly filtered blood zooms out of your kidney through another blood vessel.
That whole system works super hard. Mroch told me that your kidneys process 180 liters of fluid every single day. If you poured all that fluid into 1-gallon milk jugs, you’d need more than 47 jugs to hold it all.
If someone’s kidneys aren’t working well enough, they need help from a doctor. They might need a machine to filter their blood. Or they could need a kidney transplant. That’s how important it is to get that waste out of your body.
Once the urine moves to your bladder, nerves in the bladder alert your brain that you need to use the bathroom. Then, you send it into the toilet—or litter box.
You could say ur-ine better shape with all that metabolic waste gone.
Sincerely,
Dr. Universe