Composition of Urine

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  • 0:30 Definition of Urine
  • 0:37 Composition of Urine
  • 3:00 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

We are going to look at urine and break it down into its components. This lesson covers the amounts of measurable substances in urine and the pigments that determine urine color.

Urine

You have just arrived home from a very long day and you have to go to pee really badly. You are on a mad dash for the bathroom. There are a couple of pauses along the way to do the pee-pee dance, which keeps you from going on yourself. Finally, you get to the bathroom and with no time to spare.

You are now in the oval office and able to relax your bladder and pee. Ahhhh! What did you really just let go of though? Yes, it's urine. But what exactly is in your urine? Urine is a solution of excess water, salts, and waste products. Let's take a closer look.

What's In Urine?

We need to first remind ourselves that our kidneys make urine as they filter excess substances out of the blood. So the short answer to our question is that urine contains anything that is not needed in the blood.

It doesn't quite flow out like a waterfall, but the most abundant portion of urine is excess water. Water composes at least 95% of our urine when we are healthy. You may notice that your urine is more diluted when you drink more water and more concentrated when you drink less water. This happens because you are only getting rid of excess water. If you don't have extra water, you can't rid of it in your urine.

There are a variety of other substances that make up the other approximate 5% of urine. Some of the substances are waste products from metabolism. We will look at the estimated amounts in normal urine.

Urea is the most concentrated waste product in the urine. Urea is a nitrogen-compound, and it makes up about 2% of urine. Think of urea as the packaging that the kidneys use to get rid of excess nitrogen from the blood.

The other waste product found in a measurable amount in the urine is creatinine. Creatinine is the chemical that gets produced every time your muscles contract. If you think about how much you use your muscles in one day, then you know creatinine can build up quickly in our blood. Luckily for us, our kidneys are able to get rid of it and excrete it out in our urine. Our urine consists of approximately 0.1% of creatinine.

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