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.

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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.

Most of the other substances are salts, also called electrolytes, that the kidneys need to release in order to maintain the proper water/electrolyte balance. Chloride can be found in urine with a concentration of around 0.6%, sodium at around 0.1%, and potassium at about 0.6%. The other salts that are found in urine are there in extremely small amounts.

We also have pigments in our urine that give color to the urine. Urine from a healthy person will appear light yellow to dark amber in color. The color is determined by the amounts of the three pigments urochrome, urobilin, and uroerythrin.

Other substances found in urine in trace amounts include hormones, amino acids, and metabolites.

Lesson Summary

We covered urine, which is a liquid solution of excess water, salts, and wastes. You should know that water is the most abundant portion of urine, at 95%. The wastes products in urine include urea at 2% and creatinine at 0.1%.

Urine also contains 0.6% chloride, 0.1% sodium, and 0.6% potassium. These are electrolytes commonly referred to as salts. The last thing contained in urine that we can readily see are the urine pigments. These include urochrome, urobilin, and uroerythrin. There are traces of amino acids, hormones, and metabolites in urine as well.

Learning Outcomes

Complete the lesson and then assess your ability to:

  • List the components of urine
  • Note the percentages of salts and waste products in urine
  • Name substances that are present only in trace amounts