# 13.43: Excretion

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### What do you do with your waste?

Toxic waste must be disposed of properly or there can be serious consequences. Now, your waste should not be as colorful or toxic as shown here (if it is, get yourself to a doctor as soon as possible), but it still needs to be removed from you. And that is the role of the excretory system. The excretory system gets rid of waste and excess water.

## Excretion

If you exercise on a hot day, you are likely to lose a lot of water in sweat. Then, for the next several hours, you may notice that you do not pass urine as often as normal and that your urine is darker than usual. Do you know why this happens? Your body is low on water and trying to reduce the amount of water lost in urine. The amount of water lost in urine is controlled by the kidneys, the main organs of the excretory system.

Excretion is the process of removing wastes and excess water from the body. It is one of the major ways the body maintains homeostasis. Although the kidneys are the main organs of excretion, several other organs also excrete wastes. They include the large intestine, liver, skin, and lungs. All of these organs of excretion, along with the kidneys, make up the excretory system. The roles of the excretory organs other than the kidney are summarized below:

• The large intestine eliminates solid wastes that remain after the digestion of food.
• The liver breaks down excess amino acids and toxins in the blood.
• The skin eliminates excess water and salts in sweat.
• The lungs exhale water vapor and carbon dioxide.

## Summary

• Excretion is the process of removing wastes and excess water from the body. It is one of the major ways the body maintains homeostasis.
• Organs of excretion make up the excretory system. They include the kidneys, large intestine, liver, skin, and lungs.
• ## Review

• What is excretion?
• List organs of the excretory system and their functions.

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