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# 13.46: Kidneys

Difficulty Level: At Grade Created by: CK-12
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Why is a bean-shaped organ so important?

Shown above are the isolated kidneys from many little mice. OK, they're really just kidney beans. But this is what the important kidney looks like. Why is it so important? Your kidneys filter and remove wastes from your blood.

### Kidneys and Homeostasis

The kidneys play many vital roles in homeostasis . They filter all the blood in the body many times each day and produce a total of about 1.5 liters of urine . The kidneys control the amount of water, ions, and other substances in the blood by excreting more or less of them in urine. The kidneys also secrete hormones that help maintain homeostasis. Erythropoietin , for example, is a kidney hormone that stimulates bone marrow to produce red blood cells when more are needed. The kidneys themselves are also regulated by hormones. For example, antidiuretic hormone from the hypothalamus stimulates the kidneys to produce more concentrated urine when the body is low on water.

### Summary

• The kidneys maintain homeostasis by controlling the amount of water, ions, and other substances in the blood.
• Kidneys also secrete hormones that have other homeostatic functions.

### Practice I

Use this resource to answer the questions that follow.

• http://www.hippocampus.org/Biology $\rightarrow$ Biology for AP* $\rightarrow$ Search: The Human Kidney
1. Describe the role of the kidney in maintaining homeostasis.
3. What is the function of ADH?

### Review

1. Explain how the kidneys maintain homeostasis.

Feb 24, 2012

Aug 02, 2014