Kidneys Filter Impurities

blue purple and white medical illustration of a human kidney cross section

Biological Strategy

Humans

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Image: Mohammed Haneefa Nizamudeen / iStock / Some rights reserved

Capture, Absorb, or Filter Organisms

Many living systems must secure organisms for food. But just as one living system must capture its prey to survive, its prey must escape to survive. This results in capture and avoidance strategies that include trickery, speed, poisons, constructed traps, and more. For example, a carnivorous plant called the pitcher plant has leaves formed into a tube that collect water. Long, slippery hairs within the tube face downward. When insects enter the tube seeking nectar, they lose their footing and slide inside, unable to climb out and escape being eaten and digested by the plant.

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Capture, Absorb, or Filter Chemical Entities

Living systems often require chemical elements and chemical compounds, including complex sugars, proteins, and odor-making compounds, to perform critical activities. These compounds exist in various states–solid, liquid, and gas–and are ubiquitous in soil, water, and air. This requires that living systems not only have ways to capture, absorb, or filter them, but also ways to differentiate among them, selecting those that are valuable or harmful. For example, mangrove trees live with their roots in salty water and sediments. Various mangrove species have different strategies for removing salt from the water they take in so that their tissues can use the fresh water.

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Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Kidneys of humans filter impurities by use of a dual membrane system.

Image: Roxbury-de /

Image: Piotr Micha? Jaworski /

1. 1.Renal pyramid 2. 2.Interlobar artery 3. 3.Renal artery 4. 4.Renal vein 5. 5.Renal hylum 6. 6.Renal pelvis 7. 7.Ureter 8. 8.Minor calyx 9. 9.Renal capsule 10. 10.Inferior renal capsule 11. 11.Superior renal capsule 12. 12.Interlobar vein 13. 13.Nephron 14. 14.Minor calyx 15. 15.Major calyx 16. 16.Renal papilla 17. 17.Renal column

“Using a system based on the human body’s s – the ultimate in water recycling technology – Singapore and Orange County, CA have developed schemes that will use a dual membrane process to recycle domestic waste water (sewage) to levels that approach the quality of distilled water. Like the kidney, these recycling plants use two membranes, one with larger holes to remove micro-organisms such as protozoa and bacteria that cause infection, while the second separates salt from water.” (Courtesy of the Guild)

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