fish gills?

F

fuzzywuz

Registered Senior Member
fish gills separate oxygen from water....how the hell do they do it?

seems like it should be easy if a minnow can do it! anybody up on this?

fuzzywuz
 
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They seperate oxygen from water actually they don't seperate it they just use some of whats in the water extracting it as it passes over and through their gills.
 
oh...they don't actually breakdown the molecule? free O2 is floating around in the water, eh?, sort of dissolved in the water? is that it?
 
fuzzywuz said:
oh...they don't actually breakdown the molecule? free O2 is floating around in the water, eh?, sort of dissolved in the water? is that it?
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Yes, that's exactly right. It's dissolved in water along with the rest of the common gasses.

The gills work by exchange across a semipermable membrane. The exact same process our lungs use to extract O2 from the air. The only difference is in the volume of O2/CO2 exchanged and that's a direct function of the surface area available - gills are much smaller in active area than our lungs.
 
fuzzywuz said:
fish gills separate oxygen from water....how the hell do they do it?

seems like it should be easy if a minnow can do it! anybody up on this?

fuzzywuz
Click to expand...

Fresh water contains around 7% dissolved oxygen - it's less in salt water. Fish extract this using a really neat counter-current system in their gills. This means that the blood in gill capillaries is flowing in the opposite direction to water moving over the gills, so that blood with a certain concentration of oxygen in it is always encountering water with an even higher concentration of oxygen. The outcome of this is that it maintains a concentration gradient from water to gills, so that oxygen can diffuse from the water into the bloodstream along the total length of the gill. This maximises the amount of oxygen the fish can get out of the water.
 
Light said:
The only difference is in the volume of O2/CO2 exchanged and that's a direct function of the surface area available - gills are much smaller in active area than our lungs.
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Isn't it also a function of the amount of oxygen that's available in the medium to be exchanged? More oxygen molecules come into contact with one square inch of lung tissue than with one square inch of gill tissue because there are more oxygen molecules in the air that comes in contact with the lungs than in the equivalent amount of water. Water is, after all, mostly water.

This is the reason that whenever a species of air-breathing vertebrate completely adapts to the water and retrofits itself to an aquatic life, it kicks ass. Mammals and birds metabolize a lot more oxygen than an equivalent sized fish so their bodies are stronger and faster pound per pound. Being warm-blooded is a great advantage too. That's why dolphins can kick the crap out of sharks and why seals and penguins catch fish so easily. I guess there are quite a few aquatic reptiles, such as alligators and sea turtles. They're cold-blooded but they're lung breathers so they're still pretty successful in the marine food chain as long as they stay in warm climates. Still, an alligator hasn't got a prayer in a fight with a dolphin.
 
Fraggle Rocker said:
Isn't it also a function of the amount of oxygen that's available in the medium to be exchanged? More oxygen molecules come into contact with one square inch of lung tissue than with one square inch of gill tissue because there are more oxygen molecules in the air that comes in contact with the lungs than in the equivalent amount of water. Water is, after all, mostly water.

This is the reason that whenever a species of air-breathing vertebrate completely adapts to the water and retrofits itself to an aquatic life, it kicks ass. Mammals and birds metabolize a lot more oxygen than an equivalent sized fish so their bodies are stronger and faster pound per pound. Being warm-blooded is a great advantage too. That's why dolphins can kick the crap out of sharks and why seals and penguins catch fish so easily. I guess there are quite a few aquatic reptiles, such as alligators and sea turtles. They're cold-blooded but they're lung breathers so they're still pretty successful in the marine food chain as long as they stay in warm climates. Still, an alligator hasn't got a prayer in a fight with a dolphin.
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Yes, that's all very true. :) Also, keep in mind that being cold-blooded also has it's advantages as well. The lower metabolism requires less food. So things are pretty well suited to their environment.
 
Didn't someone develop an underwater breathing machine that used some sort of gill technology? I thought I had read about it but cant find it.

It seems plausible to me that we could make a synthetic gill that we operate using our natural breathing underwater. It would be cool to be able to breathe underwater with no time limits or heavy scuba gear.
 
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