about gills, lungs scuba divers, and aualungs. Please do not laugh, this is from the newbie
Mark
because I am from the school long time ago, I have forgot the answer.
Anyway; here is the question. The fish, e.g. the shark, that exists
already for millions years if not more, has the ability to extract
oxygen from water? Is that a correct statement? It is possible I make a
wrong assumption so the rest of my questions dont even apply.
Anyway; my understanding is that oxygen gets somehow extracted, gets in
the blood stream, is carried to viatl organs that need it (or organism
functions) that use it?
So; the question is ; if the stupid shark can do it, why with all the
technical knowledge in engineering we can not build a machine that does
it and can be used instead of aqualung?
Shane
three points
1. Lungs can already do this. The movie "The Abyss" has a short
section of a mouse being immersed in a special liquid that allows
oxygen exchange in the lungs, the mouse survives. My understanding is
that this was not special effects, but actual footage. Google will
find you a number of references.
2. There exist already, membrane filters that can do this, however my
guess is the surface area required to produce enough oxygen for an
active human, makes the unit unsuitable for most underwater purposes.
3. What is wrong with the aqualung? it does the job well. Or to put it
another way, why do you think there is a need to produce some other
device to replace the aqualung?
Inez
I imagine it would be dangerous to hook your circulatory system up to a
set of artifical gills. Plunging into salt water with a big IV needle
in your arm might be unpleasant.
Windy
Mark wrote:
> I have a question. Probably the answer is very simple, it is just
> because I am from the school long time ago, I have forgot the answer.
>
> Anyway; here is the question. The fish, e.g. the shark, that exists
> already for millions years if not more, has the ability to extract
> oxygen from water? Is that a correct statement? It is possible I make a
> wrong assumption so the rest of my questions dont even apply.
Depends what you mean by extract: oxygen diffuses passively to blood in
the gills in the same way it does in our lungs.
> Anyway; my understanding is that oxygen gets somehow extracted, gets in
> the blood stream, is carried to viatl organs that need it (or organism
> functions) that use it?
>
> So; the question is ; if the stupid shark can do it, why with all the
> technical knowledge in engineering we can not build a machine that does
> it and can be used instead of aqualung?
There is very little oxygen in water (by volume) compared to air, and
it takes more energy to move around water, so it would probably be very
hard to make it worthwhile.
-- w.
Inez
r norman
All aquatic organisms have the ability to extract oxygen from the
water in which they live. The simple fact, though, is that there is
really only a very small about of oxygen dissolved in water. Sea
water normally contains only about 5 to 10 ml of oxygen per liter.
Air contains 210 ml of oxygen per liter. In addition, water is very
massive and viscous and so is hard to move through small channels over
the respiratory surface whereas air is very light and easy to move.
So we simply can't get enough oxygen directly from the water and is it
far easier, cheaper, and more effective to carry oxygen or air tanks
down with us. Fish have very highly specialized gills that are
extremely effective at extracting oxygen. Still, they spend a large
fraction of their metabolic rate just getting enough oxygen. We air
breathers spend only a trivial fraction of our metabolic rate in
breathing. The lack of oxygen is a serious limit for aquatic animals
who really tend to be very limited in capabilities. The really agile
and active aquatic critters are the air breathers -- birds, reptiles
and mammals.
Marc
Just for your interest, gills do more than just extract oxygen.
Have a good look at the blog entry about how the gill evolved
after fish left the water.
http://scienceblogs.com/pharyngula/2006/06/deep_homologies_in_the_pharyng.php
(signed) marc
.
Windy
Inez wrote:
> Mark wrote:
> > Anyway; my understanding is that oxygen gets somehow extracted, gets in
> > the blood stream, is carried to viatl organs that need it (or organism
> > functions) that use it?
> >
> > So; the question is ; if the stupid shark can do it, why with all the
> > technical knowledge in engineering we can not build a machine that does
> > it and can be used instead of aqualung?
>
> Wikipedia is cool
>
> http://en.wikipedia.org/wiki/Like-A-Fish
That is interesting, I didn't know plans were that far. But it seems
like any sort of useful scuba diving alternative would still have to
include a rebreather, which sort of defeats the point.
Perhaps they should combine it with an underwater scooter, since it's
necessary to pump around large amounts of water anyway. Then the diver
would indeed be like a shark, needing to move constantly to get oxygen
:)
-- w.
r norman
Unfortunately that site suffers from a serious flaw right at the
start. It is true that gills are very important for salt balance,
both as part of the problem and as part of the solution. It is true
that land animals tend to have the opposite salt balance (osmotic)
problem than salt water fish. And it is true that the thyroid and
parathyroid glands are important in calcium regulation. However, they
really are not important in overall salt or osmotic balance because
calcium is such a small constituent of body fluids. So the
significance of the thyroid and parathyroid is totally separate from
the problem of salt and osmotic balance.
Windy
r norman wrote:
> On 5 Jul 2006 15:58:50 -0700, "Mark" <tent...@hotmail.com> wrote:
> >So; the question is ; if the stupid shark can do it, why with all the
> >technical knowledge in engineering we can not build a machine that does
> >it and can be used instead of aqualung?
>
> who really tend to be very limited in capabilities. The really agile
> and active aquatic critters are the air breathers -- birds, reptiles
> and mammals.
Some of those sharks and fish could fool me into thinking they can be
pretty active, as well...
-- w.
Desertphile
Never worry about "asking a stupid question:" the only stupid question
is the one not asked. Ignorance is the default.
Humans have already invented the "rebreather" that replaces the SCUBA
air tank; however, they are considered dangerous to use.
Mammals need a hell of a lot of oxygen (much more than fish, I assume);
I suspect any gill membrane that can supply a human being with enough
oxygen would be very large and bulky.
r norman
They do pretty well for short bursts of activity. You are also
thinking of a very tiny handful of very specialized species that tend
to catch our attention while the large numbers of sedentary or
slow-moving animals escape our notice. Still,, the whales and
dolphins and seals and the wide variety of aquatic birds have
enormous advantages with their high metabolic rates. That, of course,
is also associated with having high body temperatures, something very
difficult to do with gills. (Now, you are going to tell me about the
few again highly specialized fish that manage to keep at least
portions of their body warm.) Not only do gills tend to produce
massive losses of heat to the water, they also simply don't gather
enough oxygen to support really high metabolic rates.
Still, as you point out, there are always animals with extreme
adaptations to allow them to escape the usual rules. They pay for
this specialization in other ways, though.
Dick C
>
> All aquatic organisms have the ability to extract oxygen from the
> water in which they live. The simple fact, though, is that there is
> really only a very small about of oxygen dissolved in water. Sea
> water normally contains only about 5 to 10 ml of oxygen per liter.
> Air contains 210 ml of oxygen per liter.
I was curious about what that meant in real life. Google showed that the
average human has a lung capacity of about 5 liters. Which means that
a human would get 1050 ml of oxygen in their lungs. So, in order to get
the same amount of oxygen you would need 105 liters of water.
--
Dick #1349
"They that can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety."
~Benjamin Franklin
Home Page: dickcr.iwarp.com
email: dic...@comcast.net
CreateThis
The stupid shark didn't 'do it'. It was done by an evolutionary
process that's even more 'stupid' than the shark, but had the
advantage of millions of years to sift out countless mindless mistakes
and dead ends in the development of the gill. If all the world's
monkeys were typing on typewriters for all that time, one of them
probably would have written the scientific paper.
Too bad monkeys didn't invent the typewriter until after they invented
religion.
CT
r norman
wrote:
>r norman wrote in talk.origins
>
>>
>> All aquatic organisms have the ability to extract oxygen from the
>> water in which they live. The simple fact, though, is that there is
>> really only a very small about of oxygen dissolved in water. Sea
>> water normally contains only about 5 to 10 ml of oxygen per liter.
>> Air contains 210 ml of oxygen per liter.
>
>I was curious about what that meant in real life. Google showed that the
>average human has a lung capacity of about 5 liters. Which means that
>a human would get 1050 ml of oxygen in their lungs. So, in order to get
>the same amount of oxygen you would need 105 liters of water.
This is a nice attempt to show the problem. Unfortunately, it isn't
really the correct analysis. The lung capacity is not a true
indicator of how much material must flow through the body in a given
time -- it is rate, not volume that must be considered.
Probably the best measure is what is called the "ventilation to
perfusion ratio", the flow rate of water through the gills or air
through the lungs, the ventilation rate, compared to the flow rate of
blood through the body, the perfusion rate. Fish and humans have
similar hemoglobin and therefore similar abilities for the blood to
carry oxygen. If we were to try to take oxygen from the water, our
blood would still have to carry the oxygen to the body so that our
perfusion rate would not change. We air breathers usually have a
ventilation:perfusion ratio of about 1:1, humans pump about 5 liters
per second of blood through our heart and about 5 liters of air
through our lungs. There are differences between total ventilation
and functional or alveolar ventilation, but we will ignore those for
simplicity. On the other hand, fish tend to have about a 10:1
ventilation:perfusion ratio. So we would need to pump 50 liters of
water through our gill substitutes each minute to get the oxygen we
need. Since our metabolic rate consumes about 250 ml of oxygen per
minute, 50 liters of water with 5 ml oxygen per liter would handle
the job. Note: 50 liters of water is 50 kg. In American
non-standard units, that is a dozen gallons of water per minute or
well over 100 pounds.
Incidentally, in air breathing, although we do pass 5 or more liters
of air through our lungs each minute, a gas volume that contains more
than 1 liter of oxygen, we only remove about 250 ml of the oxygen so
that the exhaled air still has about 3/4 of the oxygen left. We are
extremely inefficient in our breathing. Fish (and birds) have far
more effective oxygen removal methods. So much for human perfection!
This remnant oxygen is one major reason why rebreathing systems can
work. If you remove the CO2 accumulation, you can rebreathe the same
volume of air a couple of times before the oxygen level drops too
much.
Bryan Heit
> 1. Lungs can already do this. The movie "The Abyss" has a short
> section of a mouse being immersed in a special liquid that allows
> oxygen exchange in the lungs, the mouse survives. My understanding is
> that this was not special effects, but actual footage. Google will
> find you a number of references.
This is correct. The product actually went into clinical trials for
preemie baby's, under the name "Liquivent". The product didn't work as
well as people had hoped, and there isn't much interest in it anymore.
There was hopes to use this for SCUBA diving, space flight and various
other uses. Unfortunately, the equipment and volume of liquivent
required to keep a person alive is quite massive, making it impractical
for most uses.
Wikipedia has a good section on this (search for "Liquivent" or "liquid
breathing")
> 3. What is wrong with the aqualung? it does the job well. Or to put it
> another way, why do you think there is a need to produce some other
> device to replace the aqualung?
As an avid diver I can tell you there is a lot wrong with conventional
SCUBA system. The easiest thing to point out is the limitations in
terms of bottom times. A standard SCUBA cylinder, which holds ~80 cu
ft of air, is fairly limiting. How long a tank lasts depends on a
variety of factors, including the diver and depth, but based on my own
usage these standard tanks are good for:
1) 1-1.5hrs at 10m/30'
2) 20-30 min at 25m/80'
3) 10-20 min at 40m/130'
Add to that the issue that SCUBA tanks are heavy, and carrying multiple
tanks is both difficult, and under some circumstances is dangerous.
Likewise, these gas cylinders present a potential danger; my first
SCUBA instructor was killed by a tank which exploded while it was being
filled.
Another issues which replacement technologies could potentially fix is
the bends. The bends (properly called DCS) is a result of too much gas
being absorbed by the divers blood. When they surface bubbles form in
the blood and tissues, potentially leading to death. Think of a bottle
of pop when you open it - under pressure it's fine, but release the
pressure (which occurs when a diver surfaces) and you get bubbles. An
apparatus which could limit the amount of gas absorbed into the blood
would be of huge benefit to divers.
Bryan
Iain
Mark wrote:
<snip>
Why do you assume that if the shark can do it it should be easy for us?
~Iain
Shane
> Shane wrote:
[...]
I did not word my question as well as I could have. As a recreational
SCUBA diver myself, I understand the problems and limitations of the
current system. However, it works well enough for the vast majority of
users, and other technologies are available for those that require
them, providing they can pay the extra costs. My point is that like
the internal combustion engine, the SCUBA system does the job for a
relatively modest cost, and while a better system is both possible and
desirable, there is no great driver for the change, yet.
guscubed
Windy wrote:
> Inez wrote:
> > Mark wrote:
> > > Anyway; my understanding is that oxygen gets somehow extracted, gets in
> > > the blood stream, is carried to viatl organs that need it (or organism
> > > functions) that use it?
> > >
> > > So; the question is ; if the stupid shark can do it, why with all the
> > > technical knowledge in engineering we can not build a machine that does
> > > it and can be used instead of aqualung?
> >
> > Wikipedia is cool
> >
> > http://en.wikipedia.org/wiki/Like-A-Fish
>
> That is interesting, I didn't know plans were that far. But it seems
> like any sort of useful scuba diving alternative would still have to
> include a rebreather, which sort of defeats the point.
You may be interested in the January 6th issue of New Scientist that
has a feature all about artificial gills, how they work and how
advanced the technology has got:
http://www.newscientisttech.com/channel/tech/mg18925331.300.html
"In the 1980s, Fuji Systems of Tokyo developed a series of prototype
gills for divers as a way of demonstrating just how good its membranes
are. The early versions resembled a small fridge strapped to a diver's
back, while the most advanced prototype, called the Donkey III,
consists of a coffin-shaped box that has to be pushed in front of the
diver. It's huge, but it does work. In a televised demonstration in
2002, it supported a diver in a swimming pool for 30 minutes."
The article in the magazine incuded a picture of a diver using the
'Donkey III' - it looked decidedly ungainly. The article aslow hs some
information about Bodner's like-a-fish device:
"Enter Israeli inventor Alon Bodner, who unveiled a novel approach last
year. Instead of a membrane gill, he plans to use an industrial process
for separating gases from a liquid, based on the principle that if you
lower the pressure of a liquid, for example with a centrifugal pump,
the gas dissolved in it bubbles out (see Diagram). Bodner claims his
battery-powered device will be able to extract virtually all the air
dissolved in water. With seawater, this would typically yield a gas
containing 34 per cent oxygen. Crucially, because Bodner's device
extracts nitrogen as well as oxygen from the water, nitrogen loss is
not an issue.
But there is a problem with this approach. The system would have to
process more than 1000 litres of water per minute just to provide
enough air for a diver to breathe at the surface. Descend 10 metres and
the pressure doubles, so you need to extract twice as much air to
provide the same volume. Go deeper and you need to extract even more.
The only way to make the system practical is to make it part of a
rebreather."
Stephan Schulz
Bryan Heit wrote:
>
>Another issues which replacement technologies could potentially fix is
>the bends. The bends (properly called DCS) is a result of too much gas
>being absorbed by the divers blood. When they surface bubbles form in
>the blood and tissues, potentially leading to death. Think of a bottle
>of pop when you open it - under pressure it's fine, but release the
>pressure (which occurs when a diver surfaces) and you get bubbles. An
>apparatus which could limit the amount of gas absorbed into the blood
>would be of huge benefit to divers.
Nothing that allows you to breathe a gas mixture under pressure is
going to completely overcome this problem - if you use to much Oxygen
in the mixture, you get Oxygen overexposure. If you use inert filler
gases, they will get disolved into your blood stream. And using a
non-inert gas has obvious other problems ;-)
That said, going to dive without a 30 lb tank would be a pleasure,
even if it does not increase bottom time.
Stephan
--
-------------------------- It can be done! ---------------------------------
Please email me as sch...@eprover.org (Stephan Schulz)
----------------------------------------------------------------------------
Mark
the original one.
here is the link:
Dick C
A couple of things about this. First of all, this is the usenet. The usenet
does not exist on any single server, it is all over the internet, and
google
groups is just one of many ways to read the usenet. Posting a link to
google
groups like that is of no use to most people. Google has one advantage and
that is that they archive the usenet back to the beginning of it.
Secondly, since this is not a bulletin board you do not need to post a link
to a new thread, you do not even need to tell us you are starting a new
thread. But it is nice that you do it, just give the title of the thread.
J. J. Lodder
> I have a question. Probably the answer is very simple, it is just
> because I am from the school long time ago, I have forgot the answer.
>
> Anyway; here is the question. The fish, e.g. the shark, that exists
> already for millions years if not more, has the ability to extract
> oxygen from water? Is that a correct statement? It is possible I make a
> wrong assumption so the rest of my questions dont even apply.
The shark does not extract anything.
The oxygen comes of it's own accord,
by diffusing from a higher concentration to a lower one.
With a corresponding entropy increase of course,
Jan
Mike Painter
>
> As an avid diver I can tell you there is a lot wrong with conventional
> SCUBA system. The easiest thing to point out is the limitations in
> terms of bottom times. A standard SCUBA cylinder, which holds ~80 cu
> ft of air, is fairly limiting.
The standard aluminium tank used in diving today in the US is "named" an 80
but only holds 77.4 if filled to legal capacity.(3000 psig) It is fairly
common to overfill the tank.
<snip>
>
> Add to that the issue that SCUBA tanks are heavy, and carrying
> multiple tanks is both difficult, and under some circumstances is
> dangerous. Likewise, these gas cylinders present a potential danger;
> my first SCUBA instructor was killed by a tank which exploded while
> it was being filled.
Tanks are heavy and awkward, especially in the USA where DOT did not allow
the Divator system in.
Today NASA uses then for both SCBA (the original use) and SCUBA.
Sad that the Divator(which I got to dive with once in 1974) in steel still
weighs less and holds more air and is far more comfortable to wear in and
out of the watere than any SCUBA gear and the vast majority of SCBA gear.
Only the latest 4500 PSIG fiber tanks are lighter, but they hold less and
are still chubby.
>
> Another issues which replacement technologies could potentially fix is
> the bends. The bends (properly called DCS) is a result of too much
> gas being absorbed by the divers blood. When they surface bubbles
> form in the blood and tissues, potentially leading to death. Think
> of a bottle of pop when you open it - under pressure it's fine, but
> release the pressure (which occurs when a diver surfaces) and you get
> bubbles. An apparatus which could limit the amount of gas absorbed
> into the blood would be of huge benefit to divers.
>
> Bryan
That should read "limit the amount of Nitrogen absorbed by the blood" as
that is the gas that causes problems.
There are other huge problems caused by breathing with lungs rather than
gills.
Most important is that oxygen at higher partial pressures than we normally
breath is toxic. Long time use at even low pressure is a problem.
For the diver pure O2 will cause convulsions and death with little or no
warning starting at a depth as little as 25 feet depending on the diver. At
33 feet (two atmospheres, 29.4 psia) it's pretty much guaranteed in a short
time. Jacques Cousteau survived two such incidents in the early days. They
thought the problem was caused by bad O2 the first time.