I have been looking all day, reading so much and this explanation does make sense. We still need to find out if the wrinkling stays or not, I would say it would smooth out as the skin dries..makes sense to me. blue
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://www.madsci.org/posts/archives/2004-07/1090270850.An.r.htmlDate: Sat Jul 17 11:56:27 2004
Posted By: Dave Williams, Science Department Chair, Valencia Community College
Area of science: Anatomy
ID: 1089738260.An Message:
Karen:
Unfortunately you have been badly misled by the previous answer
that you have seen on Mad Sci. Young Mr. Carlson is under the
misapprehension that osmosis moves water into the human body.
While nothing could be farther from the truth, this is a common
mistake among new biologists (or old ones who don't think).
One of the main purposes of the skin is as a water barrier. It keeps
water in and out of the human body.
Water moves into the dead layer of flattened skin cells that make up
the stratum corneum of the skin (the keratin that Mr Carlson referred
to) by capillary action, the same way it soaks into a paper towel. No
doubt it first seeps into the spaces between the flakes of dead skin.
Then the dead skin cells become rehydrated and the layer swells
and becomes more expansive, thereby increasing it's surface area.
But... the stratum corneum is attached to the underlying layers of
living skin cells in the epidermis which are in turn attached to
connective tissue in the dermis. In order to accommodate its new
surface area the stratum corneum must wrinkle. It is able to do so
because the tissues to which it is bound are somewhat elastic and
stretch to accommodate the larger surface. The resulting interaction
between the swollen dead skin layer and the underlying, slightly
elastic tissues to which is its connected produces the corrugated
appearance which we sometimes call "prune fingers".
Some biology instructors may not be prepared to accept this
explanation. It is a sad fact of modern science education that many
teachers (even university professors who do very advanced research)
do not question their initial, simplistic explanations for ordinary
phenomena outside their area of expertise. The prevailing notion
among biology teachers that osmosis accounts for ALL water
movement is as rampant, in my experience, as is the popular but
unfounded notion that we use only 10% of our brain.
To the best of my limited knowledge, water (on Earth, at least) moves
in response to four different forces.
1. It responds to gravity, as when water is poured from one container
into another. This is called "bulk flow" of water. It is responsible for
the often observed phenomenon that "water seeks its own level".
2. Water will also respond to pressure, as when it is pumped from
one location to another. Such pressure is called "hydrostatic
pressure" and is also responsible for some biological water
movement, as when water is lost from capillary blood vessels near
the arterial (pressurized) end.
3. Water will move as a result of electrostatic intermolecular forces;
the repulsion and attraction generated by partial charges on the
surface of the water molecule. A common type of this movement is
called "capillary action". This is the movement of water up the sides
of tubes in apparent defiance of gravity or into small spaces of all
kinds. This type of water movement is responsible for the fact that
water from a puddle on a table will soak into our misplaced shirt
sleeve. Also, it contributes in no small way to the movement of water
up the stems (trunks) of large trees.
4. Osmosis is, like its parent concept diffusion, powered by the
thermal energy inherent in the system of which the water is a part
(reflected in the temperature of the surroundings). Osmosis is the
diffusion of water molecules through a semipermeable membrane. A
semipermeable membrane is a thin membrane that will let water
molecules through but will hold back large solute molecules
dissolved in the water. Such a membrane must separate two water
compartments in order to facilitate the diffusion of water.
In each of the four examples the same explanatory motif can be
invoked: water moves from where it is in greater concentration to
where it is in lesser concentration. We pour water from a full jug into
an empty glass. We pump water from the well into the empty sink.
Water moves from the puddle on the counter top to the many, small
empty spaces in the paper towel. Water moves from a solution with a
lower concentration of solutes (where the water is in higher
concentration) to a solution with a higher concentration of solutes
(where the water is in lower concentration). The slipshod definition of
diffusion as "the movement of a substance from higher to lower
concentrations", when applied to osmosis, leads to much confusion
stemming from the reverse nature of the relationship between the
water concentration and that of the solutes.
What is most often missing in the typical presentation of osmosis is
an explanation of the energy source. Typically, students walk away
from a lecture on osmosis with the idea that it requires no energy --
that it is energy free!
This, of course, is not the case. Osmosis (like diffusion) depends on
thermal energy which is manifested in the incessant motion of the
molecules. The point that many instructors are trying to make
(perhaps without much reflection given to it) is that no energy needs
to be supplied. It is already present in the system. Unfortunately, this
is usually carelessly conveyed as "no energy is required for
osmosis".
The notion that osmosis has any potential (at least on the short term)
to affect an immersed living human body completely covered by a
relatively thick layer of dead cells, which does not constitute a
semipermeable membrane separating two water compartments, is
suspect. The fact that even extended immersion seems to have no
effect on the actual water balance of a living human body needs
some sort of explanation, no doubt.
A thick yet porous membrane may, given extended time of immersion
in fresh water (perhaps much longer than a typical bath), emulate a
semipermeable membrane. Of this and its results I am not sure. I
am sure that the "prune fingers" effect cannot be attributed to
osmosis.
The $64 question, for those inclined to tackle it, is: "Why does the
wrinkled effect only appear on the skin of the finger tips (or toe tips)
and not on the palms (or soles) and other parts of the skin?"
Mr. Carlson's explanation does not hold water (Just a little joke!) for
the reasons I have given. The answer, I think, lies in the fact that the
stratum corneum on the palms and soles is so thick that we don't
notice the (large) wrinkles and that on other parts of the body is so
thin it can't pull effectively against it's connection with the dermis; it
can't stretch the elastic, so to speak. Bear in mind, however, that my
answer is just an educated guess (just like Mr. Carlson's). I may be
wrong.
In fact, there is another hypothesis. Quite frankly, I don't buy it but it is
worth considering. The idea is that water does actually get into your
body when you soak and the the wrinkling response is from nerve
activity attempting to keep the water out. Here is a news release
about this idea:
http://www.hindustantimes.com/news/181_827772,00500011.htmI have not found an original source for this study so am reserving my
judgment. My main source of skepticism about the study is the
statement:
"The test is based on the fact that water seeps in easily through the
pores in the hand, diluting the body's own liquids and changing the
electrolyte values."
This statement, as any professor of human anatomy and physiology
will tell you, does not have the ring of truth. If "water seeps in easily"
then it would be dangerous to get into the water. What "pores" are
they referring to? If a slight dilution of the body's own liquids is what
produces this effect, then why don't our fingers get wrinkled whenever
we become edematous (have excess water in our systems)?
Don't get me wrong, I am willing to admit and accept that there are
reasonable answers to these questions but we must have them
before we can rest with this hypothesis.
I hope that my answer has cleared up this question for you without
undue confusion. Science is like that. There are few pat answers.
Most everything is in the 'this-is-the-best-we-can-do-just-now' stage.
Here are some sources that agree with me:
I sort-of got the last word in on this one!
http://biowww.clemson.edu/biolab/wrinkle.htmlThis one references the previous discussion (which comes up easily
on Google) but cites someone else who agrees.
http://www.islandscene.com/body_knowledge/1999/990707/fingers/This next one is purported to come from the Library of Congress.
http://www.loc.gov/rr/scitech/mysteries/wrinkles.htmlHere is a good one.
http://www.seed.slb.com/en/watch/bathroom/fingers.htmC. Susan Brown, Ph.D. agrees with me.
http://www.birch.net/~lindabrown/000150.htmHere is another one of Mr. Carlson's answers. He has (quite
admirably) done some experiments but still has to explain away facts
(my fingers wrinkle in the ocean). Further, his answer is based on the
assumption the the human body interacts osmotically with it's
environment, an assumption which I do no accept.
http://www.madsci.org/posts/archives/feb99/917326845.Gb.r.html