SUBJECT: What causes wrinkled fingers?
DATE: 9/96
Soon I'll be covering osmosis in my introductory biology class. I suspect
that osmosis plays
a role in the wrinkled fingers and toes we get while soaking in the tub.
Can anyone
out there give me the details on how this wrinkling occurs? It would add
a little spice to
my lecture.
Thanks,
Janet R. Mihuc, D.A.
Biology Program
Louisiana State University
Baton Rouge, LA 70803-5615
504-388-8785
504-388-8239
jmihuc@unix1.sncc.lsu.edu
As far as I know, wrinkled fingers result because the keratin-laden
cornified epithelium on our hands and feet takes up water; the swollen
keratin causes the wrinkling. You'll notice that skin on other parts of
our bodies, which is thinner and doesn't have nearly as think a stratum
corneum (the dead layer that is mostly keratin), doesn't wrinkle. The
stratum corneum is by far the thickest on palms and soles because the
keratin is needed in places where the epidermis gets the most wear.
Sara Hiebert
Biology Department
Swarthmore College
Swarthmore PA 19081
I was glad to read Sara Hiebert's explanation because I found a puzzling
one
in "Why Doesn't My Funnybone Make Me Laugh?" by Alan Xenakis.
He says that
when the soap and water wash off the oils, the skin cells are exposed to
water. I follow that part ok. Then he says that water begins to leak out
of
the skin cells, adding "These cells have semipermeable membranes in
their
walls. This means that they can give up water but they can't take it in
as
easily." How could that be?
Jean Dickey
I'll go out on the limb: Xenakis' explanation sounds a bit like
pseudo-scientific gobbledy gook -- it sure doesn't sound logical to me:
Even if the oils washed off the surface of the skin (and even if there
weren't the cornified layer of dead and dying cells!) one would expect the
"fresh" water of the bath would be hypotonic to cell protoplasm
and diffuse
straight in the knockout!!
Debbie
Deborah M. Langsam
dmlangsa@email.uncc.edu
Department of Biology
UNC Charlotte
Charlotte, NC 28223
Phone: 704-547-4054
FAX: 704-547-3128
Sounds to me like someone doesn't quite have it right. The walls and the
water going from cells to a hypotonic solution make this explanation
unlikely, wouldn't you say?
Jean Desaix <jdesaix@email.unc.edu>
Probably Alan Xenakis was confusing "can" with "does."
If the cells have
semipermeable membranes the water can move in either direction, but if your
foot is in the bathtub (and you haven't added large amounts of epsom
salts), net movement of water will be out of the cells to the solution of
lower osmolality. Still, I don't know that this really explains the
wrinkling.
Sara Hiebert
Biology Department
Swarthmore College
Swarthmore, PA 19081
610-328-8053
Xenakis is an M.D. so he learned about osmosis in his Introductory Biology
course somewhere...or maybe biology in med school is different. What's (also)
weird is that he prefaced this explanation with a paragraph about how we
must
wonder why anything else such as sponges and paper towels will take up water
while skin shrivels "like a prune." (Maybe because it doesn't...?)
Sara's explanation also explains why wrinkled skin softens. If the skin
were
actually losing water it seems like it would feel dehydrated, too.
So can we test this with the old weigh-before-and-after technique? Any ideas
for where we can get simulated severed fingers? ; )
Jean Dickey
I have a suggestion:
Water will enter your body in a freshwater bath/swimming pool/lake (not
necessarily through skin...also through mucus membranes). Your now-fatter
body
is stretching the skin. The skin can't stretch evenly because it isn't free
but
attached at various locations. Consider stretching a piece of fabric: although
you are pulling it to make it larger, it still wrinkles where it is attached
to
your hands.
Look at the "wrinkles" your get while in the bath, they aren't
the same as the
wrinkles that appear when you are dehydrated [or old :)]. Those wrinkles
are not
the result of stretching.
Christine Case
Skyline College
case@smcccd.cc.ca.us
I just read Jean's note about using the weigh-before-and-after technique.
How
about the osmoregulation technique: compare the volume of urine excreted
after
swimming in fresh water for ____ min with the urine volume after swimming
in the
ocean for ___ min.
(The volume of urine in a swimming pool is probably high because the water
is
hypotonic to the humans.)
Chris Case
Water will enter your body in a freshwater bath/swimming pool/lake
(not necessarily through skin...also through mucus membranes). Your
now-fatter body is stretching the skin. The skin can't stretch
evenly because it isn't free but attached at various locations.
Consider stretching a piece of fabric: although you are pulling it
to make it larger, it still wrinkles where it is attached to your
hands. >>>>
I don't buy it. First of all, the phenomenon doesn't depend on
exposing mucus membranes to water- your fingers get wrinkled even if
you only soak your hand. Secondly, if water could enter the body that
easily, it could also leave, and dry air has an extemely low water
potential. If I recall my vertebrate evolution correctly, the big
advance leading to terrestrial verts was heavily keratinized skin so
the air wouldn't dry out our bodies (as it does to earthworms and
many amphibians, animals that do give responses like you describe.)
Sara Hiebert's explanation still sounds good to me.
John Dickerman
Northern Illinois University
Hi, labbers:
I could've sworn I read in a text somewhere that, when a hand is submerged
in fresh water, salts diffuse out and water follows osmotically. By the
same token, skin is supposed to feel "tight" after submersion
in salt water.
I'll check a bunch of books tomorrow, if I have time!
Best,
Kerry Kilburn
ODU Biological Sciences
No matter how you slice it, there's no way water could flow OUT of
our bodies/skin into FRESH WATER by OSMOSIS. We're pretty salty
[saline = 0.3 OsM]; if we were freely permeable to the water in the tub,
we'd have to accumulate water. If we excreted enough salt in the tub to
raise the concentration of salt above that of our bodies, all we'd have
to
do to cure high blood pressure would be to take a bath, and all our salt
would be sucked right out of our bodies!!
And... if the soap removed all of the protection/waterproofing of our
skin, we'd be in major trouble. Not only would water be able to flow
[probably IN, not OUT], but our living tissue would be exposed to the
SOAP as well. And I imagine soap would lyse those cells fairly rapidly,
by solubilizing our membranes, yes?
... but then again, I'm "just" a geneticist; could I be missing
some
major physiological fact here??
-Bob Moss
Wofford College
MOSSRE@WOFFORD.EDU
Our skin is not water permeable. If it were we would quickly dehydrate in
the hot sun. We do not absorb water while swimming either. The wrinkles
must be the result of water attaching to the keritin or other substance
in
the epidermis causing it to swell. Yes salt water does make your skin feel
tight (I spend many hours changing the water in marine aquaria). This is
probably due to the salt water removing water from the keritin.
Paul Quiggle
pquiggle@cruzio.com
>From what I read several years ago in one of those short "Why does
it do
that" sorts of columns in ? Discover? Science 8_??? Health??, skin
cells
take in water along the concentration gradient, just as one would
expect. However, the underlying connective tissue does not swell, and
thus puckering occurs. Yes, you hear an echo. This was suggested
previously in similar words.
***************************************************************
Louise Baxter email: baxterl@cwu.edu
Department of Biological Sciences phone: 509-963-2745
Central Washington University fax: 509-963-2730
Ellensburg, WA 98926
About prune fingers:
The dead layer of keratinized skin cells (which comprise the stratum corneum
of the skin's epidermis) serve as a moisture barrier, both in and out. It
doesn't make sense for living skin cells (which are under this keratinized
dead cell layer) to take up water. An animal wouldn't likely be constructed
this way, although Christine Case (I love her microbiology text!) is correct
about the possibility of uptake through the moist, mucous membranes
(non-keratinized, stratified squamous epithelial membranes lining the mouth,
esophagus, anus and vagina). Water can also be taken in by the simple (one
layer) epithelial sheets lining the digestive tube. However, this would
result in a simple case of edema which, to the best of my knowledge and
experience, has little effect on the appearance of the skin. If anything
it
would stretch the skin like an expanding balloon. The stretching forces
would
be applied evenly from below--no wrinkles.
What actually happens in the tub or pool is that the dead, keratin-filled
cells imbibe the water (just like soaked beans or paper towels) because
of
capillary action and swell (definitely not osmosis, which, as a form of
diffusion, is powered by thermal energy, not the cohesive forces of the
water
molecules). This causes the stratum corneum to occupy a greater surface
area.
Because it is attached thoroughly to the tissues below (and they have not
changed), it must wrinkle to account for the greater surface area. The
stratum corneum on the palms and soles is much thicker than that on other
parts of the body and so imbibes lots more water and makes the wrinkling
more
evident. When you see your fingers and toes wrinkle up after long exposure
to
water rest assured that the skin is just doing its job of intercepting water
that would otherwise invade your body by an inappropriate route.
I'm not sure about salt water but what Paul Quiggle says (that it removes
existing moisture form the stratum corneum) sounds plausible. I would think
that a tug-of-war would be going on between the cohesive forces of the water
molecules and the tendency for the stratum corneum-held water to exit (by
simple diffusion) into the surrounding salt water. Seems like the keratinized
cells would first have to become more hydrated than usual before this could
take effect. Not sure.
Dave Williams
ProfDHW@aol.com
I have read that an absence of the wrinkling response has been observed
in limbs that are neurologically impaired (perhaps spinal cord injury).
Can anyone veryify or explain this?
Peter Ommundsen
Selkirk College
This sounds like a great project for students in general bio up
through biomicrosopy. Without going into great detail, have students:
1. section off a piece of the outer layer of skin (stratum corneum)
2. stick it under a microscope and record results
3. soak it in water +/- soap
4. stick it under a microscope and look at cell size and structure
5. compare results
Permutations of the above experiment
1. skin from fingers vs palm, palm vs. surface of extremity, skin that
flakes off from a sunburn
2. attempt to weigh the skin before and after to see if has become
hydrated, if so how much water did it absorb, what is the skin wieght to
water ratio.
3. take a piece of skin weigh it and let it sit in the sun for a couple
of days, how much water was lost.
Although the experiments listed above are may not be an exact measurment
of
whats going on and certainly more detailed methods are required, they
would be a great opportunity for exploratory science for all students.
The very disccussion that has been going on via biolab, could be taking
place in the lab. I'd bet the students would love the chance to solve a
problem like this one. The discussion topics are endless. osmolarity,
hypotonicity, semi-permeable membranes, diffusion, osmosis.
A year ago in our physiology lab course, a student wanted to know what
shampoo's did to increase the thickness of hair. The shampoo was named
"Thicker fuller hair in 12 washes." The student took hair samples
from
18 individuals, took micrographs of several sections of the hair
(follicle, middle and end) then washed the hair 12 times,
6 with water
6 with regular shampoo
6 with super thickening shampoo
then reshot the pictures and compared the results.
In addition, she gave shampoo samples to individuals to try for
"qualitative results". I don't know if I believe the results (the
super
shampoo increased hair thickness by 10-12%), but the student learned alot
of science and had fun doing it.
Terry Favero, Ph.D.
Biology
University of Portland
5000 N. Willamette Blvd.
Portland, OR 97203
email: favero@uofport.edu
(503) 283 7373