Swimming
on a hot summer’s
day i s no doubt a ref resh i ng act i v it y. Af ter
soaking in the water for half an hour, however,
you might notice that the tips of your fingers and
toes become shrivelled and wrinkled, much like
a prune. Long showers and baths seem to invite
a similar occurrence. Why do we get ‘pruney’
fingers after lengthy exposure to water and what
biological purpose does it serve?
A previous school of thought suggested that
the main cause of skin wrinkling on fingers and
toes was the result of ‘osmotic swelling’ of the
outermost layer of skin (also known as the stratum
corneum). As the name suggests, this is where
water moves from a low solute concentration to
a high solute concentration through the wall of a
living cell. On the contrary, evidence suggests that
wrinkling does not occur in the denervated areas
of the digits
[1-2]
. A similar result is observed when
nerves are severed
[3]
.
Current studies have suggested that finger-
wrinkling caused by cold moisture exposure is due
to digit pulp vasoconstriction, or the narrowing
of the blood vessels. This mechanism is controlled
by the autonomic nervous system, part of the
peripheral nervous system that is responsible for
the control of important functions such as heart
rate, digestion and respiration. As a result, the
fingertip sees a reduction in volume, leading to
the ridge-shaped patterns on the tips of fingers
and toes
[3]
. However, finger-wrinkling still ensues
in warm water when vasoconstriction does not
occur. Moreover, what is the biological purpose of
this mysterious mechanism?
fingers
wrinkle
in
MOISTURE
By Oi Ying Wong
黃靄盈
為什麼手指
浸水後
會皺?
Why
DO
