Well, as a [former] anatomy & physiology professor, I'm going to disagree with your former professors (or alternatively, your memory of the courses).
B Brian wrote:
While it is true water will not penetrate the skin (for the exact reasons you stated) the outermost layers absolutely do absorb water. This is why your hands get wrinkly after a long bath. Because the absorbed water causes the skin to expand. The rest of your skin is the same way. In fact, water will slowly get absorbed and released with even minor changes in humidity. When it does get absorbed, the lower living layers of your skin become more hydrated (because all of our living cells constantly need water). This in turn required less water from withing the body, and also slows down your body's natural sweating (again the small amount we don't normally notice). Hence you loose less water overall which then kicks in you urine production to keep things balanced.
Again, no. The wrinkling of the skin you speak of only occurs when you are truely soaked, and only for a significant period of time. It is thought (by most), to be a response caused by absorption of water into the keratinocytes (which seems born out histological preparations), but the effect is transient, and there is no evidence that water is resorbed into the blood stream, rather it simply evaporates again. I would also be remiss not to mention that recent research appears to demonstrate that the wrinking response requires live nerve cells, in the dermis, to activate. This suggests it's actually a reflexive response, driven by tiny bundles of smooth muscle embedded in the skin. Those researchers suggested it might actually represent a adaptation to provide more surface area, and therefore grip, when your skin is wet, and therefore slippery.
However this isn't really relevant to the discussion, as the topic was why people experience more urgency, or wetting, when cold and/or clammy or, and not what the effects of long term saturation are.
B Brian wrote:
And the cold cutting off circulation is what happens in moderate to extreme cold and is normally called hypothermia. In low cold situations (like stepping into the ac or grabbing a bag of ice on a hot day) your body absolutely does take advantage of this cooling to keep you core body in temp (no sweating needed). It does this by increasing the blood pressure and by dilating certain blood vessels which lead to the skin. This increased circulation also has the side effect of producing more urine as I mentioned.
You've got this bit precisely backward. In mild to moderate cold, your body does what I previously described. You constrict external blood vessels, conserving warm blood in the core. This drives up blood pressure, causing increased preload in the heart, and triggering baroreceptors in the aortic arch to inhibit sinoatrial stimulation, thereby decreasing heart rate, and normalizing BP.
In moderate to severe cold (hypothermic conditions) the body's ability to thermoregulate begins to break down. The heart begins to race, people begin to sweat, and production of vasopressin (anti diuretic hormone) ceases. Though, again, hypothermia isn't pertinent, as people complaining of a cold/clammy day are typically just uncomfortable, not hypothermic.
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