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Name: Bill
Status: other
Grade: other
Location: ID
Country: N/A
Date: April 2006
Question:
Osmosis occures when you soak your hand in freshwater, meaning that the water passes through pores or membranes in your skin, whatever they may be, to accumulate more water in your cells, thus making them swell, and your skin begins to wrinkle, right? But what happens if you were to soak your hand in salt water?


Replies:
Bill,

First off, your original statement that osmosis occurs between your skin cells and fresh water isn't correct and cannot be correct. Here is why: Osmosis is the transport of water across a semi-permeable membrane, which always flows across the membrane from the lower salt concentration to the higher salt concentration. Fresh water has a much lower salt concentration than your body so the process of wrinkling cannot be explained via osmosis.

So why does your skin wrinkle in fresh water, and what would happen in salt water? To start, you have a dead layer of skin cells layering your entire body. This layer is thicker in some places (like your palms, soles of your feet) and thinner in others. This layer of dead skin cells is heavily keratinized. Keratin is a fiborous, insoluble protein that is not only found in your dead skin layer, but is the major component in your hair, nails and horns (if you have them ;). The keratinized skin layer helps drastically reduce water intake and excretment and is one of the major evolutionary advances of vertabrates.

So, how does all this relate to wrinkled skin? The keratin-filled dead cell layer will imbibe water via capillary action--not osmosis. When this occurs, the cells will swell and take up a greater volume and surface area. It is the swelling that causes the wrinkling. In salt water, simple diffusion would occur and your skin will get tight due to the water in your dead cells diffusing into the salty water (via simple diffusion, not osmosis).

Matt Voss

Water travels from areas of lowest salt conc. to highest salt conc. so regardless what type of water your in, if the water is saltier than your skin, it will draw water out of your skin. If it is less, you will actually absorb some water!

Grace Fields


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