simple diffusion and skin cells

[Biology teacher]

Hi

I wonder why can't skin cells or eye cells take oxygen directly from the surrounding air by simple diffusion ?

[kotoreru]

I could be wrong, but I believe skin cells do permit gas diffusion to a point. This is why painting someone's body entirely in paint is a really bad idea.

As for the eye, well the sclera is a thick layer of protein (isnt it?) so its not cells that are obstructing gas.

[James]

When amniotes evolved keratinized skin to avoid dessication the ability to do cutaneous exchange was hindered and almost completely lost. The skin is too thick, and pretty much impermiable.

[xand_3r]

About 1% of respiration occurs through skin. This is an extremely low value if you take in consideration that the skin is almost always in contact with air and it has a very large surface. Skin is impermeable to water and solutes but liposoluble substances (including gases) can pass.

[Tae Jun, Yoon]

Well, as you know diffusion of gas like oxygen occurs through phospholipid in cell membrane. As I know, most of membrane of skin cell doesn't contact with outer environment - They are protected by protein. I think Oxygen can't penetrate the protein.

[Darby]

As I understand it, the surface cells can take in enough oxygen from the air to keep themselves alive (they are quite a distance from their blood vessels); skin cells die as they dehydrate, but corneal cells have blinking and the aqueous humour to keep them hydrated (but how they stay nourished I'm not sure).