how does epidermis get oxygen when there are no blood vessels?

usafmedic45 said:
Actually, it doesn't "off-load into the plasma" of the blood.
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It's messy if you can't build a mental model. It does off load into the plasma, or else it wouldn't be able to reach the cells since the RBCs don't leave the blood vessel under normal conditions. So you're going to have an oxygen concentration gradient of low PO2 in the interstitial fluid and a high PO2 in the capillary (where the diffused oxygen can constantly be resupplied by the oxygen bound to the RBCs). Thus, oxygen is going to diffuse down the gradient from the RBC to the plasma, to the interstitial fluid, where it can diffuse across the cell membrane into the cell, where it can be used in the electron transport chain.
 
JPINFV said:
It's messy if you can't build a mental model. It does off load into the plasma, or else it wouldn't be able to reach the cells since the RBCs don't leave the blood vessel under normal conditions. So you're going to have an oxygen concentration gradient of low PO2 in the interstitial fluid and a high PO2 in the capillary (where the diffused oxygen can constantly be resupplied by the oxygen bound to the RBCs). Thus, oxygen is going to diffuse down the gradient from the RBC to the plasma, to the interstitial fluid, where it can diffuse across the cell membrane into the cell, where it can be used in the electron transport chain.
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Thanks for the clarification. I knew it off loaded but I thought it just offloaded into the interstitial fluid and not the plasma itself (although they are the same thing due to the diffusion of plasma into tissues).....that's what I get for not staying up to full speed on my cellular physiology. LOL
 
I'm really really good at developing mental models.

If the RBCs stay in the blood vessel, how would the oxygen get from the the RBCs to the interstitial fluid if it doesn't initially diffuse into the plasma?
 
Enzyme wise could you be thinking 2,3DPG possibly?
 
I'm thinking more of physical location. The oxygen is bound to hemoglobin in the RBC. How does it physicially move out of the RBC, and ultimately out of the blood vessel if the RBC can't follow out of the blood vessel?
 
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