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



## phillybadboy (Dec 6, 2011)

how does epidermis get oXygen when there no blood vesSels running through it? also if you get a cut to the epidermis but no deeper than the epidermis would the scab turn dark or black or just stay yellow?


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## JPINFV (Dec 6, 2011)

The epidermis is comprised of dead cells. It doesn't need blood vessels. Ever scrape yourself and all you get is a white jaggedity line? There, you've cut your epidermis. If it bleeds, then you damaged the dermis.

Look up "stratified squamous keratinizing epithelium" (i.e. multiple layers of flat cells covered by layers of dead cells).


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## mycrofft (Dec 6, 2011)

*Says so right here on the box:"Diffusion from dermis"*

 http://en.wikipedia.org/wiki/Epidermis_(skin) The stratum corneum is dead cells, but some other cells are still alive.; there is not a defined barrier that says "this side is dermis, this side is epidermis", like the lining of an organ or whatnot, there is some graduation. Since simple chemical diffusion is more readily affected by pressure than circulation, this makes epidermal skin more prone to damage from blunt pressure; also, the skin, being adapted to not requiring lots of fresh circulation, does not die as fast as many other cells in the body, resisting such damage. Also why it dries out so fast sometimes.


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## phillybadboy (Dec 6, 2011)

so some cells of the epidermis is alive? if so how does it recieve oxygen? i know it can get some nutrients by diffusion, but how does it get oxygen if red blood cells can't diffuse leave the blood vessels?


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## usafmedic45 (Dec 6, 2011)

*rubs temple*


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## STXmedic (Dec 6, 2011)

phillybadboy said:


> so some cells of the epidermis is alive? if so how does it recieve oxygen? i know it can get some nutrients by diffusion, but how does it get oxygen if red blood cells can't diffuse leave the blood vessels?





JPINFV said:


> The epidermis is comprised of dead cells. It doesn't need blood vessels.


...


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## mycrofft (Dec 6, 2011)

*See, see:*





The lowest layer, the basal layer, continually produces cells which push their predecessors to the surface. The basal cells are very active, being thereby susceptible to radiation (including sunburn) and to carcinoma. If this process is disrupted through an autoimmune error,and the cell division goes haywire, you get some forms of psoriasis.


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## mycrofft (Dec 6, 2011)

*See, see:*





The lowest layer, the basal layer, continually produces cells which push their predecessors to the surface. The basal cells are very active, being the susceptible to radiation (including sunburn) and to carcinoma. If this process is disrupted through an autoimmune error,and the cell division goes haywire, you get some forms of psoriasis.


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## JPINFV (Dec 6, 2011)

mycrofft said:


>




...but the vast majority are either dead or in the process of becoming so.


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## phillybadboy (Dec 7, 2011)

mycroft, the layers requiring nutrients and oxygen are stratum basale,strtum spinosum,stratum granulosum, and stratum lucidum right? like the show too


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## mycrofft (Dec 7, 2011)

*I suppose. Basale for sure.*

Again, Nature rarely draws distinct lines of structure and function except where one organ bumps up agains other stuff...otherwise it would be a region not an organ. If you doubt that, go in after a "simple lipoma" and find yourself three inches deep, blood filling your cavity, and the stupid thing is still leading you further down into the darkness.


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## phillybadboy (Dec 7, 2011)

i guess my real question is how the cell groups without blood vessels recieve oxygen when red blood cells are too big to leak out of blood vessels, does hemoglobin or oxygen diffuse out?


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## Anjel (Dec 7, 2011)

phillybadboy said:


> i guess my real question is how the cell groups without blood vessels recieve oxygen when red blood cells are too big to leak out of blood vessels, does hemoglobin or oxygen diffuse out?



Capillaries are how they get oxygen. It allows 1cell through at a time. 

I cant use.the.big words or give exact reasoning, but what veins.and arteries dont do, capillaries do. 

The epidermis is dead cells, like hair and finger nails. 

The dermis has capillaries.


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## usafmedic45 (Dec 7, 2011)

phillybadboy said:


> i guess my real question is how the cell groups without blood vessels recieve oxygen when red blood cells are too big to leak out of blood vessels, does hemoglobin or oxygen diffuse out?


*facepalm*  Yes there is something of a mild oxygen diffusion gradient. It's a_ very_ low degree of diffusion because skin does not require a large amount of oxygen at all which is why you can place a tourniquet on a limb for several hours to a day and have no significant complications (and even when they do it's normally the muscles that are the source of the problem and not the skin).   No hemoglobin does not "leak out" because they would require the erythrocytes (red blood cells) to rupture.  This is called hemolysis and is a bad thing if it occurs with any regularity.  

I find your lack of basic knowledge disturbing.


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## STXmedic (Dec 7, 2011)

You forgot your disclaimer...


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## usafmedic45 (Dec 7, 2011)

Oops....sorry about that. LOL


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## usalsfyre (Dec 7, 2011)

Something not well covered in Basic class (or for that matter, some medic classes) is that O2 does not unload directly off of RBCs into the cell. It unloads off of RBCs into the plasma, and the into the cells. This is how diffusion occurs, and why PaO2, although it represents a tiny fraction of total oxygen carriage, is such an important number.


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## phillybadboy (Dec 8, 2011)

thank you, oxygen. diffuses .transported in plasma


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## usafmedic45 (Dec 8, 2011)

phillybadboy said:


> thank you, oxygen. diffuses .transported in plasma



Yes, but remember that the epidermis itself is dead.  No need for oxygen if they're dead. Do you have a problem with comprehending what you are reading?


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## usafmedic45 (Dec 8, 2011)

usalsfyre said:


> Something not well covered in Basic class (or for that matter, some medic classes) is that O2 does not unload directly off of RBCs into the cell. It unloads off of RBCs into the plasma, and the into the cells. This is how diffusion occurs, and



Actually, it doesn't "off-load into the plasma" of the blood.  It offloads either into cells (JP or Veneficus can correct me if I am wrong but I believe it involves the cytochrome P450 enzyme or something like that....I _*hate*_ cell biology).  Now there is oxygen normally carried diffused in the plasma but it is a minority by a vast, vast percentage (see the bolded portion of the equation below for arterial oxygen concentration). 

(Hgb x 1.36 x SaO2) + (*0.0031 x PaO2*)


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## phillybadboy (Dec 8, 2011)

thanks fellas


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## JPINFV (Dec 8, 2011)

usafmedic45 said:


> Actually, it doesn't "off-load into the plasma" of the blood.



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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## usafmedic45 (Dec 8, 2011)

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.


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


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## JPINFV (Dec 8, 2011)

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?


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## usalsfyre (Dec 8, 2011)

Enzyme wise could you be thinking 2,3DPG possibly?


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## JPINFV (Dec 8, 2011)

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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## phillybadboy (Dec 8, 2011)

thanks, fellas


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## phillybadboy (Dec 8, 2011)

usalsfyre said:


> Enzyme wise could you be thinking 2,3DPG possibly?


thanks for this too


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## usafmedic45 (Dec 8, 2011)

usalsfyre said:


> Enzyme wise could you be thinking 2,3DPG possibly?



Nope.  That's intra-erythrocyte enzyme.  



> thanks for this too



Can you explain how it works?


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## phillybadboy (Dec 9, 2011)

i'm gona look into it


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