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How do blood cells pass through a capillary?


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#1 scilearner

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Posted 20 April 2010 - 03:10 PM

Hello guys,

A capillary is made up of a single layer of endothelial cells right. So when blood cells pass through it, do the endothelial cells take blood cells up by endocytosis and then release it to other side. Thanks :-)
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#2 Greippi

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Posted 20 April 2010 - 03:49 PM

Normally, blood cells do NOT pass through capillary walls. Capillaries are 'leaky' meaning that plasma and anything dissolved in the plasma will leak through between endothelial cells. Blood cells are just too big to fit. Oxygen, water, and other chemicals pass through the capillary wall.

However, some capillaries called sinusoidal capillaries (found in the liver, bone marrow and other places) have larger openings between endothelial cells and can allow white and red blood cells to pass through.

So the key is: BETWEEN the endothelial cells, not through the cells.

Edited by Greippi, 20 April 2010 - 03:58 PM.

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#3 scilearner

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Posted 20 April 2010 - 04:01 PM

Woops got something wrong there - gimme time to rewrite.


Thanks for the response :-) Are red blood cells smaller than capillaries, or do they squish?

Merged post follows:

Consecutive posts merged

Normally, blood cells do NOT pass through capillary walls. Capillaries are 'leaky' meaning that plasma and anything dissolved in the plasma will leak through between endothelial cells. Blood cells are just too big to fit. Oxygen, water, and other chemicals pass through the capillary wall.

However, some capillaries called sinusoidal capillaries (found in the liver, bone marrow and other places) have larger openings between endothelial cells and can allow white and red blood cells to pass through.

So the key is: BETWEEN the endothelial cells, not through the cells.


This has been another question. How do capillaries take up nutrients, do the endothelial cells take it up intracellularly and then pass it or do they fit into the gap of endothelial cells?

Also if some capillaries can't allow blood cells to pass through, that mean the veins connecting to those capillaries won't have red blood cells right?
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#4 Greippi

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Posted 20 April 2010 - 04:07 PM

A capillary is like a vein - basically a tube. The blood cells pass down the tube. The walls of the capillary are only one cell thick (endothelial cells) - which have spaces between them so stuff from the blood diffuses through the holes in the capillary to the cells beyond the capillary (e.g. liver cells).
So yes, veins connecting capillaries contain blood cells, they just narrow down in size to become capillaries.

A capillary is just big enough for a red blood cell to fit through - but they have to go in single file.

Nutrients just diffuse through the spaces between the capillary cells. The spaces are big enough to allow small molecules (and some are large enough for larger proteins to fit through).
Nutrients that are specifically for the endothelial cells to function are taken up by the cells of course via various active and passive processes.

Hope that makes things a bit clearer.


another thing I thought of: during the immune response, certain types of white blood cells pass through the spaces between the endothelial cells of postcapillary venules via a special process.
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#5 scilearner

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Posted 20 April 2010 - 04:12 PM

A capillary is like a vein - basically a tube. The blood cells pass down the tube. The walls of the capillary are only one cell thick (endothelial cells) - which have spaces between them so stuff from the blood diffuses through the holes in the capillary to the cells beyond the capillary (e.g. liver cells).
So yes, veins connecting capillaries contain blood cells, they just narrow down in size to become capillaries.

A capillary is just big enough for a red blood cell to fit through - but they have to go in single file.

Nutrients just diffuse through the spaces between the capillary cells. The spaces are big enough to allow small molecules (and some are large enough for larger proteins to fit through).
Nutrients that are specifically for the endothelial cells to function are taken up by the cells of course via various active and passive processes.

Hope that makes things a bit clearer.


Hey thanks for help :-) It did make it a lot clear but I still have just one question. Let's say this was a capillary tube

0 0 0 0 0 0 0 0 <----

Then a redblood cell coming in from that direction, how does it pass without getting blocked by an endothelial cell?
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#6 Greippi

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Posted 20 April 2010 - 04:14 PM

Glad to help :)

A capillary is a tube made up of endothelial cells. The cells make a circle, so the cell goes through the hole, there is no block.

Kinda like this cross section:

Posted Image
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#7 scilearner

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Posted 20 April 2010 - 04:22 PM

Glad to help :)

A capillary is a tube made up of endothelial cells. The cells make a circle, so the cell goes through the hole, there is no block.

Kinda like this cross section:

Posted Image


Oh yes lol, thanks again :-) I have just one last question with regard to nutrient uptake by capillary cells. So according to your picture are there minute gaps in the purple region that are not visible. Is it through these gaps that nutrients enter the capillary tube?
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#8 Greippi

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Posted 20 April 2010 - 04:26 PM

The gaps are REALLY TINY compared to the cells - because a single molecule compared to a cell is really tiny. So they wouldn't appear as obvious gaps in the diagram.

In the case of white blood cells passing through these gaps - obviously the gaps are bigger in this type of vessel, but it is still necessary that the shape of the white blood cell distorts and stretches to squeeze through the gap.
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#9 scilearner

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Posted 20 April 2010 - 04:31 PM

The gaps are REALLY TINY compared to the cells - because a single molecule compared to a cell is really tiny. So they wouldn't appear as obvious gaps in the diagram.

In the case of white blood cells passing through these gaps - obviously the gaps are bigger in this type of vessel, but it is still necessary that the shape of the white blood cell distorts and stretches to squeeze through the gap.


Oh I see. Thanks a lot for your help :-) . Upto this time I was thinking about intracellular things. Glad to get back on track :-)
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#10 Greippi

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Posted 20 April 2010 - 04:34 PM

:)
I suppose things COULD pass through the cells. For example water could just diffuse over a concentration gradient through the cell via osmosis. but the easier route would still be between the cells.
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#11 CharonY

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Posted 20 April 2010 - 05:35 PM

Basically small stuff like CO2, O2 and NO can diffuse through the membrane as well as small non-polar molecules. Water does, too however the rate is higher than normal diffusion would allow. The reason is the presence of porins that are permissible to water.
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#12 kellbrook

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Posted 28 March 2012 - 09:06 PM

Basically small stuff like CO2, O2 and NO can diffuse through the membrane as well as small non-polar molecules. Water does, too however the rate is higher than normal diffusion would allow. The reason is the presence of porins that are permissible to water.



okay so tissue like skeletal muscle get nutrients which go through capillaries(paracellularly), and these capillaries are sigle layered. i know some veins or maybe arteries have cappilaries running through them. but some of them don't right? th veins and arteries are multilayered composed of smooth muscle cells and others. for the veins and arteries that don't have cappillaries running through them, i think i know how the cells in the innermost layer get nutrients, but how does nutrient get to cell layers that are not in direct contact with blood, does nutrient go between(paracellular) or through(transcellular) the cells of the inner layers? also the outermost layer does not allow nutrient flow from the intravascular to the extravascular or from the extravascular to the intravascular right?

Edited by kellbrook, 28 March 2012 - 09:36 PM.

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