I have just found out that white blood cells are larger than red blood cells and now I'm confused due to something I learnt in class. Basically, I was taught that there were spaces between the endothelial cells lining the capillary and these spaces allow white blood cells to escape and enter infected tissues to help clear out the infection. Why don't the red blood cells escape then if they are smaller than white blood cells they should fit through the spaces as well right?

  1. there are several types of white blood cells (at least 4) and they vary greatly in size from type to type.

  2. white blood cells are not rigid, they can squeeze through very small openings. it always buts me in mind of watching a octopus squeeze into a bottle.

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  • $\begingroup$ So are red blood cells rigid and thats why they can't go through the small spaces between the cells? Also what happens to the white blood cells once they get to the infection? Are they broken down or do they manage to enter the capillary again? $\endgroup$ – James Oct 19 '18 at 17:33
  • $\begingroup$ they are more rigid, but more specifically lack the mechanism that actually squeezes the cell through, it is not a passive process, the white blood cells is physically pushing itself through the gap similar to how an amoeba moves. The last question would be a great seperate question. $\endgroup$ – John Oct 19 '18 at 17:35
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    $\begingroup$ I should point out that RBC precursors do need to extravasate through bone marrow endothelium to end up in the blood to begin with, but if you look at reticulocyte morphology, for example, there's a big difference compared to a terminally differentiated RBC. $\endgroup$ – CKM Oct 19 '18 at 17:49
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    $\begingroup$ Thank you for your comment CKM but I have no clue what your talking about lol. Your too clever for me :) Can you explain what you said in an easier way please? If not it is okay but I'm only in my first year of biology yet and so I don't know much other than the basics. $\endgroup$ – James Oct 19 '18 at 17:51

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