Why don't human red blood cells have nuclei?

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Offline Shadec

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Why don't human red blood cells have nuclei?
« on: 01/11/2010 01:30:05 »
Joel Hillman  asked the Naked Scientists:
Hello brilliant scientists!

I know human blood cells don't have nuclei, but from memory, reptiles do - I haven't looked into it, but I figure its so more haemoglobin can be jammed in. So why do other animals have nuclei, but not people?



What do you think?
« Last Edit: 01/11/2010 01:30:05 by _system »



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Why don't human red blood cells have nuclei?
« Reply #1 on: 01/11/2010 02:11:33 »

Because mammals have a much higher metabolism than fish, amphibians, and reptiles, they need many more red cells and also the size has to be small to squeeze through the small capillaries. Once made the nucleus is pretty much not needed in mammal red cells in order to perform their gas exchange function. Blood cells are made in the bone marrow and the last stage of their development involves excluding their nucleus. Macrophages recycle the components of the ejected nuclei by internalizing them by phagocytosis and breaking them down into basic components inside lysosomes and then returned to the marrow for reuse.