red blood corpuscles

Nick Theodorakis nicholas_theodorakis at urmc.rochester.edu
Thu Oct 28 09:17:02 EST 1999


In article <7v7q18$ltc$1 at pravda.ucr.edu>, jobin at unser.ucr.edu (Jobin
James) wrote:
> pardon me if this is the
> wrong newsgroup.
> if so, please direct me
> to the correct one.

You might also try one of the sci.med groups (I think there is a
sci.med.blood - or something like that).

> i have 3 questions about
> red blood corpuscles.

These answers are from memory, not from having a textbook in front of
me, so take them for what they are worth:


> - how many RBCs does a human body have?

IIRC, RBCs are a few billion (i.e.,  a few times 10 exp9) per ml of
blood. I think there is about 5 l of blood in an average size person.

> - how long does an RBC live?

about 120 days, again, IIRC

> - what happens to an RBC after it dies?
> 	is it flushed out of the system?

First, note that for a mature RBC, "dying" is somewhat of a fuzzy term,
since it depends on what you meam by "living." They don't have nuclei,
they don't do macromolecular synthesis or oxidative phosphorylation,
and their metabolism is pretty simple.

When they get old, the liver removes them from circulation, and
degrades them. Surface glycoproteins and other polysacharides on RBCs
have sialic acid on the ends of their sugar chains. After time, they
lose their sialic acid. Specialized receptors (called the
asialoglycoprotein receptor) on liver cells recognize the sialic
acid-less glyoproteins, and bind to them, leading to internalization
and degradation.

Heme (from hemoglobin) is degraded into bilirubin, which gets modified
into a water-soluble form, and excreted. (Which is why newborns
sometimes get hyperbilirubinemia, because their liver has a hard time
getting rid of bilirubin at first, until their liver gets a little more
mature).

> this is not a homework problem :)
> i need them for a story i'm writing.
> just wanted to be accurate.

Then a trip to the library would probably be in order.




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