Tuesday, December 16, 2008

the megakaryocyte story (a gift of self)

I got this picture from: http://path.upmc.edu/cases/case37/images/micro8.jpg Thank you. Sorry, no time to ask permission.

What else can cells tell me about Christmas?

Yah, what else? Hmm...this is getting harder everyday. In trying to think of which cell story reminds me about Christmas, I form a mental picture of cells and their parts. There is a kind of slide show in my mind and I let it ran, then pause for a while, turn around the cell and proceed once more. Now my slide show stopped on... the megakaryocyte.

The megakaryocyte, what kind of cell is it? Well, if you examine the name, “mega” means big and “karyocyte” means a mature cell. So it’s a big, mature cell. Just how big? – about 10 – 15 times bigger than our red blood cells. That’s big! It’s only found in the bone marrow. So if you examine a bone marrow smear under the microscope, it’s the biggest cell around and you can’t miss it, as shown in the picture.

So, what is so special about megakaryocytes and what is Christmassy about it?
Well, megakaryocytes give rise to our platelets by fragmentation of its cytoplasm. Yes, you read that right... its cytoplasm fragments to give rise to platelets, around 2000 – 5000 of them. Imagine that, being fragmented to give rise to little buggers! That is true giving of self, isn’t it?

What remains of the megakaryocyte after this is simply the nucleus with a teeny weeny bit of cell membrane. This then leaves the bone marrow and migrates to the lungs where it is “eaten up” by lung macrophages. I don’t know why it goes to the lungs to die (macrophages are everywhere anyway), but that is how the megakaryocyte story ends.

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