MadSci Network: Cell Biology

Re: What are the specialized parts of an osteocyte?

Date: Thu Dec 7 11:27:11 2006
Posted By: William Gunn, Grad student, The Center for Gene Therapy, Tulane University
Area of science: Cell Biology
ID: 1165284560.Cb

Hi Suzy. If I understand your question, you're asking what makes osteocytes different from other cells. You are correct that an osteocyte does have the same organelles as other cells, such as a golgi apparatus and ribosomes. However, since an osteocyte is relatively dormant and encased in a matrix of calcium and hydroxyapatite(the stuff that makes up bone), it does not grow and divide like other cells and therefore the ER and Golgi are less active than in other cells. The University of Auckland in New Zealand has a good basic description of the parts of an osteocyte.

Though the cells are encased in lacunae, or pockets within the compact bone, they remain connected to one another by tiny canals called canaliculi, through which a portion of the cell membrane extends, allowing the cells to touch and communicate and also to have access to the blood stream. You can see some pictures and schematic drawings of these structures if you do a google image search for osteocyte. It is thought that these canaliculi allow osteocytes to modify bone density in response to mechanical stress. The volume of the canaliculi in areas of increased stress is reduced, resulting in a flow of fluid from the compressed canaliculi to less compressed canaliculi, and this flow is has a stimulatory effect on the osteocytes, possibly allowing them to increase the density of the bone in their local area. There's more about this process here.

As far as the nucleus goes, it's mostly heterochromatic, as you would expect in a mostly dormant cell.

I hope this answers your current question and brings up some new ones. If it does, and you can't satisfy your curiosity by searching the web, you know where to ask!

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