Biology Reference
In-Depth Information
Calvaria
Long bone
Collagen
8.8
Osteoglycin
4.0
PEDF
2.6
2.2
Osteopontin
6.8
Thrombin
3.2
Spp24
2.6
Osteonectin
3.7
Fetuin
3.8
Thrombospondin-1
2.6
Chondrocalcin
10
8
6
4
2
0
2
4
6
8
Fig. 8.11 The composition of calvaria bone differs considerably from that of long bone as
depicted in this figure. The fold difference is shown for a number of bone-associated proteins.
PEDF
pigment epithelium derived factor,
Spp24
secreted phosphoprotein 24 [Data derived from
Van den Bos et al. (
2008
).]
8.2.8 The Osteoclast Retracts and Moves Away to Another Site
The osteoclast resorbs the bone up to a certain depth and then moves away from that
site. Under normal conditions the cell does not continue resorbing the bone at one
site, for yet unknown reasons it stops eating at a certain time point. One possible
explanation has been recently suggested by Wilson et al. (
2009
). These authors
noted that collagen fragments generated by cathepsin K were able to inhibit the
resorption of the osteoclast. It could thus be that compounds released by the
osteoclast during the resorption process modulate its activity.
8.2.9 Cleaning of the Resorption Pit by Bone Lining Cells
Following resorption the osteoclast leaves the resorption pit, the Howship's lacuna.
During normal bone remodelling the lacuna is subsequently occupied by bone
forming osteoblasts and new bone is deposited at that site (Parfitt
2000
). Prior to
the bone-forming activity, however, bone lining cells enter the lacuna and clean the
