Page 286 - Atlas of Histology with Functional Correlations

RANKL molecule binds to RANK receptors on osteoclasts and stimulates

osteoclast activity

BONE MATRIX

Highly vascularized with blood vessels from periosteum to aid diffusion
through calcified matrix
Organic components of bone resist tension, whereas mineral components
resist compression

Major organic component is coarse type I collagen fibers
Glycoprotein components bind to calcium crystals during mineralization
Inorganic components are calcium and phosphate in the form of
hydroxyapatite crystals

Hormones from the parathyroid gland (parathyroid hormone) and the thyroid
gland (calcitonin) are responsible for maintaining the proper mineral content
of blood

PROCESS OF BONE FORMATION

(OSSIFICATION)

Endochondral Ossification

Most bones develop by this process, with a hyaline cartilage model preceding
bone
Hyaline cartilage model grows in length and width, then calcifies, and
chondrocytes die
Mesenchymal cells in the periosteum differentiate into osteoprogenitor cells

and form osteoblasts
Osteoblasts synthesize the osteoid matrix, which calcifies and traps
osteoblasts in lacunae as osteocytes

Osteocytes establish cell-to-cell communication via canaliculi that open into
blood channels
Primary ossification center forms in the diaphysis and secondary center of
ossification in the epiphysis
Epiphyseal plate between the diaphysis and epiphysis allows for growth in

285