BONE CELLS
&
BONE DEVELOPMENT
In Notebooks! 
Osteogenic cells  osteoblast  osteocyte
Cells of Bone Tissue
Osteoprogenitor
(Osteogenic) Cells
• Embryonic cells that divide to produce
osteoblasts
 Are located in inner endosteum
 Assist in fracture repair
Osteoblasts
 Immature bone producing
cells that secrete matrix
compounds
 not yet calcified to form
bone
 Osteoblasts surrounded by
osseous tissue become
osteocytes
BONE CELLS
Osteocytes
 Mature bone cells that
maintain the bone matrix
 Do not divide
 OSTEON = one unit of
bone tissue
SUMMARY
 Osteogenic cells  osteoblast  osteocyte
Cells of Bone Tissue
Osteoclasts
= “break bone”
 Breaks down bone
 Dissolve bone matrix and release stored
minerals which is taken up by the blood
 Causes osteoporosis
(loss of bone tissue) if
bone is unable to repair
Osteogenesis:
 bone formation
Ossification:
the process of replacing other
tissues with bone
The 2 main forms of ossification:
1) Intramembranous ossification
( dermal ossification)
 occurs in the dermis
 Produces bones such as mandible and
clavicle
2) *Endochondral ossification
 Bone replaces cartilage
 Most bones formed this way
 Observed easily in long bones
STEP 1)
 Chondrocytes in the center of
hyaline cartilage enlarge,
calcify, and die, leaving cavities
in cartilage
STEP 2)
Blood vessels grow around the
edges of the cartilage and cells
begin to change to osteoblasts
Produces layer of superficial
bone around shaft which
becomes compact bone
STEP 3)
Blood vessels enter the cartilage
spongy bone develops at the
primary ossification center in the
shaft where bone tissue replaces
cartilage
 creates a marrow cavity
STEP 4)
 Capillaries and osteoblasts
enter the epiphyses creating
secondary ossification centers
STEP 5)
Epiphyses fill with spongy bone
and there is no cavity in this
region of the bone
On the ends; hyaline cartilage
that remains is
ARTICULAR
CARTILAGE
 At the Epiphyseal plate
(between the diaphysis and epiphysis)
the bone grows lengthwise as bone
tissue replaces cartilage
Epiphyseal Plates become
Epiphyseal Lines
 When long bone stops growing,
after puberty, epiphyseal cartilage
disappears at the growing epiphyseal
plate and an epiphyseal line is visible
on X-rays.