BONE CELLS
&
BONE DEVELOPMENT
In Notebooks!
Osteogenic cells osteoblast osteocyte
Cells of Bone Tissue
Osteoprogenitor
(Osteogenic) Cells
Are located in inner endosteum
Assist in fracture repair
• Embryonic cells that divide to produce osteoblasts
Osteoblasts
Immature bone producing
cells that secrete matrix
compounds
not yet calcified to form
bone
Osteoblasts surrounded by
osseous tissue become
osteocytes
Osteocytes
Mature bone cells that
maintain the bone matrix
Do not divide
OSTEON = one unit of
bone tissue
BONE CELLS
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.