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.