1. BONE CELLS & BONE DEVELOPMENT In Notebooks! 

2. Osteogenic cells  osteoblast  osteocyte

3. Osteoprogenitor (Osteogenic) Cells
Embryonic cells that divide to produce osteoblasts
Are located in inner endosteum
Assist in fracture repair

4. Osteoblasts
Immature bone producing cells that secrete matrix compounds
not yet calcified to form bone
Osteoblasts surrounded by osseous tissue become osteocytes

5. Osteocytes BONE CELLS Mature bone cells that maintain the bone matrix
Do not divide
OSTEON = one unit of bone tissue

6. SUMMARY
Osteogenic cells  osteoblast  osteocyte

7. 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

8. Osteogenesis:
bone formation
Ossification:
the process of replacing other tissues with bone

9. 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

10. STEP 1)
 Chondrocytes in the center of hyaline cartilage enlarge, calcify, and die, leaving cavities in cartilage

11. 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

12. Blood vessels enter the cartilage
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

13. STEP 4)
 Capillaries and osteoblasts enter the epiphyses creating secondary ossification centers

14. On the ends; hyaline cartilage that remains is ARTICULAR CARTILAGE
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

15. * At the Epiphyseal plate
(between the diaphysis and epiphysis) the bone grows lengthwise as bone tissue replaces cartilage

16. 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.