1. Osteogenesis or Ossification
Bone Development
Osteogenesis or Ossification

2. Bone Development
Osteogenesis = ossification is the process of bone tissue formation.
In embryos, this leads to the formation of the bony skeleton.
In children and young adults, ossification occurs as part of bone growth.

4. Bone Development In adults, it occurs as part of bone
remodeling and bone repair.

5. Formation of the Bony Skeleton
Before week 8, the human embryonic skeleton is made of fibrous membranes and hyaline cartilage.
After week 8, bone tissue begins to replace the fibrous membranes and hyaline cartilage.

6. Types of Ossificaiton cranial bones and clavicles rest of skeleton
1. Intramembraneous Ossification
development of bone from a fibrous membrane
cranial bones and clavicles
2. Endochondral Ossification
replacement of hyaline cartilage with bone
rest of skeleton

7. Intramembraneous Ossification

8. osteoblasts within connective tissue membranes begin to produce a matrix of bone

9. results in enlarging trabeculae that surround blood vessels

10. matrix continues to enlarge and thicken, trapping the osteoblasts which will mature into osteocytes

11. Intramembraneous Ossification
osteoblasts within connective tissue membranes begin to produce a matrix of bone
results in enlarging trabeculae that surround blood vessels
matrix continues to enlarge and thicken, trapping the osteoblasts which will mature into osteocytes

12. Endochondral Ossification

14. starts with bone collar on the outside and a central ossification center in diaphysis
after birth, growth occurs when epiphyseal plate enlarges (mitosis) on distal face
hyaline cartilage broken down and replaced by bone except at epiphyseal cartilage areas
chondrocytes on proximal face atrophy and osteoblasts form medullary cavity
cartilage “bones” serve as a pattern for osseous bone construction

15. Endochondral Ossification
cartilage “bones” serve as a pattern for osseous bone construction
hyaline cartilage broken down and replaced by bone except at epiphyseal cartilage areas
starts with bone collar on the outside and a central ossification center in diaphysis
after birth, growth occurs when epiphyseal plate enlarges (mitosis) on distal face
chondrocytes on proximal face atrophy and osteoblasts form medullary cavity

16. Increasing the Diameter of Bone
Ossification complete by age 25.

17. Bone Remodeling

18. Bone Remodeling Caused by:
hormones, gravity, and physical stress (exercise)
large volumes of bone are removed and replaced on a continual basis
Bone remodeling in young adults keeps mass the same.
In old age, reabsorption gets ahead.

19. Osteoporosis

20. Osteoporosis bone reabsorption outpaces bone deposit
bone composition the same but bone mass reduced
bones become porous

21. Osteoporosis
compression fractures of vertebrae and easily broken bones results (especially femur neck)
problem in older
women because
least dense bones
and smallest bones
to begin with

22. Osteoporosis treated by reversing the above Causes:
estrogen deficiency
lack of exercise
low intake of calcium, protein, and vitamin D
treated by reversing the above
Osteoporosis

23. Fractures

24. Types of Fractures Simple (closed) Compound (open) Comminuted
clean break
Compound (open)
ends penetrate skin or other soft tissue
Comminuted
fragmented
Greenstick
break incomplete like a green twig, common in children

25. Steps of Fracture Repair
treated by reduction (bone ends returned to normal position, realignment) and immobilization by cast or traction
6 to 8 weeks of healing begins (longer in elderly)

27. Steps of Fracture Repair
hemotoma (clot) surrounds broken bone ends
collagen fibers span the break while osteoclasts dissolve edges
debris cleaned up by phagocytes
cartilage cells secret cartilage matrix

28. Steps of Fracture Repair
3. within cartilage, osteoblasts form soft calcium rich new bone - callus
4. callus remodeled and hardened - bone healed

29. Changes in Bone Through Life
long bone ossification begins at 8 wks
hyaline cartilage “long bones” primary ossification centers - 12 wks
birth mostly epiphysis left
hormones cause growth during childhood and adolescence spurt
bone markings develop with muscles
black males - bones more dense