1. Bone Formation, Growth, and Remodeling

2. Ossification Ossification – Process of bone formation
Steps in Ossification
1) Hyaline cartilage is used to form a model
2) Hyaline cartilage model is
covered with bony matrix by
osteoblasts
3) The enclosed hyaline
cartilage is digested away
- This accounts for the
medullary cavity

3. Bone Remodeling Cells
Osteoblasts - Bone forming cells that secrete the matrix
- These are the cells
responsible for
making bone and
storing minerals
B for blast, B for build

4. Bone Remodeling Cells (Cont.)
Osteoclasts – Giant bone destroying cells
- Break down the
matrix to release
calcium

5. Appositional Growth This is how bones widen as they grow longer
Steps in Appositional Growth
1) Osteoblasts in the periosteum add bone
to the external face of the diaphysis
2) Osteoclasts in the endosteum remove
bone from the inner face of the diaphysis

6. What controls the process of long bone growth?
Human Growth Hormone – Secreted by the pituitary gland
Sex Hormones – Testosterone and Estrogen
Bone growth ends during adolescence when the epiphyseal plates are converted to bone

7. Regulating Blood Calcium
When blood calcium drops: Parathyroid releases parathyroid hormone – This stimulates osteoclasts to destroy bone matrix to release calcium into the blood
When blood calcium is too high: It is called hypercalcemia – Calcium is deposited in the matrix as calcium salts

8. What is Ricket’s?
Disease in children in which the bones fail to calcify and harden
Can be recognized by bowed legs
Due to a lack of calcium and/or vitamin D

9. Fractures
Simple Fracture – The bone breaks cleanly but does not penetrate the skin

10. Fractures (Cont.) Compound Fracture – Broken bone end
sticks out of skin
- Can easily become
infected if not
handled properly

11. Bone Fractures The bone breaks into many fragments
Comminuted Fracture
The bone breaks into many fragments
Common in older individuals because their bones are brittle

12. Bone Fractures (Cont.) Compression Fracture – The bone is crushed
Common in porous bones
Example: Vertebrae

13. Bone Fractures (Cont.) Depressed Fracture – Broken bone portion
is pressed inward
- Typical of a skull
fracture

14. Bone Fractures (Cont.)
Impacted Fracture – The bone ends are forced into each other
Common when breaking a fall

15. Bone Fractures (Cont.)
Spiral Fracture – Very ragged fracture that occurs from excessive twisting
Common sports fracture

16. Bone Fractures (Cont.)
Greenstick Fracture – The bone breaks incompletely, like a green twig
Common in children

17. Reduction of Fractures
Open
Reduction
Open Reduction – Surgery is performed and the bones are pinned or screwed into place
Closed Reduction – Doctor sets the bone with his hands
Closed
Reduction

18. Repairing Bone Fractures
1) A hematoma (blood filled swelling)is formed due to blood vessels being damaged during break.
2) The break is splinted by a fibrocartilage (soft)
callus. This callus is composed of various
connective tissue and functions to keep the break
stabilized.
3) The bony callus forms. This callus replaces the
fibrocartilage callus with spongy bone.
4) Bone remodeling occurs. The bony callus is
remodeled to form a strong permanent patch at the
fracture site.