1. Bone Remodeling
_______________ units – adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces

2. Bone Deposition
Occurs where bone is ____________ or added strength is needed
Requires a diet rich in ____________, vitamins ___, ___, and ___, calcium, phosphorus, magnesium, and manganese
____________ ____________ is essential for mineralization of bone

3. Sites of new matrix deposition are revealed by the:
Bone Deposition
Sites of new matrix deposition are revealed by the:
___________ ___________ – unmineralized band of bone matrix
____________ __________ – abrupt transition zone between the osteoid seam and the older mineralized bone

4. Accomplished by ______________
Bone Resorption
Accomplished by ______________
Resorption bays – grooves formed by osteoclasts as they break down bone matrix
Resorption involves osteoclast secretion of:
____________enzymes that digest organic matrix
Acids that convert __________ __________ into soluble forms

5. Bone Resorption
Dissolved matrix is transcytosed across the osteoclast’s cell where it is secreted into the interstitial fluid and then into the blood

6. Importance of Ionic Calcium in the Body
Calcium is necessary for:
Transmission of __________ _____________
Muscle _____________
Blood ______________
Secretion by _________ and _________ ________
Cell ___________

7. Two control _______ regulate bone remodeling
Control of Remodeling
Two control _______ regulate bone remodeling
Hormonal mechanism maintains calcium homeostasis in the ___________
Mechanical and _______________ forces acting on the skeleton

8. Hormonal Mechanism
Rising blood Ca2+ levels trigger the thyroid to release _____________
___________ stimulates calcium salt deposit in bone
Falling blood Ca2+ levels signal the ___________ glands to release PTH
PTH signals osteoclasts to degrade bone matrix and release ______ into the _________

9. Hormonal Control of Blood Ca
PTH;
calcitonin
secreted
Calcitonin
stimulates
calcium salt
deposit
in bone
Thyroid
gland
Rising blood
Ca2+ levels
Imbalance
Calcium homeostasis of blood: 9–11 mg/100 ml
Falling blood
Ca2+ levels
Imbalance
Thyroid
gland
Osteoclasts
degrade bone
matrix and release
Ca2+ into blood
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH)
PTH
Figure 6.11

10. Response to Mechanical Stress
_________ law – a bone grows or remodels in response to the forces or demands placed upon it
Observations supporting ________ law include
Long bones are thickest _________________ (where bending stress is greatest)
Curved bones are thickest where they are most likely to ____________

11. Response to Mechanical Stress
Trabeculae form along lines of stress
Large, bony projections occur where heavy, active muscles attach

12. Response to Mechanical Stress
Figure 6.12

13. Bone Fractures (Breaks)
Bone fractures are classified by:
The position of the ________ ________ after fracture
The ______________ of the break
The ______________ of the break to the long axis
Whether or not the bones ends penetrate the _____

14. Types of Bone Fractures
_____________ – bone ends retain their normal position
_____________ – bone ends are out of normal alignment

15. Types of Bone Fractures
___________ – bone is broken all the way through
___________ – bone is not broken all the way through
___________ – the fracture is parallel to the long axis of the bone

16. Types of Bone Fractures
_____________ – the fracture is perpendicular to the long axis of the bone
__________ (open) – bone ends penetrate the skin
__________ (closed) – bone ends do not penetrate the skin

17. Common Types of Fractures
______________ – bone fragments into three or more pieces; common in the elderly
_____________ – ragged break when bone is excessively twisted; common sports injury
_____________ – broken bone portion pressed inward; typical skull fracture

18. Common Types of Fractures
_______________ – bone is crushed; common in porous bones
_______________ – epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying
_______________ – incomplete fracture where one side of the bone breaks and the other side bends; common in children

19. Stages in the Healing of a Bone Fracture
___________ formation
Torn blood vessels hemorrhage
A mass of clotted blood (hematoma) forms at the fracture site
Site becomes swollen, painful, and inflamed
Figure

20. Stages in the Healing of a Bone Fracture
Fibrocartilaginous ________ forms
_____________ tissue (soft callus) forms a few days after the fracture
_____________ grow into the tissue and __________ cells begin cleaning __________
Figure

21. Stages in the Healing of a Bone Fracture
The fibrocartilaginous callus forms when:
Osteoblasts and fibroblasts migrate to the fracture and begin reconstructing the bone
Fibroblasts secrete collagen fibers that connect broken bone ends
Osteoblasts begin forming spongy bone
Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies

22. Stages in the Healing of a Bone Fracture
_________ callus formation
New bone trabeculae appear in the fibrocartilaginous callus
Fibrocartilaginous callus converts into a bony (hard) callus
Bone callus begins 3-4 weeks after injury, and continues until firm union is formed ______ months later
Figure

23. Stages in the Healing of a Bone Fracture
Excess material on the bone shaft exterior and in the medullary canal is removed
Compact bone is laid down to reconstruct shaft walls
Figure