Msk Week 2 Objective 4 (C,d)

Front 1

What is Wolff's law?

Back 1

"Bone will adapt to loads it is placed under"
If increased stress, the bone will become stronger by increasing its diameter.
If decreased stress the bone will adapt and become weaker.

Front 2

Is bone modeling or remodeling occurring in Wolff's law?

Back 2

Remodeling - via osteoblast and osteoclast activity.

Front 3

How is bone remodeling regulated?

Back 3

1) Systematically
- growth hormones, thyroid and parathyroid
- Calcium, calcitonin, cortisone
2) Locally
- mechanical lesions (fractures, defects, implants
- Inflammation (infection, arthritis)
- Blood supply

Front 4

How does the parathyroid affect mineral homeostasis?

Back 4

PTH increases serum Ca+2 levels.
The osteoblasts have receptors for PTH on its surface, which when bound induces the production of osteoclast stimulating hormone (OSH) from the osteoblast.
The OSH activates the osteoclast to increase bone resorption which increases the amount of Ca+2 in the blood.

Front 5

What does anabolic activity mean in relation to bone? Catabolic activity?

Back 5

Anabolic = bone formation via increased or osteoblast activity or decreased osteoclast activity.
Catobolic = bone resorption via increased osteoclast activity or decreased osteoblast activity

Front 6

What role do osteocytes have in regulating bone strength?

Back 6

During stress, the strain is sensed. The osteocytes are effector cells that respond to the strain by signaling altered osteoclast/osteoblast activity.

Front 7

How does bone grow in girth size?

Back 7

Periosteal bone formation
Osteoblasts lay down bone under the periosteum while osteoclasts resorb bone at the endosteum.
This makes the tube of the bone greater in diameter while maintaining the density of bone.
Goal = maintaining strength with the minimal amount of bone.

Front 8

What role do osteocytes have in regulating bone strength?

Back 8

During stress, the strain is sensed. The osteocytes are effector cells that respond to the strain by signaling altered osteoclast/osteoblast activity.

Front 9

How does bone grow in girth size?

Back 9

Periosteal bone formation
Osteoblasts lay down bone under the periosteum while osteoclasts resorb bone at the endosteum.
This makes the tube of the bone greater in diameter while maintaining the density of bone.
Goal = maintaining strength with the minimal amount of bone.

Front 10

What role do osteocytes have in regulating bone strength?

Back 10

During stress, the strain is sensed. The osteocytes are effector cells that respond to the strain by signaling altered osteoclast/osteoblast activity.

Front 11

How does bone grow in girth size?

Back 11

Periosteal bone formation
Osteoblasts lay down bone under the periosteum while osteoclasts resorb bone at the endosteum.
This makes the tube of the bone greater in diameter while maintaining the density of bone.
Goal = maintaining strength with the minimal amount of bone.

Front 12

How does the bone respond to increased load strain?

Back 12

Increases its inertia by increasing the diaphysis cross sectional area while maintaining the same density. This occurs via periosteal girth formation.
Greater diameter = greater inertia = greater bone strength

Front 13

Based on the forces applied to bone in this diagram, what cells will be acting where to adapt the bone to the applied stress?

Back 13

The bone will be thickening on the side with increased compression forces therefore osteoblast activity will be increased here. Comparably, the bone will likely thin on the side with less strain (tensile forces).