Review of the Structure and Function of Bone

Question 1

What are the basic components of bone matrix and their principle function?

Answer 1

inorganic matrix (hydroxy appatite) (60-70%)– resists compression
collagen (20-30%)— tensile stregth
water (5-8%)
non-collagenous proteins (5-8%)

Question 2

What are the 3 major blood supplies to a long bone?

Answer 2

periosteal vessels (cortical bone)
nutrient vessels (to medullary bone)
metaphase vessels (metaphaseal plate)

notice bones surrounded by more connective tissue tend to heal better (i.e. surrounded by muscle)

Question 3

Contrast the two types of bone by discussing the type of strain they accommodate best.

Answer 3

trabecular/cancellous bone absorbs force, able to deform before failing

cortical/ compact bone transfers force and resists compression

Question 4

What is the role of osteoblasts? What lineage do they come from?

Answer 4

regulates formation and deformation

produces collagen, acts as regulatory cell and comes from a mesenchymal lineage

Question 5

What is the role of osteoclasts? What lineage do they come from?

Answer 5

osteocyte is a matured osteoblast that is surrounded by a haversian system also comes from the mesenchymal lineage

Question 6

What is the role of osteoclasts and what lineage are they produced from?

Answer 6

from the hematopoetic lineage, with many nuclei and ruffled border they act to break down one

Question 7

What are two opposing bone signaling molecules that control formation and degradation of bone?

Answer 7

RANKL causes osteoclast progenitors to become active and OPG causes them to be inactive

Question 8

How are RANKL and OPG regulated?

Answer 8

effects of Vit. D, PTH, PGE2, IL-1 are interpreted by osteoblasts that control RANKL, OPG levels

this becomes important in situations of cancer, osteoporosis and fracture healing
the balance of RANKL and OPG regulates cell size and growth (varies with different tumors)

Question 9

What molecule acts directly on osteoclasts?

Answer 9

biscphophonates disrupt the osteoclast ruffled border/cause apoptosis

Question 10

Order these forces on how well bone withstands them: tension, shear, compression.

Answer 10

bone withstands compression best, it is weaker in withstanding tension and weaker yet with shear force

Question 11

Steeped transverse fracture surface results due to ____ failure while oblique fracture is due to ___ failure.

Bending with axial load results in a ___ fracture, torsion results in ____ fracture.

Answer 11

stepped transverse- tensile failure
oblique- shear failure

butterfly- bending with axial load (tension on one side, compression on the other)
spiral - torsion load