Bone Structure / Function

Question 1

How do long / short bones form?

What protein suppresses long bone growth?

Answer 1

Endochondral ossificiation

FGFR3

Question 2

How do flat bones form?

Answer 2

Intramembranous ossification, which involves loose condensations of mesenchymal tissue.

Question 3

Which genes stimulate osteoblast growth?

What happens if gene is mutated?

Answer 3

Cbfa1 and RUNX2. If lose 1 copy, flat bones are damaged.

Question 4

3 sources of blood supply for bones

Answer 4

Nutrient arteries (supply inner 2/3), periosteal membrane arteries (supply outer 1/3) and metaphyseal complex

Question 5

Cells of origin for osteoblasts, osteoclasts, and osteocytes

Answer 5

Blasts / cytes come from mesenchymal cells.

Clasts come from hematopoietic lineage (similar to macrophages)

Question 6

What is osteocalcin?

Answer 6

Marker for osteoblastic activity

Question 7

Where do osteoclasts live?

Answer 7

Howship’s lacunae

Question 8

What does osteoprotegerin do?

Answer 8

Stops bone breakdown by binding to RANK ligand on osteoblasts, preventing binding of RANK on osteoclasts.

Question 9

Which cancers favor RANKL vs OPG?

Answer 9

RANKL: giant cell tumor, MM, breast cancer
OPG: prostate cancer

Question 10

Teriparatide

Answer 10

Recombinant PTH. Only anabolic treatment

Question 11

Denosumab

Answer 11

RANKL Ab. Acts similar to OPG by preventing osteoclast activation.