Bone formation

Question 1

Endochondral ossification

Answer 1

Bones of axial and appendicular skeleton,
Base of the skull

Cartilage by chondrocyte, later replaced with woven bone, and remodel to lamellar bone.

Question 2

Woven bone occurs when

Answer 2

In adults,

after fracture and Paget’s disease

Question 3

Membraneous ossification

Answer 3

Bones of calvarium (skull) and facial bone

Woven bone formed without cartilage
Later remodeled to lamellar bone

Question 4

PTH

Answer 4

At low, intermittent level,
anabolic (building bone) on osteoblast, osteoclast

At chronic, high level,
catabolic (osteitis fibrosa cystica)

Question 5

Estrogen

Answer 5

Inhibits apoptosis of osteoblasts

Induces apoptosis of osteoclasts

Question 6

Achondroplasia

Answer 6

Failure of longitudinal bone growth
(endochondral ossification)

Constitutive FGFR3 actually inhibits chondrocyte proliferation.

> 85% sporadic mutation, associated with adv paternal age
Also autosomal dominant pattern.