Physiology of bone repair

Question 1

Osteoclasts

Answer 1

function: resorption
multinucleate

bone degradation and formation

resorption occurs at the ruffled border

Question 2

Bisphosphonates

• indication
• example
• mechanism of action

Answer 2

for osteoporosis

e.g. alendronate

inhibit osteoclast-mediated bone-resorption

Question 3

Teriparatide

Answer 3

for osteoporosis

-portion of human PTH

encourages osteoblast formation of bone

Question 4

Denosumab

Answer 4

monoclonal antibody

targets RANKL inhibiting it

osteoporosis

Question 5

Osteopetrosis

Answer 5

Autosomal recessive genetic disorder

Osteoclasts cannot remodel bone due to defective ion channel

leads to excessive bone growth

symptoms: Blindness
Deafness
Severe anaemia

Question 6

How does PTH stimulate resorption via osteoblasts

Answer 6

On osteoblast- PTH-R (PTH binds) and RANKL (RANK binds)

activates osteoclasts and stimulates them to carry out bone resorption

Question 7

What does vit D do?

Answer 7

Increases intestinal Ca2+ absorption (inreases calbindin)

stimulates kidneys to reabsorb more calcium

stimulates osteoclasts (via osteoblasts)

facilitates bone remodelling and thus increases serum Ca2+

Question 8

Consequences of chronic hypocalcaemia

Answer 8

Skeletal deformities

Rickets

Bone fractures

Impaired growth

Short stature

Dental deformities

Question 9

Consequences of acute hypocalcaemia

Answer 9

Convulsions
Arrhythmia
Tetany (Trousseau’s Sign, Chvostek’s Sign)

Question 10

Effect of hypocalcaemia on the membrane potential of cells

Answer 10

increases excitability
as more sodium can leak through

threshold for AP is lowered

Question 11

Hypercalcaemia

Answer 11

Lowered excitability

Fatigue, depression, constipation

severe (can lead to coma, cardiac arrest)