Metabolic bone disorders Flashcards
What are the two components of bone?
- Osteoid: unmineralised bone (organic component)
- 35%
- Mainly Type I collagen fibres
- Inorganic minergal component
- 65%
- Calcium hydroxyapatite crystals (that fill the space between the collagen fibres)
What is the function of the osteoblasts?
They built boneby synthesising collagen fibres and help in osteoid mineralisation
What is the function of osteoclasts?
They resorb bone and thereby free calcium and phosphate via the release of lysomal enzymes
How do osteoclasts get activated?
They differentiatiate in response to RANKL-Receptor stimmulation of surface
The RANKL is expressed on osteoblasts surfaces–> osteoclasts get activated by osteoblasts!
How to osteoblasts get activated?
Resond to PTH & calcitriol (1,25 (OH)2 vit D)
–> regulate bone formation and absorbtion
What is the cortical part of the bone?
The hard shell of the bone
What is the Trabecular part of bone?
spongy, inner part of bone
What is meant by the term “woven” bone
disorganised collagen fibrils, weaker
–> loss of lamellar sturcture
How do you call a bone that is weaker due to unoranised collagen fibres?
Woven bone
What is the normal structure of a bone called?
Lamellar pattern of bone :
collagen fibrils laid down in alternating orientations that makes it mechanically strong
What are the direct effects of Vitamine D deficiency on bone?
Inadequate mineralisation of newly formed bone matrix (osteoid)
How does Vitamin D deficiency present in children?
Rickets
- skeletal abnormalities and pain, growth retardation, increased fracture risk
- also affects cartilage and epiphysal growth
What does Vit D deficiency cause in adults?
OSTEOMALACIA
- affects the bone (not the epiphysal)
- skeletal pain, increased fracture risk, proxmyopathy
–> might lead to wabbeling gait and looser zones (in severe deficiency)
What is a looser zone in bone?
Fractures from inadequadly mineralised bone due to normal weight
Explain primary, secondary and tertiary Hyperparathyroidism