Osteoperosis Flashcards
What’s the purpose of bone?
Protects vital organs
Stores minerals (99% of calcium is in bone- 179 uses in the body)
Primary site for production of RBC & WBC
Support & Movement
What’s the trabecular bone & it’s density?
Mainly found at joints (epiphysis)
5-50% density
What’s the cortical bone and it’s density?
Mainly in diaphysis (shaft) but also cortical shell at epiphyses.
50-90% density
What is collagen?
Protein found in bone.
2/3 bone volume & 1/3 bone mass
Strong in tension
What’s the mineral uses in bone?
Attenuates X-rays
Strong in compression
How can bone strength be measured?
DXA = duel-energy X-ray absorptiometry pQCT = peripheral quantitative computed tomography
What’s the advantage of DXA?
Cheap
Quick (5-10 minutes)
Applicable at fracture prone sites
Large reference databases
What are the disadvantages of DXA?
Can’t assess bone geometry
Influenced by body size
What are the advantages of using pQCT?
Can assess bone geometry
What’s the disadvantage of pQCT?
Can’t be applied at central sites
What’s osteopenia?
Where protein and mineral content of bone tissue is reduced but less severely than osteoporosis.
What’s osteoporosis?
Bones become brittle and fragile from loss of tissue, typically as a result of hormonal changes or deficiency of minerals.
How many osteoporotic fractures occur in US each year?
> 2 million which costs $17 billion
What contributes to bone strength?
Mineralisation
Porosity
Collagen structure
Trabeculae- number/spacing/orientation
What’s the bone maximal strength at one time?
180MPa
What’s the maximal compressive stress on bone?
180MPa
130MPa when tensed
What’s the function of osteoclasts?
Break down bone
What’s the function of osteoblasts?
Generate collagen & mineralise osteoid (the unmineralised organic component of bone)
What’s the function of osteocytes?
Control activity of osteoclasts and osteoblasts
How does oestrogen have an effect on bone?
It reduces osteoblasts death but inhibits osteoblasts activity & proliferation.
What happens when there’s low blood Ca2+ levels?
Parathyroid gland senses
Secretes parathyroid hormone (PTH)
Stimulates osteoclasts activity
Reabsorption of bone releases Ca into blood
What’s happens when there is high blood Ca2+ levels?
Thyroid gland senses this
Secretes calcitonin
Hormone stimulates osteoblast activity
Formation of bone removes Ca from blood
What’s the most common place for fractures?
Radial bone at the wrist
Femoral neck (hip bone)
Lumbar vertebrate
What’s the process of bone making from connective tissues at 8 weeks called?
Ossification
What’s the two different methods of ossification?
Intramembranous- forms bones of skull from fibrous membranes
Endochondral- replaces hyaline cartilage to form majority of bones other than skull.
Where is hyaline cartilage found?
Covers epiphysis & diaphysis
How does bone grow?
Cartilage Cells in growth plate divide pushing epiphysis away. Cartilage in epiphyseal plate adjacent to diaphysis is replaced by bone. Eventually plate disappears and E & D fuse.
How much of adults Skelton can be replaced annually?
10%
What are the two distinct stages of bone remodelling?
Bone reabsorption
Bone deposition
List the factors influencing osteoporosis
Age Sex Ethnicity Genetics Nutrition Pregnancy/ lactation Menopause Body size Disease
What’s the diagnosis criteri for osteopetosis?
Bone mineral density 2.5 SD below average young
