Bones and Joints Flashcards
Normal bone
Constituents and purpose of each
Outer solid cortical bone - mechanical Inner trabecular (spongy) bone - mechanical and hosts bone marrow for metabolic fx Outer surface - periosteum Inner space (medulla) contains fat or haemopoietic marrow
65% inorganic (mineralised) - mainly calcium salts
35% organic
Functions
Mineral homeostasis - bone acts as vessel for calcium
Houses haemopoietic system i.e bone marrow
Mechanical - differentiates us from vertebrates - not a static scaffold - constantly remodelled
Bone diseases - consists of
Infection
Tumours
Trauma/degeneration
Specific derangements of bone’s particular specialised processes and function
Specific bone diseases
Infections
Tumour
Trauma
Disorders of matrix formation
Disorders of mineralisation
Disorders of bone turnover
Bone remodelling cycle
Activation of osteoclasts Resorption of bone Death of osteoclasts Formation of new matrix by osteoblasts Mineralisation of new matrix Quiescence = BASIC MULTICELLULAR UNIT
Two cell types run bone
Key to maintaining bone strength
What can go wrong - what happens in osteoporosis
Osteoblasts and clasts are coupled
Coupling lost in osteoporosis –> loss of bone volume
Calcium physiology
Defective matrix/ matrix formation
Mineralisation problems
Turnover problems
Bone matrix formation diseases - rare
Mutations in collagen - type 1 --> Osteogenesis imperfecta, affects ears, eyes, skin and teeth - greater risk of fractures Other abnormalities - mucopolysaccharidoses --> morquio syndrome --> Hurler syndrome
Cartilage matrix formation disorders - uncommon
Bone usually grows longitudinally at the growth plates
Achondroplasia
- autosomal dominant
- failure of cartilage maturation at the growth plate
- mutation of fibroblast growth receptor 3
- -> continually activated negative regulator of growth
Diseases of mineralisation - uncommon
Vit D is activated in kidney
Osteomalacia/Rickets
- deficiency in Vit D or calcium
- dietary or metabolic
- failure to mineralise to cartilage overgrowth –> failure of longitudinal growth
If deficient, skeleton is not mineralised properly
Bone remodelling problems
- osteoporosis - Increased porosity of bone due to a reduction in bone mass
Osteoporosis
Risk factors
Increased porosity of bone due to a reduction in bone mass
- Age
- Hormonal influences - loss of sex steroids
- Lifestyle
- Activity
- Genetics
- Nutrition
Osteoporosis - mechanism
Which bone is lost first
Uncoupling of bone resorption and formation
- too much resorption
- too little formation
- loss of trabecular bone initially
Osteoporosis - complications and treatment e.g??
- fragility fractures (vertebrae, femoral neck, distal radius)
- kyphosis (Dowager’s hump)
- Loss of height
- Inhibit bone resorption with BISPHOSPHONATES
- increase bone formation with experimental treatment e.g parathyroid hormone
Disorders of abnormal turnover
Which disease?
Common in
PAGET’S disease aka OSTEITIS DEFORMANS
Excess turnover
Progressive deformity of individual bones
3 phases :
Osteolytic ->
Mixed ->
Osteosclerotic
Pain, chalkstick fracture,
Tumours : benign / or Sarcoma - 5% of patients with severe disease
North of England, NZ and Australia
General pathology affecting bone
Infection
Tumours