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Musculoskeletal (Den 303 IHD) > Disease of bones and joints > Flashcards

Disease of bones and joints Flashcards

1
Q

Normal bone

A

Outer solid cortical bone
Inner trabecular (spongy) bone
Outer surface – periosteum
Inner space (medulla) contains fat or haemopoietic marrow

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2
Q

Constituents

A

Inorganic - 65%

Organic - 35%

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3
Q

Functions

A 
Mineral homeostasis
Houses haemopoietic system
-i.e. the bone marrow
Mechanical
-not a static scaffold - constantly remodelled
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4
Q

Bone diseases

A

Same stuff that can affect any other organ
-infections
-tumours
-trauma / degeneration
But also :
-specific derangements of bone’s particular specialised processes and function

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5
Q

Specific bone diseases

A

Disorders of matrix formation
Disorders of mineralisation
Disorders of bone turnover

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6
Q

The bone remodelling cycle - the key to understanding bone disease

A 
Activation of osteoclasts
Resorption of bone
Death of osteoclasts
Formation of new matrix by osteoblasts
Mineralisation of new matrix
Quiescence
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7
Q

The “Basic Multicellular Unit”

A

Cartilage
Osteoblasts
Osteoclasts
Bone

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8
Q

The concept of “coupling” of bone remodelling

A

Osteoblast activity - bone formation
Osteoclast activity - bone resorption
This coupling of bone formation and bone resorption is in normally in balance, except where a local imbalance is required for the purposes of growth
Coupling is lost in osteoporosis, resulting in a loss of bone volume

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9
Q

So what can go wrong with bone?

A

Defective matrix / matrix formation
Mineralisation problems
Turnover problems

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10
Q

Bone matrix formation diseases - rare

A 
Mutations in collagen
-type 1 in particular in bone
-->osteogenesis imperfecta
-->also affects ears / eyes / skin / teeth
Other abnormalities of bone matrix
-mucopolysaccharidoses
-->Morquio syndrome
-->Hurler syndrome
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11
Q

Cartilage matrix formation disorders - uncommon

A

e.g. Achondroplasia
-autosomal dominant
Failure of cartilage maturation at the growth plate
Caused by a mutation of fibroblast growth receptor receptor 3 which causes it to be continually activated (it is a negative regulator of bone growth)

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12
Q

Diseases of mineralisation - uncommon

A

Osteomalacia / Ricketts

  • caused by deficiency in vitamin D or calcium
  • can be dietary or metabolic
  • failure to mineralise ->cartilage overgrowth, failure of longitudinal growth
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13
Q

Bone remodelling problems

A 
The big one is : OSTEOPOROSIS
> porosity of bone due to a reduction in bone mass
-age
-hormonal influences (sex steroids)
-lifestyle (smoking, alcohol)
-activity
-genetics (Vit D receptor polymorphisms)
-nutrition (including malabsorption)
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14
Q

Osteoporosis - how it happens

A

“Uncoupling” of bone resorption and formation
-too much bone resorption
-too little bone formation
Loss of trabecular then cortical bone

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15
Q

Osteoporosis - complications

A 
Fragility fractures (vertebrae, femoral neck, distal radius)
Kyphosis (dowager’s hump)
Loss of height
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16
Q

Osteoporosis - treatment

A

Inhibit bone resorption (bisphosphonates)

Increase bone formation (experimental treatments)

17
Q

Disorders of abnormal turnover: Paget’s disease

A

Aka Osteitis Deformans
Excess turnover - “Collage of matrix madness” (!)
Once thought to hafve a viral cause (paramyxovirus) – link to dog ownership in Lancashire
More recent evidence suggests it is genetic

18
Q

General pathology affecting bone

A

Infection

Tumours

19
Q

Bone infections

A 
Osteomyelitis
-complication of compound fractures
-also blood borne
-necrosis of bone fragments
-new bone formation
Sinuses drain pus
Main organisms: S. aureus, M. tuberculosis
20
Q

Tumours

A

Most tumours in bone are metastases

  • lung
  • breast
  • prostate
  • thyroid
  • kidney
  • myeloma
21
Q

Primary bone tumours

A

Many are benign

Malignant ones are potentially rapidly fatal

22
Q

Chondrogenic

A 
60% benign
-osteochondroma (many sites)
-chondroma (mainly fingers)
40% malignant
Chondrosarcoma (femur, pelvis, skull base)
23
Q

Osteogenic

A

13% benign
-osteoid osteoma (any site, small tumours in cortex)
-osteoblastoma (larger tumours, typically spinal)
87% malignant
-osteosarcoma (most commonly distal femur)

24
Q

Malignant bone tumours

A

Osteosarcoma
Chondrosarcoma
Ewing’s sarcoma
Undifferentiated sarcoma

25
Q

Malignancies by age/ site

A

Osteosarcoma: 15-20, metaphyses, most commonly knee (6-%)
Chondrosarcoma: middle aged/ elderly, pelvis, ribs, proximal long bones
Ewing’s sarcoma: <20, diaphyses
Undifferentiated sarcoma: middle aged/ elderly, mainly metaphyses

26
Q

Joint diseases

A 
Infections
Crystal arthropathies
Chronic inflammatory arthritis
Osteoarthritis
Tumours – these are rare so don’t worry about them
27
Q

Joint infections

A

Septic arthritis

  • can be very trivial causes
  • insect bites / small cuts near joints
  • ->punching people in teeth
  • very painful
  • IV antibiotics +/- drainage
28
Q

Crystal arthropathies

A 
Gout
-urate crystals 2nd-ry to raised serum uric acid 
Pseudogout
-calcium pyrophosphate crystals
-age related
29
Q

Chronic inflammatory arthritis

A

Generally autoimmune
Rheumatoid arthritis is the commonest form
There are a variety of other types
-HLA B27-associated diseases such as ankylosing spondylitis and psoriatic arthritis
-systemic lupus and related conditions

30
Q

Rheumatoid arthritis

A 
Part of rheumatoid disease
Systemic inflammatory disorder
Auto-antibodies to immunoglobulins
-rheumatoid factor
-these are more of a marker of loss of immune self-tolerance than the cause of the disease
31
Q

Osteoarthritis/ osteoarthrosis

A 
Common
Degenerative disease
Erosion of cartilage
-minimal inflammation
-leads to changes in underlying bone
Mechanical
Predisposed by previous joint damage e.g. inflammation, intra-articular fracture
32
Q

Features of osteoarthritis

A

Fragmentation of cartilage (‘fibrillation’)
Osteophyte formation (bony projection associated with the degeneration of cartilage at joints)
Cysts in underlying bone
Represents a final common pathway of joint failure
The only effective treatment is arthoplasty (surgical removal of the joint and replacement with a prosthesis)

33
Q

Rheumatoid arthritis mechanism

A

Inflammation of synovium
-lymphocytyes / plasma cells / macrophages
-‘pannus’ formation (inflamed fibrous tissue)
Multiple joints
Extra articular features
Joint destruction caused by a cascade of cytokines driven by tumour necrosis factor-alpha
Anti-TNF-alpha antibodies are an effective treatment of severe rheumatoid disease

Musculoskeletal (Den 303 IHD) (2 decks)

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