Bone disease: causes of wear

sophietevans
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Created by sophietevans over 7 years ago
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From part 2 of the 26/11/13 Human Physiology lecture on bone structure and disease

Resource summary

Question Answer
What is the most common form of arthritis? OSTEOARTHRITIS.
What type of wear is caused by two of the same thing rubbing against one another? Attrition.
What type of wear is a result of two different things rubbing against each other? Abrasion.
What type of wear is involved in osteoarthritis? Attrition
What type of wear is involved in rheumatoid arthritis, in which bone rubs against inflamed cartilage? Abrasion
What is an osteophyte? A bony 'spur' or outgrowth produced in an attempt to repair bone worn in arthritis. These can rub against tendons and muscles and cause pain.
What predisposes to attrition between two bones? Reduction in hyaline cartilage.
List some risk factors for osteoarthritis. Injury to the cartilage (this could be in compensation for a different injury, e.g. favouring a non-injured leg), congenital defects causing postural changes, or muscle atrophy or impairment. Further, it can occur secondary to associated conditions that affect cartilage, e.g. rheumatoid arthritis.
What is rheumatoid arthritis? It is the inflammatory cause of cartilage degradation, resulting in inflammation of the synovial membrane (synovitis).
Name an inflammatory mediator which can increase osteoclastic activity. TNF-α
What type of disease is rheumatoid arthritis? Autoimmune
What are matrix metalloproteinases and how are they involved in the development of rheumatoid arthritis? Matrix metalloproteinases are enzymes which can degrade all components of the extracellular matrix. Their production is stimulated by inflammatory mediators such as IL1-β and TNF-α. MMP-1 is produced by the synovial cells lining joints and breaks down type 2 collagen; MMP-13 is a product of resident chondrocytes in the cartilage and breaks down type 2 collagen. MMPs 2, 3, and 9 are also involved and can break down non-collagen matrix components.
What is pannus formation with regard to rheumatoid arthritis? The formation of granulation tissue as a result of the inflammatory response.
Other than pannus formation, what are some other complications of/features of rheumatoid arthritis? Fibrosis and bone and cartilage erosion. The latter can lead to osteoarthritis.
Given that it is an inflammatory disease with no cure, what type of condition is rheumatoid arthritis? Both chronic and progressive.
What three types of mediators are involved in the pathogenesis of rheumatoid arthritis? Cytokines, prostanoids, and proteolytic enzymes.
Name two pro-inflammatory cytokines that are central mediators in the pathogenesis of rheumatoid arthritis. IL1-beta and TNF-alpha.
In osteoarthritis, mechanical stress is placed on joints. Give three possible reasons for this. Injury, excessive weight, or excessive exercise.
In osteoarthritis there is an overexpression of matrix degrading proteins, including: Collagenases (1, 8, 13), gelatinase (2, 9), and stromelysins (3, 10, 11).
What is endochondral ossification? A type of bone growth that occurs in long and short bones, and results from the replacement of cartilage with bone along epiphyseal growth plates.
What is subchondral bone? Bone that is directly beneath the calcified cartilage, above the epiphyseal plate and above the majority of the bone in the epiphysis.
When does cartilaginous injury become a problem for subchondral bone? When the articular and calcified cartilage have been abraded away, the subchondral bone is at risk because it is weaker.
What is a chondral defect? The articular and calcified cartilage have been worn away, and subchondral bone is exposed to damage.
What is an osteochondral defect? Both articular and calcified cartilage have been worn away, and the subchondral bone is exposed and damaged too, leaving the trabecular bone beneath it exposed and likely damaged.
What is osteochondritis dessicans? Vascular occlusion in the subchondral bone results in necrosis of the bone tissue, which increases osteoclastic activity. This leaves cartilage without an adequate support structure beneath it, which predisposes to cracks forming in the joints and fragmentation and further damage may occur.
What is osteomyelitis? Infection and inflammation of the bone and/or bone marrow.
How might osteomyelitis be caused? A pathogen may travel to the bone through the bloodstream, or may be introduced as a result of trauma, be this accidental (e.g. breaking a bone) or iatrogenic (e.g. a hip replacement).
What is a common name for osteogenesis imperfecta? Brittle bone disease.
What type of disease is osteogenesis imperfecta? Genetic
What is characteristic about osteogenesis imperfecta? Defective or absent connective tissue in the bones.
There are four major types of osteogenesis imperfecta. What are these? I: mild severity. II: severe - often lethal perinatally. III: progressive and deforming. IV: deforming.
What is fibrous dysplasia? A chronic disorder in which the bone expands due to an increase in fibrous tissue in the medullary cavity. This is not a form of cancer.
What are three characteristics of fibrous dysplasia? Pain (due to the expansion of bone), brittle bones, and visible bone deformity.
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