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28 Cards in this Set

  • Front
  • Back
What are the epiphysis, diaphysis, and metaphysis?
Epiphysis: growth plate
Diaphysis: parallel cortices
Metaphysis: non-parallel cortices, adjacent to epiphysis
Where should woven bone never be found?
In adults
What is the pathophysiology of achondroplasia?
It is caused by a defect in cartilage formation impairing enchondral ossification. However, the flat bones formed by intramembranous processes like skull, sternum, and pelvis will be normal.
What is Wilt's law?
notion that bone will remodel itself based on the stress placed on it
What causes osteogenesis imperfecta?
This disease is caused by a failure of osteoblasts to normally synthesize collagen leading to a fragile skeleton.
What is a characteristic sign of osteogenesis imperfecta?
Blue sclerae due to collagen deficiency
Is the bone in osteogenesis imperfecta hypo or hypercellular?
The disease is caused by a lack of normal collagen production by osteoblasts. The bone's osteocytes become crowded as a result and the bone is actually HYPERcellular
What is osteoporosis?
increased porosity of the skeleton due to a reduction in bone mass, despite NORMAL mineralization
What are two causes of primary osteoporosis and two causes of secondary osteoporosis?
Primary: senile (age related) and postmenopausal osteoporosis
Secondary: endocrine disorders, neoplasia, GI factors, drugs, immobilization (reduced physical activity means there are fewer mechanical forces to stimulate normal bone remodeling)
What does menopause have to do with osteoporosis?
Postmenopausal women have low estrogen which caused IL1 to be produced by monocytes in the blood. This cytokine release increases osteoclastic activity
What is osteopetrosis?
A disorder of osteoclast dysfunction that causes diffuse skeletal sclerosis and counterintuitively brittle bones (...marrow is replaced by lots of poorly organized fragile woven bone)
What are some important complications of osteopetrosis?
pinching of optic nerve (blindness), overgrowth of bone in inner ear (deafness), cranial nerve palsy, hydrocephalus
By what age do people become skeletally mature?
age 20
What is Paget's disease (osteitis deformans)?
This is a disorder of osteoblast dysfunction leading to excessive resorption of normal bone followed by excessive new bone formation of haphazard arrangement
What causes Paget's disease?
Infection by paramyxovirus, a retrovirus, that reduces the secretion of IL6 which usually recruits osteoclasts
What labs might be expected in Paget's disease?
The excessive osteoblastic activity causes high serum alkaline phosphatase levels
What fatal complication of Paget's must be avoided?
Secondary sarcomas
What are the three stages of Paget's?
1.) initial osteolytic stage
2.) mixed osteolytic-osteoblastic stage
3.) osteosclerotic stage
How can you treat Paget's?
Calcitonin diphosphonates (counteracts PTH)
What is osteomalacia? How does it relate to rickets
metabolic defect of reduced vit D leading to increased UNmineralized bone, rickets is the childhood version
What conditions can lead to ischemia that causes avascular necrosis?
Steroid use, alcoholism, trauma, infection, sickle cell, lupus, RA, pressure dz of divers
What characteristic shape does the necrotic region have in avascular necrosis? In what type of infarct?
wedge shaped segment in subchondral infarct (tends to be geographic in medullary infarct)
What happens to the overlying cartilage in avascular necrosis?
It remains viable because it is receiving its nutrition from the synovial fluid.
What is the crescent sign of avascular necrosis?
It is the collapse of the articular surface due to weakened osteoclastic resorption at the margin of infarct. This causes the dead trabeculae to fracture beneath the subchondral plate.
What kind of cells will be seen in a bone affected by osteomyelitis?
It is a bone infection thus acute inflammatory cells - neutrophils!
What are common bacterial causes of osteomyelitis and their preferred infecting demographic?
Staph - most common
E. Coli, Klebsiella, Pseudomonas - pt with GU infxn, drug user
H. flu, Group B strep - neonatal pt
Salmonella - sickle cell pt
What is Pott's dz?
Tuberculous osteomyelitis in the vertebrae caused by hematogenous spread from an active site of Tb infxn
How does osteomyelitis present in syphilis?
Occurs in tertiary stage of acquired syphilitic disease, presents as saber shins (periosteal rxn of tibia) or saddle nose deformity