18.1 Skeletal System Flashcards
Achondroplasia
Impaired cartilage proliferation in the growth plate
What is the mutation associated with achondroplasia?
FGFR3 - autosomal dominant activating mutation
What are the features of achondroplasia?
Short extremities with normal sized head and chest - mental function, life span and fertility are unaffected
Endochondral Bone Formation
Formation of a cartilage matrix then replaced by bone - long bones
Intramembranous Bone Formation
Formation of bone without a cartilage matrix - skull and chest
Osteogenesis Imperfecta
Congenital defect of bone formation that results in weak bone
What is the cause of osteogenesis imperfecta?
Autosomal dominant mutation in collagen I synthesis
Why do sclera appear blue in osteogenesis imperfecta?
Due to exposure of the choroidal veins
Osteopetrosis
Inherited defect of bone resorption that leads to thick and heavy bone
What is the most common mutation in osteoporosis?
Carbonic anhydrase II mutation that results in lack of acidic environment needed for bone resorption - osteoclasts cannot generate acidic enviroment
What are the clinical features of osteopetrosis?
- Fractures
- Anemia/Leukopenia
- Renal Tubular Acidosis
What is the treatment for osteopetrosis?
Bone Marrow Transplant
Rickets/Osteomalacia
Defective mineralization of osteoid due to low levels of Vitamin D
Rickets
Low Vitamin D in children causing pigeon breast with frontal bossing and bowing of legs
Osteomalacia
Low Vitamin D in adults that results in a weak bone with increased risk for fracture
What will be elevated in osteomalacia?
- PTH
- Alkaline Phosphatase
What environment is required to add Ca2+ to bone?
Alkaline
Osteoporosis
Loss of bone mass leading to porous bone mass increasing fracture risk
What are the serum value changes in osteoporosis?
They are all normal
Paget Disease of Bone
Imbalance of the osteoblasts and osteoclasts leading to too much resorption of the bone initially followed by osteoblast action
Does Paget Disease of Bone involve the whole skeleton?
No
What are the clinical features of Paget Disease of Bone?
- Bone pain
- Increasing hat size
- Lion-like face
- Elevated alkaline phosphatase
What is the treatment for Paget Disease of Bone?
- Calcitonin
- Bisphosphonates
Osteomyelitis
Infection of marrow space and bone often in children - commonly bacterial
What part of the bone is seeded with osteomyelitis in children?
Metaphysis
What part of the bone is seeded with osteomyelitis in adults?
Epiphysis
What is the most common cause of osteomyelitis?
S. aureus
Avascular Aseptic Necrosis
Ischemic necrosis of the bone and bone marrow
