Bone Pathology I Flashcards
What type of tissue is bone?
Connective tissue
What is the inorganic component of bone?
Hydroxyapatite
What is the organic component of bone?
Cells, protein, type I collagen
What is unmineralized bone called?
Osteoid
What is endochondral bone formation and which bones are made this way?
Mineralized bone is laid on top of a cartilage matrix
Most bones (long bones) are formed this way
What is intramembranous bone formation and which bones are formed this way?
Formation of the bone without preexisting cartilage matrix. Bone formation occurs within membrane-like mesenchymal condensations
Flat bones (skull, rib cage, mandible) are made this way
Fractured bones repair themselves via what process?
Callus formation
What is a pathologic fracture?
Bone that breaks due to an underlying disease process (non-traumatic)
What is osteoporosis?
Absolute decrease in bone mass
Leads to increased risk of fracture
What causes localized osteoporosis?
Disuse
What are the two types of primary osteoporosis?
Post-menopausal
Senile (in men)
How does bone remodeling lead to osteoporosis?
As we age, osteoclast activity > osteoblast activity
What cells are responsible for activating osteoclasts?
Surface osteoblasts
RANK receptors are located on what type of cell?
Osteoclasts
RANK signaling activates what?
NFkappaB –> important for osteoclast generation and survival
RANK ligand is on which cell?
Osteoblasts
What is the mechanism by which osteoblasts inhibit activation of osteoclasts?
Production of OPG
OPG binds to RANK ligand and inhibits interaction with the RANK receptor on osteclasts
How are RANK and RANKL affected by menopause?
Increase expression of both RANK and RANKL in menopause contributes to osteoporosis (through increased activation of osteoclasts)
Which bones are more inclined to fracture?
Vertebra, wrist, ribs, pelvis
What is the etiology of rickets/osteomalacia?
Vitamin D deficiency –> bone mineralization defect and accumulation of osteoid (unmineralized bone)
How does vitamin D affect calcium absorption?
Vitamin D increase calcium and phosphate absorption from the gut
What is osteomalacia?
Lack of vitamin D in adults
Loss of bone density (osteopenia)–> fractures and microfractures, bone pain
What happens to the bones of children with Ricketts?
The growth plate is not adequately mineralized –> osteoclasts do not absorb the growth plate cartilage and you end up with excess cartilage and lack of mineralized bones.
How do joints of children with rickets appear?
Knobby/enlarged- due to lack of absorption of cartilage.
What causes primary hyperparathyroidism?
Adenoma
Hyperplasia
Carcinoma
What causes secondary hyperparathyroidism?
Prolonged hypocalcemia
What is a brown tumor?
With hyperparathyroidism, increase Ca resorption from bone –> microfractures
Microfractures cause hemorrhage in the bone, which recruits macrophages and results in extensive repair with ingrowth of fibrous tissue
Why is advanced hyperparathyroidism rarely seen these days?
Calcium levels are checked when you order an BMP
What is Paget’s disease of the bone?
Disease caused by osteoclast dysfunction- excessive bone resorption followed by disorganized, excessive bone formation
What is the pattern of bone seen in Paget’s disease of the bone?
“Mosaic pattern” of bone- with “cement lines” in between bones
What is the risk associated with high vascularity of bones?
High output heart failure- shunting of blood to hypervascular areas
What is the most dreaded complication of paget’s disease of the bone?
Osteosarcoma
Fibrosarcoma
5-10% of patients
What is the treatment for Paget’s disease of the bone?
NSAIDS for pain
Inhibitors of osteoclast function (bisphosphonates, calcitonin)
What blood serum finding may be seen in someone with Paget’s disease?
Elevated alkaline phosphatase
other causes- obstructive liver disease
