Bone, Joint, and Soft Tissue Pathology Flashcards
What is osteoid?
Unmineralized organic portion of bone
What is osteoid comprised of?
Type I collagen
GAGs
What is hydroxyapatite?
Inorganic minerals of bone
What makes up hydroxyapatite?
Calcium
Phosphorus
What does the RANKL pathway promote?
Osteoclast bone resorption
What is the RANKL pathway?
RANK ligand osteoblasts binds to the RANK receptor on osteoclasts to activate them by releasing NF-k(kappa)B
Where are osteoclasts typically found?
Cowships lacunae
What does the Wnt pathway promote?
Osteoblasts bone formation
What is osteoprotegrin?
Blocks the RANK ligand to decrease bone resorption
What occurs in the Wnt pathway?
WNT proteins are produced by osteoprogenitor cells, WNT binds to LR5 and LR6 on osteoblasts to release beta-catenin activating OPG and inhibiting the RANKL pathway
What is produced by osteocytes to inhibit the WNT pathway?
Sclerostin
What is a dysostosis?
Bone abnormality in a localized place
What is a dysplasia?
Bone abnormality affecting the entire skeleton
What are common dysostosis?
Aplasia
Supernumerary digit
Syndactyly/craniosynosteosis
What is aplasia?
Complete absence of bone or digit
What is Syndactyly/craniosynosteosis?
Abnormal fusion of bones
What is a common dysplasia?
Abnormal growth
What is an important structural protein in bone?
Collagen type I
What is an important enzyme in bone?
Carbonic anhydrase 2
What is osteogenesis imperfecta?
Genetic deficiencies in synthesis of collagen type I
What is the most common inherited disorder of CT?
Osteogenesis imperfecta
Clinical presentation of osteogenesis imperfecta?
Too little bone
Blue sclera
Hearing loss
Small misshapen blue-yellow teeth (decrease dentin)
What is osteopetrosis?
Marble bone disease; bones are brittle and break easily
What causes osteopetrosis?
Impaired function of osteoclasts due to defect in carbonic anhydrase 2 (pH too high)
What is osteopenia?
Bone mass 1-2.5 standard deviations from peak bone mass
What is osteoporosis?
Bone mass greater that 2.5 standard deviations from peak bone mass
What histologically unique about osteopenia/osteoporosis?
The bone is histologically normal it is just decreased in quantity
What characterizes Paget disease?
Increased but structurally weak bone due to Cancellous bone becoming dense bone; typically polyostotic
What are the three stages of Paget disease?
Osteolytic
Mixed osteoclastic-osteoblastic
Osteosclerotic (burnout/quiescent)
What is the difference between rickets and osteomalacia?
Rickets: childhood disorder
Osteomalacia: adult disorder
What causes rickets/osteomalacia?
Vitamin D deficiency or abnormal metabolism
What occurs in rickets?
Deposition of bone in growth plates is affected
What causes osteomalacia?
Undermineralized bone formation during remodeling
What hormone is elevated in hyperparathyroidism?
Parathyroid hormone
What does increased PTH do?
Increases the activity of osteoclasts
What are the clinical effects of hyperthyroidism?
Osteoporosis
Brown tumors
What causes brown tumors?
Bone loss -> Microfractures -> hemorrhage -> macrophages
Hemosiderin in bones
What is the general rule for bone tumors relating to age?
Bone tumors are more common in younger individuals but are mostly benign
If an older individual has a bone tumor it is more likely to be malignant
What is the most common primary malignant bone tumor?
Osteosarcoma
What is indicative of an aggressive tumor in X-rays?
Codman triangle
What is the appearance of Ewing Sarcoma when stained with H and E?
Nests of densely packed small round cells called Homer-Wright rosettes
What is Ewing Sarcoma?
Primitive malignant primary bone tumor typically found on diaphysis of long bones and flat bones of the pelvis
What is a synarthroses?
Solid joint immovable lacking space or synovial fluid
Why is osteoarthritis a misnomer?
There is no inflammation that takes place in it
What is eburnation?
“Polishing” of the bone head in a joint due to loss of cartilage
