Pathology 2nd Year 6.13 Questions

What is enchondral and intramembranous ossification and where do they occur?

• Endochondral ossification: bone develops from cartilage, occurs in long bones (primary/secondary ossification centers, growth plate).

• Intramembranous ossification: bone develops directly from mesenchyme, occurs in flat bones (skull, clavicle)

What is bone remodeling and which cells are directly involved?

Continuous replacement of old bone.

Osteoclasts resorb, osteoblasts form bone.

Regulated by RANK/RANKL/OPG

Explain what is bone fracture.

Loss of bone integrity due to injury or reduced strength

What is the classification of bone fractures? Give examples.

Simple (transverse, oblique), Compound (open wound), Comminuted (fragmented), Displaced (misaligned), Greenstick (partial, children), Stress (repeated activity), Pathologic (weakened bone, tumor/inflammation)

Explain what is callus.

Temporary fibrocartilaginous and bony tissue around fracture, stabilizes bone, remodels to lamellar bone

Characterize stages of bone healing process.

Hematoma formation → Soft callus → Hard callus → Remodeling to lamellar bone

What factors may affect healing of bone fracture?

Displaced/comminuted fracture, poor immobilization, nonunion, infection, malnutrition, diabetes, skeletal dysplasia

What is osteonecrosis (avascular necrosis)?

Ischemic necrosis of bone/marrow due to reduced blood supply

Morphological features and significance of osteonecrosis?

Wedge-shaped pale necrosis, trabecular/marrow affected, cortex spared. Leads to bone pain, collapse, osteoarthritis

What is osteomyelitis?

Inflammation of bone and marrow

Causative factors of osteomyelitis?

Pyogenic bacteria (Staph aureus), Mycobacteria, other microbes. Routes: hematogenous, contiguous spread, direct implantation

Morphological features of pyogenic osteomyelitis (acute vs chronic).

Acute: necrosis, neutrophils, abscess, sequestrum. Chronic: bone resorption, fibrosis, involucrum, lymphocytes

Complications of osteomyelitis?

Pathologic fracture, AA amyloidosis, endocarditis, sepsis, rare: sarcoma, SCC in sinus tracts

What is osteoporosis?

Reduced bone mass, fracture risk

Which bones are affected in osteoporosis?

Whole skeleton, mainly vertebral bodies

Causative factors and morphological features of osteoporosis?

Primary (postmenopausal ↑osteoclast, senile ↓osteoblast), secondary (endocrine, GI, drugs). Thin trabeculae, vertebral collapse, kyphosis

What is rickets?

Skeletal disease from vitamin D deficiency in children

Causative factors of rickets?

Dietary D/Ca deficiency, low sunlight, poor maternal milk, renal disorders, malabsorption

Pathogenesis of rickets?

Vit D deficiency → hypocalcemia → ↑PTH → bone resorption & phosphate loss → impaired mineralization → soft bones

Morphological features of rickets?

Microscopic: unmineralized osteoid, cartilage overgrowth. Macroscopic: craniotabes, frontal bossing, rachitic rosary, pigeon chest, Harrison groove, lordosis, bow legs

What is osteomalacia? Difference vs osteoporosis.

Osteomalacia: defective mineralization in adults (soft bones). Osteoporosis: bone loss but normal mineralization

Effect of ↑parathyroid activity on bone?

↑PTH → ↑osteoclasts → bone resorption → osteopenia, deformities, fractures

What is infective arthritis?

Joint inflammation due to infection

Morphological features of infective arthritis?

Usually one joint (knee, hip, shoulder). Purulent exudate in joint cavity

What is osteoarthritis? Classification?

Degenerative joint disease, cartilage degeneration. Primary (idiopathic, age). Secondary (injury, deformity, obesity, diabetes)

Pathogenesis of osteoarthritis?

Cartilage injury → failed repair → cytokines (TNF, IL-1) → chondrocyte death → cartilage loss, bone changes

Morphological features of osteoarthritis?

Cartilage loss, joint mice, bone eburnation, cysts, osteophytes, mild synovitis. Joints: hips, knees, spine, finger joints

What is rheumatoid arthritis? Which joints affected?

Autoimmune proliferative synovitis. Affects small joints (fingers, toes)

Pathogenesis of rheumatoid arthritis?

Autoimmunity (CD4 T, B, macrophages, cytokines) → pannus formation → cartilage/bone destruction, ankylosis

Morphological features of rheumatoid arthritis?

Symmetric small joints. Hyperplastic synovium, pannus, fibrosis, ankylosis, rheumatoid nodules

Differences between osteoarthritis and rheumatoid arthritis?

OA: degenerative, cartilage injury, osteophytes, mild synovitis. RA: autoimmune, pannus, ankylosis, nodules

What is primary and secondary gout?

Primary: genetic/idiopathic hyperuricemia. Secondary: other diseases (tumor lysis, CKD)

Pathogenesis of gout + immune cells?

Urate crystals → macrophages → IL-1β, cytokines → neutrophils → enzymes/ROS → inflammation, damage

Clinical morphological forms of gout?

Acute arthritis, chronic tophaceous arthritis, tophi, gouty nephropathy

Which structures are affected by gout?

Small joints (1st MTP), cartilage, tendons, kidneys

Morphological features of gout?

Macros: chalky tophi, deformity. Micros: urate crystals, neutrophils, pannus, fibrosis