Bone Pathology

Question 1

What is long bone made up of?

Answer 1

cortical or compact bone 
  (porosity ~ 15%)
  periosteum
      outer cortical membrane
  endosteum
      inner cortical membrane

trabecular, cancellous,
or spongy, bone
(porosity ~70%)

Question 2

What are the parts of long bones?

Answer 2

Epiphysis - proximal and distal ends of a long bone
Epiphyseal plate - cartilage separating metaphysis from epiphysis
Metaphysis - either end of diaphysis, filled with trabecular bone
Diaphysis - shaft of bone

Question 3

What is longitudinal bone growth?

Answer 3

• Occurs at the epiphyseal or “growth “ plate
• Bone cells are produced on the diaphyseal side of the plate
• Plate ossifies around age 18-25 and longitudinal growth stops

Question 4

What is circumferential bone growth?

Answer 4

• Growth throughout the lifespan
• Bone cells are produced on the internal layer of the periosteum by osteoblasts
• Concurrently bone is resorbed around the circumference of the medullary cavity by osteoclasts

Question 5

What is Wolff’s Law?

Answer 5

• Bone is laid down where needed and resorbed where not needed
• Shape of bone reflects its function
• • Osteoclasts resorb or take-up bone
• • Osteoblasts lay down new bone

Question 6

What is osteoarthritis?

Answer 6

Osteoarthritis (OA), or degenerative joint disease, is one of the oldest and most common types of arthritis, characterized by the breakdown of the joint’s cartilage. Cartilage breakdown causes pain and joint swelling. With time, there will be limited joint movement.

Question 7

What is rheumatoid arthritis?

Answer 7

A systemic disease that affects the entire body, characterised by the inflammation of the membrane lining the joint, which causes pain, warmth, redness and swelling.
The inflamed joint lining, the synovium, can invade and damage bone and cartilage, and inflammatory cells release enzymes that may digest bone and cartilage.