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Explain the changes in cartilage with age.
- Normally, chondroitin 4-sulfate is the predominant form, with low levels of Keratin sulfate.
- With age, chondroitin 6-sulfate becomes the predominant form with increased levels of keratin sulfate.
Describe the role of synovial tissue and synovial fluid.
- Capsule: a joint pouch containing synovial fluid.
- Synovium: Tissue that lines the capsule and creates synovial fluid (2cc in each knee).
Compare normal, inflammatory, non inflammatory, and septic conditions of synovial fluid.
- Normal: 1-4 mL, clear to pale yellow, transparent, very high viscosity, few WBCs (mostly monocytes), glucose equal to serum. No crystals or cultures.
- Inflammatory conditions: increase volume, cloudy, yellow/green, opaque, low viscosity, low glucose, 10k-20k WBCs/mm3 (mostly neutrophils), positive in gout and CPPD crystals.
- Non Inflammatory conditions: Like normal conditions with increased volume, straw color, slightly lower viscosity (still high), and 500 WBCs/mm3.
- Septic: Like inflammatory conditions, but positive for cultures, and negative for crystals. Has 50k WBCs/mm3.
Describe the effect of aging on the intervertebral disk.
- Cell concentration and water content of the nucleus pulposus decrease, making it more dense and stiff.
- The anulus fibrosus inner portion increases with age, the fibrocartilage degenerates, and the outer lamellae become stiff.
Explain how ligament injuries are graded.
- Ligament injury always occurs from excessive tension, and dislocations always include ligament injury:
- Grade I: Pain, no instability
- Grade II: some torn fibers, minimal instability.
- Grade III: completely torn
Strong in tension, weak in compression (like a rope). Mechanical forces depend on the orientation of the force applied.
The ligaments form wavy patterns that will straighten out under low stiffness before stretching at high stiffness. (the non-linear portion of a stress curve where collagen fibers straighten out).
Compare osteoblasts, osteocytes, and osteoclasts, and how to recognize them in a slide.
- Osteoblasts will be along the surface. Osteoblasts become osteocytes after becoming trapped in a lacuna.
- Osteocytes will be in lacunas (white border).
- Osteoclasts will be large multinucleated cells that descended from monocytes.
Identify the regional zones and describe the function of these zones in epiphyseal cartilage and their role in bone formation
- The epiphyseal plate has many zones.
- Zone 1: Resting cartilage (epiphyseal end)
- Zone 2: Proliferating cartilage (look for stacked coins)
- Zone 3: Hypertrophic cartilage. (bigger cells)
- Zone 4: Calcified cartilage.
- Zone 5: Zone of ossification (diaphyseal end, near the bone marrow)