Amanda brosnan

Question 1

Classify nerve injury and differentiate between them

Answer 1

Neurapraxia - Grade 1 (compression)
-> Conduction block due to local demyelination
-> Axon, and connective tissues in tact
-> recovery in 6-8weeks
-> does not require wallerian degeneration
-> motor supply more affect than sensory
-> Blunt blows, compression, transient ischemia.

Axonotmesis -Grade 2 (contusion/crush)
-> Axon + myelin sheath discontinuity
-> all connective tissue in tact
-> wallerian degeneration.
-> loss of sensory and motor
-> several weeks recovery
-> proximal lesion growth 2-3mm/day
-> Distal lesion growth 1.5mm/day

Neurotmesis
Grade 3
-> Loss of axon, myelin and endoneurium continuity
Grade 4
-> Perineurium affected
Grade 5
-> all layers including epineurium affected
*recovery requires surgery- 1-2mm/day after sx

Question 2

Outline wallerian degeneration

Answer 2

first 24 hours:
(1) axon degeneration
(2) Schwann cells catabolise myelin
(3) macrophages will begin to phagocytose debris
(5) Growth factor release from schwann cells
(6) Axonal sprouting from proximal terminal end
-> 1-3mm a day of growth depending on severity of lesion
-> Muscle begins to under go denervation atrophy - cell shrinkage, resorption of myofibrils and contractile proteins.
(7) Basement membrane tubes guide sprouts to muscle for re-inervation
(8) Re-myelination by schwann cells - thinner myelin/shorter internodes

Question 3

3 indications for surgery following nerve damage

Answer 3

(1) Compression / Osteophyte formation
(2) No signs of recovery after 3-4 m of conservative management
(3) No evidence of recovery on EMG by 3-6 m

Question 4

What nerve is commonly used to grafting of brachial plexus nerves?

Answer 4

Sural nerve from posterior compartment of lower limb near ankle

Question 4

from what embryological layer does cartilage come from?

Answer 4

Mesoderm -> mesenchymal cells

Question 5

Describe hyaline cartilage and 4 places where it is found

Answer 5

(1) Extracellular matrix
- Intracellular water (65%)
- Collagen (15%) - Type 1 mostly
- Glycosaminoglycans (10%)
- Glycoproteins (5%)

(2) Chondrocytes
-> arranged in lacunae forming isogenous groups
-> surrounded by 3 layers of ECM: Capsular matrix, territorial, inter-territorial.

(3) Perichondrium
-> fibrous outer layer
-> inner chondrogenic layer - containing chondroblasts which secrete cartilage around themselves contributing to thickness of cartilage.
-> perichondrium does not surround hyaline cartilage of joints.

(4) GAG’s
-> contribute to cartilage growth and strength
-> GAG’s affected by hormone levels
*accelerators = testosterone, thyroxine, growth hormone (promotes somatomedin C in liver which contributes to cartilage growth)
*depressors = oestradiol, hydrocortisone

Found in
(1) Epiphyseal growth plate.
(2) trachea
(3) bronchi
(4) larynx