NAIMMCQ: Pathology

Outline the five steps involved in general wound healing

Answer:

A. removal of central core
B. formation of granulation tissue
C. extracellular matrix deposition
D. scar formation
E. wound contraction

What is healing of a long bone fracture?

Answer:

1. removeal of necrotic bone and debris by macrophages and osteoclasts
2. angiogenesis and fibroblast proliferation
3. callus formation: pluripotential mesenchymal cells from the soft tissue, periosteium and bone marrow proliferate and differentiate, composed of fibrous tissue, cartilage and bone, fusion of osteogenic layers on either side of the callus
4. remodeling phase: newly formed woven bone is gradually converted to lamellar bone, at about 8 weeks the callus is called a secondary or hard callus and it consists mainly of bone
5. stage of consolidation: endocondrial ossification of the cartilage continues, trabecular bone replaces cartilage, the new bone is continuously remodelled and eventually replaced by compact bone, dead bone removed before healing can be completed, eventually the oritinal line of the bone is restored (takes years)

What is the repair of peripheral nerves?

Answer:

1. schwann cells phagocytose degenerative myelin
2. proximal and distal axons degenerate
3. debris is cleared by macrophages
4. schwnn cells proliferate along the former course of the axon along endoneurium
5. proximal axon generates varies sprouts advancing between schwann cells
6. once regenerated axons meet end organ schwnn cells start myelin production

What is repair of skeletal muscle?

Answer:

skeletal muscle cells ar long multinucleated, permanent cells
myonuclei ar unable to divide
1. macrophages clean up intracelular debris
2. satellite cells, mitosis --> myoblasts --> migrate from marginal site to centre of myobibrils, new myofiber nuclei
3. intact basal lamina: keeps both satellite cells and their myoblast progeny within damaged segment, keeps fibroblasts out, allows entry and exit of macorphages
4. after critical mass of myoblasts have formed they begin to fuse to form myotubular giant cells
5. myotubes sent out numerous cytoplasmic processes of which re-establish contact with the original muscle cell
6. cell membranes fuse to facilitat union of regenerated segment with vable myofibre

What is repair of articular cartilage with injuries that involve subchondral bone?

Answer:

haemorrhage, inflammatory response
defects is filled with fibrovascular tissue
differentiation into chondrocytes starts after about two weeks, production of proteoglycans
fibrocartilage formed after 6-8 weeks

What is repair of articular cartilage with erosions, superficial defects?

Answer:

no haemorrhage or inflammation
no repair, lesions persist for long periods without progressing