Wallarian degeneration is seen in –
Correct Answer: Distal to injury
Description: Ans. is 'a- i.e., Distal to injuryo Part distal to the injury - Wallarian degeneration or secondary degeneration,o Part proximal to the injury - Primary degeneration or retrograde degeneration.Degeneration of the distal part (Antegrade)Degeneration of proximal part (Retrograde)Stage of regenerationo Degeneration of distal part (distal to cut) is called Wallerian degeneration.o Within 24 hours histological and chemical changes occur.o The axon cylinder swells up and breaks down into small rodlets.o Myelin sheath breaks down into oily droplets, It occurs 8-32 days after injury.o Cells of the sheath of Schwann-divide mitotically and form cords of cells lying within the endoneurial tube (neurilemma) - macrophages remove the degenerating myelin and axis cylinder - thus schwann cell cytoplasm gradually fills the neurilemma, this process is completed by 3 months.o Hollow tube of neurilemma remains Intact and known as ghost tube.o Same as distal generation but unto nearest node of ranvier (nearest collateral),o Changes in the cell body:# Within 48 hours of injury the nissl grannies begins to disintegrate (known as chromatolysis).# Golgi apparatus fragments.# Cells swell.# Neurofibril disappear and nucleus displaced to cell margin.o Axis cylinders from stumps grows and sprout out (pseudopod like structure of fibril).o After 2-3 weeks peripheral endoneural tube, contian varying number of developing fibril.oMedullary sheath begins to develop in about 15 days and completed within one year.o Repair of cell body (i.e. Nissl granules and golgi apparatus) - begins about 20 days after nerve section and is completed in 80 days.1st change in cut nerve is - Axonal degeneration2nd change in cut nerv e is - Myelin degeneration
Category:
Physiology
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