Describe how schwann cells form the myelin sheath and the neurilemma.

Schwann cells or neurilemma cells are the cells which form the myelin sheath around neuronal axons in the peripheral nervous system (PNS) only.

Neurilemma is the collective term used for cytoplasm and nuclei present around the myelin sheath which helps in the regeneration process of nerves.

A Schwann cell surrounds the axon, invaginate it and the plasmalemma of the Schwann cells joins and from a double membrane structure called mesaxon. This mesaxon starts wrapping the axon in spiral fashion and cytoplasm start condensing into the compact myelin sheath.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.