Are cranial and spinal nerves myelinated?

Myelinated nerve fibres are present in spinal and cranial nerves.

Why Schwann cells are absent in CNS?

Schwann cells are excluded from the CNS during development by the glial limiting membrane, an area of astrocytic specialisation present at the nerve root transitional zone, and at blood vessels in the neuropil. Extensive Schwann cell CNS myelination may have therapeutic significance in human myelin disease.

Does the Schwann cell produce myelin in the central or peripheral nervous system?

Schwann cell, also called neurilemma cell, any of the cells in the peripheral nervous system that produce the myelin sheath around neuronal axons. These cells are equivalent to a type of neuroglia called oligodendrocytes, which occur in the central nervous system.

Are Schwann cells present in Unmyelinated neurons?

Structure. Schwann cells are a variety of glial cells that keep peripheral nerve fibres (both myelinated and unmyelinated) alive.

Why is there no Neurilemma in the CNS?

In the central nervous system, axons are myelinated by oligodendrocytes, thus lack neurilemma. The myelin Blay Ambrose sheaths of oligodendrocytes do not have neurilemma because excess cytoplasm is directed centrally toward the oligodendrocyte cell body.

How does Schwann cells form myelin sheath?

Myelin is formed by Schwann cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS). Each Schwann cell forms a single myelin sheath around an axon. Myelin itself forms by the spiral wrapping around an axon of an enormously expanded glial plasma membrane that then compacts.

What is the difference between Schwann cells and oligodendrocytes?

Oligodendrocytes are the cells which create myelin sheath around the axons of central nervous system. Schwann Cells are the cells which create myelin sheath around the axons of peripheral nervous system. Oligodendrocytes’ main function is the insulation of the nerve axons in the central nervous system.