What is the composition of myelin sheath?

Myelin is composed of about 40% water and the dry mass is composed of about 80% lipids and 20% protein. The mainly lipid composition of the myelin gives it a white hue, hence the reference to the brain’s “white matter.” The main lipid found in myelin is a glycolipid called galactocerebroside.

What is the myelin sheath made of Schwann cells?

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. In contrast, each oligodendrocyte forms multiple sheaths (up to 30 or more) around different axons (Figure 1).

How do Schwann cells make myelin?

The myelin lamella is formed by fusion of the apposed inner leaflets of the plasma membrane in glial cells, with no intervening cytoplasm (Figure 1B). Schwann cells make myelin in the peripheral nervous system (PNS: nerves) and oligodendrocytes in the central nervous system (CNS: brain and spinal cord).

Are Schwann cells the myelin sheath?

Schwann cell, also called neurilemma cell, any of the cells in the peripheral nervous system that produce the myelin sheath around neuronal axons. Schwann cells are named after German physiologist Theodor Schwann, who discovered them in the 19th century.

What is the sheath of the Schwann cell also called?

Neurilemma (also known as neurolemma, sheath of Schwann, or Schwann’s sheath) is the outermost nucleated cytoplasmic layer of Schwann cells (also called neurilemmocytes) that surrounds the axon of the neuron. It forms the outermost layer of the nerve fiber in the peripheral nervous system.

Where are Schwann cells located?

Schwann cells, or neurolemmocytes, discovered by Theodore Schwann , are glial cells found in the peripheral nervous system that wrap around the axon of a neuron multiple times until a myelin sheath is formed.

What two cells can form myelin sheaths?

Myelination is the formation of a myelin sheath. Myelin sheaths are made of myelin, and myelin is produced by different types of neuroglia: oligodendrocytes and Schwann cells, where oligodendrocytes myelinate axons in the central nervous system, and Schwann cells myelinate axons in the peripheral nervous system.

Do Schwann cells have a nucleus?

The nucleus of a Schwann’s cell is oval and contains one or two nucleoli. Masses of chromatin are found on the inner surface of the nuclear membrane. Mitochondria, lysosomes , the Golgi complex, microtubules , microfibrils, free ribosomes, and ribosomes attached to the membranes are concentrated around the nucleus in the cytoplasm.