Schwann cell

Examples of Schwann cell in the following topics:

• Neuroglia of the Peripheral Nervous System

  • The two kinds of glia cells in the PNS, schwann cells and satellite cells, each have unique functions.
  • The PNS has two kinds of neuroglia: schwann cells and satellite cells.
  • Schwann cells provide myelination to peripheral neurons.
  • Functionally, the schwann cells are similar to oligodendrocytes of the CNS.
  • Satellite cells are small glia that surround neurons' sensory ganglia in the ANS.

• Characteristics of Nervous Tissue

  • It consists of neurons and supporting cells called neuroglia.
  • The cell body is like a factory for the neuron.
  • In the peripheral nervous system, Schwann cells are neuroglia cells that support neuronal function by increasing the speed of  impulse propagation.
  • The Schwann cells are underlain by the medullary sheath.
  • The myelin layer (concentric) surrounds the axon of a neuron, showing Schwann cells.

• Types of Nervous Tissue

  • Neuroglia are also called "glial cells."
  • Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells and oligodendrocytes.
  • In the PNS, satellite cells and Schwann cells are the two kinds of neuroglia.
  • Satellite cells surround neuron cell bodies in the peripheral nervous system (PNS).
  • Schwann cells surround all nerve fibers in the peripheral nervous system and form myelin sheaths around the nerve fibers.

• Glia

  • This is distinctive from the PNS where a single Schwann cell provides myelin for only one axon as the entire Schwann cell surrounds the axon.
  • Glial cells support neurons and maintain their environment.
  • Glial cells of the (a) central nervous system include oligodendrocytes, astrocytes, ependymal cells, and microglial cells.
  • Microglia scavenge pathogens and dead cells.
  • Glial cells of the (b) peripheral nervous system include Schwann cells, which form the myelin sheath, and satellite cells, which provide nutrients and structural support to neurons.

• Regeneration of Nerve Fibers

  • The growth of the sprouts are governed by chemotactic factors secreted from Schwann cells (neurolemmocytes).
  • Injury to the PNS immediately elicits the migration of phagocytes, Schwann cells, and macrophages to the lesion site to clear away debris such as damaged tissue.
  • The proximal axons are able to regrow as long as the cell body is intact and they have made contact with the Schwann cells in the endoneurial channel.
  • During Wallerian degeneration, Schwann cells grow in ordered columns along the endoneurial tube.
  • Also, macrophages and Schwann cells release neurotrophic factors that enhance regrowth.

• Capacity of Different Tissues for Repair

  • Neuroregeneration refers to the regrowth or repair of nervous tissue, cells, or cell products.
  • Growth is governed by factors secreted from Schwann cells.
  • Injury to the peripheral nervous system immediately elicits the migration of phagocytes, Schwann cells, and macrophages.
  • The proximal axons are able to regrow as long as the cell body is intact,\ and they have made contact with the Schwann cells in the endoneurial channel.
  • In undamaged muscle, the majority of satellite cells are quiescent; they neither differentiate nor undergo cell division.

• Classification of Nerves

  • These occur when an unmyelinated Schwann cell bundles the axons close together by surrounding them.
  • The Schwann cell keeps them from touching each other by squeezing its cytoplasm between the axons.

• Clusters of Neuronal Cell Bodies

  • Ganglia are composed mainly of neuron cell bodies (somata) and dendritic structures.
  • Satellite glial cells are a type of glial cell that line the exterior surface of neurons in the peripheral nervous system (PNS) .
  • Satellite glial cells (SGCs) also surround neuron cell bodies within ganglia.
  • They are of a similar embryological origin to Schwann cells of the PNS, as they are both derived from the neural crest of the embryo during development.
  • Satellite cells also act as protective, cushioning cells.

• Introducing the Neuron

  • The brain is made up entirely of neurons and glial cells, which are non-neuronal cells that provide structure and support for the neurons.
  • The cell body contains a specialized structure, the axon hillock, which serves as a junction between the cell body and the axon.
  • Myelin is produced by glial cells (or simply glia, or "glue" in Greek), which are non-neuronal cells that provide support for the nervous system.
  • In the central nervous system, the glial cells that form the myelin sheath are called oligodendrocytes; in the peripheral nervous system, they are called Schwann cells.
  • The above image shows the basic structural components of an average neuron, including the dendrite, cell body, nucleus, Node of Ranvier, myelin sheath, Schwann cell, and axon terminal.

• Cell Theory

  • Cell theory states: living things are composed of one or more cells; the cell is the basic unit of life; cells arise from existing cells.
  • By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory.
  • The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.
  • Schleiden and Schwann proposed spontaneous generation as the method for cell origination, but spontaneous generation (also called abiogenesis) was later disproven.
  • "All cells only arise from pre-existing cells.