Schwann cells

(noun)

The principal glia of the PNS, these cells are involved in the conduction of nervous impulses along axons, nerve development and regeneration, trophic support for neurons, production of the nerve extracellular matrix, modulation of neuromuscular synaptic activity, and presentation of antigens to T-lymphocytes.

Related Terms

Examples of Schwann cells 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.