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.

  • Regeneration of Nerve Fibers

    • The growth of the sprouts are governed by chemotactic factors secreted from Schwann cells (neurolemmocytes).
    • Injury to the peripheral nervous system immediately elicits the migration of phagocytes, Schwann cells, and macrophages to the lesion site in order 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 re-growth.

  • 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.

  • Optic (II) Nerve

    • As a consequence, the fibers are covered with myelin produced by oligodendrocytes, rather than Schwann cells, which are found in the peripheral nervous system.

  • Specific T-Cell Roles

    • T helper cells assist the maturation of B cells and memory B cells while activating cytotoxic T cells and macrophages.
    • Differentiation into helper T cell subtypes occurs during clonal selection following T cell activation of naive T cells.
    • Cytotoxic T cells (TC cells, or CTLs) destroy virally infected cells and tumor cells, and are also cause much of the damage in in transplant rejection and autoimmune diseases.
    • Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells), which have different properties and release different cytokines.
    • Regulatory T cells (Treg cells), also known as suppressor T cells, are crucial for the maintenance of immunological tolerance.

  • Natural Killer Cells

    • Natural killer cells (NK cells) are cytotoxic lymphocyte critical to the innate immune system.
    • The role of NK cells is similar to that of cytotoxic T cells in the adaptive immune response.
    • NK cells provide rapid responses to virally infected cells and respond to tumor formation by destroying abnormal and infected cells.
    • NK cells use two cytolytic granule mediated apoptosis to destroy abnormal and infected cells.
    • Typically, immune cells detect major histocompatibility complex (MHC) presented on cell surfaces, triggering cytokine release and lysis or apoptosis in cells that do not express MHC I, or express much less of it than normal cells.