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a tubular case or envelope.
arachnoid sheath the delicate membrane between the pial sheath and the dural sheath of the optic nerve.
carotid sheath a portion of the cervical fascia enclosing the carotid artery, internal jugular vein, vagus nerve, and sympathetic nerves supplying the head.
connective tissue sheath of Key and Retzius endoneurium.
crural sheath femoral sheath.
dural sheath the external investment of the optic nerve.
femoral sheath the fascial sheath of the femoral vessels.
Henle's sheath endoneurium.
lamellar sheath the perineurium.
medullary sheath myelin sheath.
myelin sheath (nerve sheath) the sheath surrounding the axon of myelinated nerve cells, consisting of concentric layers of myelin formed in the peripheral nervous system by the plasma membrane of Schwann cells, and in the central nervous system by the plasma membrane of oligodendrocytes. It is interrupted at intervals along the length of the axon by gaps known as nodes of Ranvier. Myelin is an electrical insulator that serves to speed the conduction of nerve impulses (see saltatory conduction).
pial sheath the innermost of the three sheaths of the optic nerve.
root sheath the epidermic layer of a hair follicle.
sheath of Schwann neurilemma.
synovial sheath synovial membrane lining the cavity of a bone through which a tendon moves.
tendon sheath a lubricated fibrous or synovial layer of tissue in which the tendon is housed and through which it moves.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Improper laying down or breakdown of a myelin sheath of a nerve fiber, caused by abnormal myelin metabolism.
Farlex Partner Medical Dictionary © Farlex 2012


Improper laying down or breakdown of a myelin sheath of a nerve fiber, caused by abnormal myelin metabolism.
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
Dysmyelination (abnormal formation or production) and demyelination (breakdown or loss) can lead to abnormal neurodevelopment and/or degeneration, loss of neurodevelopmental milestones, seizures, and movement disorders.
(17) These late-occurring white matter abnormalities are presumed to be the result of secondary demyelination following cortical neuronal death and axonal deterioration, rather than from primary dysmyelination. (13,20,22) However, a combination of delayed myelination and demyelination (11,17) has also been proposed.
Shi mice have extensive dysmyelination due to deletions in the gene encoding MBP.
These mice give a form by which we can begin to recognize the early onset dysmyelination seen in patients with R98C and alike mutations.29
Ghandour, "Astrocytic hypertrophy in dysmyelination influences the diffusion anisotropy of white matter," Journal of Neuroscience Research, vol.