medullary sheath

sheath (shēth) a tubular case or envelope.

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arachnoid sheath  the continuation of the arachnoidea mater around the optic nerve, forming part of its internal sheath.

carotid sheath  a portion of the cervical fascia enclosing the carotid artery, the internal jugular vein, and the vagus nerve.

crural sheath  femoral s.

dentinal sheath  the layer of tissue forming the wall of a dentinal tubule.

dural sheath  the external investment of the optic nerve.

femoral sheath  the investing fascia of the proximal portion of the femoral vessels.

sheath of Henle  endoneurium.

Hertwig sheath  root s. (1).

sheath of Key and Retzius  endoneurium.

lamellar sheath  the perineurium.

Mauthner's sheath  axolemma.

medullary sheath , myelin 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 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.

pial sheath  the continuation of the pia mater around the optic nerve, forming part of its internal sheath.

root sheath 

1. an investment of epithelial cells around the unerupted tooth and inside the dental follicle.

2. the epithelial portion 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  epitendineum.

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medullary sheath

n.

See myelin sheath.

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sheath [shēth]

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.