Medullary sheath

Medullary sheath
Medullary Med"ul*la*ry, a. [L. medullaris, fr. medulla marrow: cf. F. m['e]dullaire.] 1. (Anat.) (a) Pertaining to, consisting of, or resembling, marrow or medulla. (b) Pertaining to the medula oblongata. [1913 Webster]

2. (Bot.) Filled with spongy pith; pithy. [1913 Webster]

{Medullary groove} (Anat.), a groove, in the epiblast of the vertebrate blastoderm, the edges of which unite, making a tube (the medullary canal) from which the brain and spinal cord are developed.

{Medullary rays} (Bot.), the rays of cellular tissue seen in a transverse section of exogenous wood, which pass from the pith to the bark.

{Medullary sheath} (Anat.), the layer of white semifluid substance (myelin), between the primitive sheath and axis cylinder of a medullated nerve fiber. [1913 Webster]


The Collaborative International Dictionary of English. 2000.

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  • Medullary sheath — Sheath Sheath, n. [OE. schethe, AS. sc[=ae][eth], sce[ a][eth], sc[=e][eth]; akin to OS. sk[=e][eth]ia, D. scheede, G. scheide, OHG. sceida, Sw. skida, Dan. skede, Icel. skei[eth]ir, pl., and to E. shed, v.t., originally meaning, to separate, to… …   The Collaborative International Dictionary of English

  • medullary sheath — n MYELIN SHEATH * * * myelin s …   Medical dictionary

  • medullary sheath — n. 1. Anat. a layer of myelin forming a sheath around certain nerve fibers 2. Bot. a ring of primary xylem around the pith of some stems …   English World dictionary

  • medullary sheath — noun a layer of myelin encasing (and insulating) the axons of medullated nerve fibers • Syn: ↑myelin sheath • Hypernyms: ↑sheath, ↑case • Part Holonyms: ↑medullated nerve fiber, ↑ …   Useful english dictionary

  • medullary sheath — med′ullary sheath′ n. 1) bot a narrow zone made up of the innermost layer of woody tissue immediately surrounding the pith in plants 2) anat. myelin sheath • Etymology: 1840–50 …   From formal English to slang

  • medullary sheath — noun Date: circa 1846 myelin sheath …   New Collegiate Dictionary

  • medullary sheath — 1. Bot. a narrow zone made up of the innermost layer of woody tissue immediately surrounding the pith in plants. 2. Anat. See myelin sheath. [1840 50] * * * …   Universalium

  • medullary sheath — /məˈdʌləri ʃiθ/ (say muh duluhree sheeth) noun 1. a narrow zone made up of the innermost layer of woody tissue immediately surrounding the pith in plants. 2. → myelin …  

  • Sheath — Sheath, n. [OE. schethe, AS. sc[=ae][eth], sce[ a][eth], sc[=e][eth]; akin to OS. sk[=e][eth]ia, D. scheede, G. scheide, OHG. sceida, Sw. skida, Dan. skede, Icel. skei[eth]ir, pl., and to E. shed, v.t., originally meaning, to separate, to part.… …   The Collaborative International Dictionary of English

  • Sheath knife — Sheath Sheath, n. [OE. schethe, AS. sc[=ae][eth], sce[ a][eth], sc[=e][eth]; akin to OS. sk[=e][eth]ia, D. scheede, G. scheide, OHG. sceida, Sw. skida, Dan. skede, Icel. skei[eth]ir, pl., and to E. shed, v.t., originally meaning, to separate, to… …   The Collaborative International Dictionary of English

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