medullary rays

1 definition found

medullary rays - Collaborative International Dictionary of English v.0.48 :

  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]