WordNet
n. a sheet of vascular tissue separating the vascular bundles [syn: vascular ray]
Wikipedia
Medullary ray may refer to:
- Medullary ray (anatomy), the middle part of the Cortical lobule
- Medullary ray (botany), characteristic radial sheets or ribbons extending vertically, found in woods
Medullary ray is a cellular structure found in woods. In this context the term refers to radial sheets or ribbons extending vertically through the tree across and perpendicular to the growth rings. Also called pith rays or wood rays, these formations of primarily parenchyma cells allow the radial transport of sap and are essential in the process of tylosis. In quartersawn material, where the wood is cut into boards with the growth rings roughly perpendicular to the face of the board, the medullary rays often produce beautiful figure such as silver grain, medullary spots, pith flecks, etc.
In anatomy, the medullary ray (Ferrein's pyramid) is the middle part of the cortical lobule or renal lobule, consisting of a group of straight tubes connected to the collecting ducts.
Their name is potentially misleading — the "medullary" refers to their destination, not their location. They travel perpendicular to the capsule and extend from the cortex to the medulla.
Usage examples of "medullary ray".
Similar roots of Jasmine, especially those of Jasminum fruticans, are sometimes intermixed, and can be distinguished by the absence of indurated pith cells, which occur in Gelsemium, by the abundance of thin-walled starch cells in the pith and in the medullary ray cells (those of Gelsemium being thickwalled and destitute of starch), and by the bast fibres round the sieve tubes.
Just beside her the bark was deeply split, a huge crack reaching in to breach the medullary ray that carried die tree's necessary nutrients, and on, deep into the sapwood.