Decussation

Source: Wikipedia, the free encyclopedia.
Not to be confused with Desiccation, Chiasm (anatomy), or Commissure.
Section of the medulla oblongata at the level of the decussation of the pyramids

Decussation is used in biological contexts to describe a crossing (due to the shape of the

decussatio pyramidum
.

Similarly, the anatomical term chiasma is named after the Greek uppercase 'Χ' (chi). Whereas a decussation refers to a crossing within the central nervous system, various kinds of crossings in the peripheral nervous system are called chiasma.

Examples include:

  • In the
    decussation of pyramids and sensory decussation. In neuroanatomy, the term chiasma is reserved for crossing of- or within nerves such as in the optic chiasm
    .
  • In
    opposite pattern of leaves which has successive pairs at right angles to each other (i.e. rotated 90 degrees along the stem when viewed from above). In effect, successive pairs of leaves cross each other. Basil is a classic example of a decussate leaf pattern.
    Decussate phyllotaxis of Crassula rupestris
  • In tooth enamel, where bundles of rods cross each other as they travel from the enamel-dentine junction to the outer enamel surface, or near to it.
In this "true bug", Dysdercus decussatus, in the family Pyrrhocoridae, the specific epithet refers to the bandolier-like markings on the back.
  • In taxonomic description where decussate markings or structures occur, names such as decussatus or decussata or otherwise in part containing "decuss..." are common, especially in the specific epithet.[1]

Evolutionary significance

The origin of the

axial twist by which the anterior head, along with the forebrain, is turned by 180° with respect to the rest of the body.[6][7]

See also

References

  1. ISBN 0-398-06179-3
    .
  2. S2CID 16367031
    .
  3. ^ Ramón y Cajal, Santiago (1898). "Estructura del quiasma óptico y teoría general de los entrecruzamientos de las vías nerviosas. (Structure of the Chiasma opticum and general theory of the crossing of nerve tracks)" [Die Structur des Chiasma opticum nebst einer allgemeine Theorie der Kreuzung der Nervenbahnen (German, 1899, Verlag Joh. A. Barth)]. Rev. Trim. Micrográfica (in Spanish). 3: 15–65.
  4. S2CID 30442863
    .
  5. PMID 25528610. Archived from the original
    (PDF) on 2021-07-14. Retrieved 2020-01-01.
  6. S2CID 7399128
    .
  7. PMID 24040928
    .

Further reading

External links

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