decussate on:
[Wikipedia]
[Google]
[Amazon]
Decussation is used in biological contexts to describe a crossing (due to the shape of the Roman numeral for ten, an uppercase 'X' (), ). In Latin 
* 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
Why does the nervous system decussate?
Stanford Neuroblog
Decussation is used in biological contexts to describe a crossing (due to the shape of the Roman numeral for ten, an uppercase 'X' (), ). In Latin anatomical
Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...
terms, the form is used, e.g. .
Similarly, the anatomical term chiasma is named after the Greek uppercase 'Χ' (chi
Chi or CHI may refer to:
Greek
*Chi (letter), the Greek letter (uppercase Χ, lowercase χ);
Chinese
* ''Chi'' (length) (尺), a traditional unit of length, about ⅓ meter
* Chi (mythology) (螭), a dragon
*Chi (surname) (池, pinyin: ''chí' ...
). Whereas a decussation refers to a crossing within the central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
, various kinds of crossings in the peripheral nervous system are called chiasma.
Examples include:
* In the brain, where nerve fibers obliquely cross from one lateral side of the brain to the other, that is to say they cross at a level other than their origin. See for examples Decussation of pyramids and sensory decussation
In neuroanatomy, the sensory decussation or decussation of the lemnisci is a decussation (i.e. crossover) of axons from the gracile nucleus and cuneate nucleus, which are responsible for fine touch, vibration, proprioception and two-point discri ...
. In neuroanatomy
Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...
, the term ''chiasma'' is reserved for crossing of- or within nerves such as in the optic chiasm
In neuroanatomy, the optic chiasm, or optic chiasma (; , ), is the part of the brain where the optic nerves cross. It is located at the bottom of the brain immediately inferior to the hypothalamus. The optic chiasm is found in all vertebra ...
.
* In botanical
Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...
leaf taxology, the word ''decussate'' describes an 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
Basil (, ; ''Ocimum basilicum'' , also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a tender plant, and is used in cuisines worldwide. In Western cuisine, the generic term "basil" refers to the variety also kn ...
is a classic example of a decussate leaf pattern.
* 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 taxonomic
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. A ...
description where decussate markings or structures occur, names such as or or otherwise in part containing "decuss..." are common, especially in the specific epithet.
Evolutionary significance
The origin of the contralateral organization, the optic chiasm and the major decussations on the nervous system ofvertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
has been a long standing puzzle to scientists. The visual map theory of Ramón y Cajal Ramón or Ramon may refer to:
People Given name
* Ramon (footballer, born 1998), Brazilian footballer
* Ramón (footballer, born 1990), Brazilian footballer
*Ramón (singer), Spanish singer who represented Spain in the 2004 Eurovision Song Contest ...
has long been popular but has been criticized for its logical inconsistence. More recently, it has been proposed that the decussations are caused by an axial twist by which the anterior head, along with the forebrain
In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three primary b ...
, is turned by 180° with respect to the rest of the body.
See also
* Definition of types of crossings * Palpebral commissure (of the eye) *Commissure
A commissure () is the location at which two objects abut or are joined. The term is used especially in the fields of anatomy and biology.
* The most common usage of the term refers to the brain's commissures, of which there are five. Such a commi ...
* Chiasm
* Contralateral brain
The contralateral organization of the forebrain (Latin: contra‚ against; latus‚ side; lateral‚ sided) is the property that the hemispheres of the cerebrum and the thalamus represent mainly the contralateral side of the body. Consequently, th ...
* Fissure (anatomy)
In biological morphology and anatomy, a sulcus (pl. ''sulci'') is a furrow or fissure (Latin ''fissura'', plural ''fissurae''). It may be a groove, natural division, deep furrow, elongated cleft, or tear in the surface of a limb or an organ, ...
References
Further reading
Why does the nervous system decussate?
Stanford Neuroblog
External links
* {{Authority control Biology terminology Anatomical terminology