rachis

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Related to rachises: rachial

spine

 [spīn]
1. a thornlike process or projection; called also acantha and spina.
2. the rigid bony structure in the midline of the back, composed of the vertebrae; called also backbone, spinal column, and vertebral column.



The spinal column is the axis of the skeleton; the skull and limbs are in a sense appendages. The vertebrae also provide the protective bony corridor (spinal canal) through which the spinal cord passes; they can move to a certain extent and so give flexibility to the spine, allowing it to bend forward, sideways and, to a lesser extent, backward. In the areas of the neck and lower back, the spine also can pivot, which permits the turning of the head and torso.

There are usually 24 movable vertebrae and nine that are fused together. The topmost are the seven cervical vertebrae, which form the back of the neck, supporting the skull. The head turns from side to side by means of a pivotal motion between the two highest vertebrae. Below these are the 12 thoracic vertebrae, the supports on which the ribs are hinged, and then the five lumbar vertebrae, the largest movable vertebrae (the cervical are the smallest). Below the lumbar vertebrae, the spine terminates with two groups of vertebrae fused into single bones: the sacrum, composed of five vertebrae, and the coccyx, composed of four vertebrae. Viewed from the side of the body, the spine has the shape of a gentle double S curve.
Malformations of the Spine. Of the various types of spinal malformations, some are congenital and others the result of postural defects or injuries. spina bifida is congenital. kyphosis may occasionally be congenital but is more often caused by one of the diseases that attack the structure of the bones. The most common of these is pott's disease, or tuberculosis affecting the vertebrae and soft tissues of the spine. Another is osteitis deformans, a type of bone inflammation in which parts of the bone are replaced by softer tissue. scoliosis is a curvature of the spine toward one side.
cervical spine that portion of the spine comprising the cervical vertebrae.
lumbar spine that portion of the spine comprising the lumbar vertebrae.
thoracic spine that part of the spine comprising the thoracic vertebrae.

ver·te·bral col·umn

[TA]
the series of vertebrae that extend from the cranium to the coccyx, providing support and forming a flexible bony case for the spinal cord.

rachis

(rā′kĭs)
n. pl. rachises or rachides (răk′ĭ-dēz′, rā′kĭ-)
1.
a. The main stem of an elongated inflorescence, as in a grass.
b. The main axis of a pinnately compound leaf or of a fern frond.
2. The main shaft of a bird's feather, especially the part to which the barbs are attached.
3. The spinal column.

ra′chi·al adj.

ver·te·bral col·umn

(vĕr'tĕ-brăl kol'ŭm) [TA]
The series of vertebrae that extend from the cranium to the coccyx, providing support and forming a flexible bony case for the spinal cord.
Synonym(s): columna vertebralis [TA] , backbone, rachis, spina, spinal column, spine (2) .

rachis

or

rhacis

any central axis, particularly that of a feather.
References in periodicals archive ?
Blechnum sprucei distinguishes by the presence of long radicant rachises, which allow the plant to reproduce vegetatively, a sporophytic character mostly preferred when the species is treated or included in keys.
The amount of total volatiles emitted by intact racemes was not significantly different (P [is greater than] 0.05) from those of only florets or only rachises (Table 2).
Concentration of the five most abundant volatile classes and total volatiles in intact racemes, florets and rachises of alfalfa.
Class of volatiles Intact racemes Florets([double dagger]) --[micro]g/g fresh weight-- Aldehydes 25.54a([dagger]) 39.29a Alcohols 6.38c 15.05a Ketones 6.99b 15.27a Esters 0.09a 0.99a Terpenes 0.12a 0.26a Total 41.81a 69.21a Inflorescence Class of volatiles rachises --[micro]g/g fresh weight-- Aldehydes 34.62a Alcohols 11.37b Ketones 7.37b Esters 0.45a Terpenes 0.25a Total 56.68a ([dagger]) Means in each row followed by the same letter are not different at P [is less than or equal to] 0.05 according to Duncan's multiple range test.
The similarity in volatile amount and composition of intact inflorescences versus florets and rachises taken separately supports the use of whole inflorescences in studies on volatiles rather than single florets the handling of which might also influence the measurements.
The amount of DM in the vegetative (leaves, stems) and the nongrain reproductive organs (rachises, glumes, lemma, and palea) on a per plant basis, increased to a maximum at 3 wk after anthesis, and thereafter decreased rapidly (Fig.
Dry Matter Losses from Various Leaves, Stem Segments, and Rachises
These losses were significantly more than that lost by rachises (2-5%).
It was positively correlated with the number of primary rachises, and negatively correlated with leaf area per spikelet and biomass per spikelet.