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

/ra·chis/ (ra´kis) vertebral column.

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.

rachis

1. the vertebral column.
2. the shaft of a feather.
References in periodicals archive ?
Plants terrestrial; rhizomes short, stout, ascending, scaly, the scales denticulate; leaves up to 2 m long; petioles about as long as the laminae; laminae 3- to 5-pinnate-pinnatifid, deltate or pentagonal to broadly lanceolate, gradually tapered to a pinnatifid apex, buds on rachises absent; basal pinnae inequilateral prolonged on the basiscopic side; suprabasal pinnae equilateral or nearly so; pinnules of suprabasal pinnae anadromic; rachises, costae, and costules with a thickened marginal ridge surcurrent on the segments of the next higher order (i.
Megalastrum platylobum is distinctive by hairs of mixed lengths along the pinna rachises abaxially.
This specimen, from Cerro Trumuquire in the state of Sucre, resembles Megalastrum biseriale by small lamina size and by lamina cutting; however, it differs by basal pinnae equilateral, smaller scales on the lamina rachises (2.
Pinna rachis scales clathrate; pinna rachises and costules abaxially evenly and densely pubescent by reddish hairs 0.
8 m long), laminae medially 1-pinnate-pinnatisect, and pinnae rachises abaxially with long (0.
1/3 the way to the rachises, about as long as the sterile portion, the segments deltate, obtuse; rachis on both sides with dark sclerenchyma exposed, pubescent, the hairs spreading, reddish, rigid and straight, 1-furcate,ca.
Diplazium celtidifolium Kunze has similar linear and lanceolate scales on the rachises, and also has buds on the axils of distal pinnae, but differs from D.
Leaves monomorphic, 16-32 x 6-12 cm; stipes 50-60% the length of the fronds, atropurpureous to ebeneous, mainly glabrous, with scattered scales near the base, shining to weakly glaucous; stipe scales narrowly triangular, stramineous proximally, castaneous distally, margins with spreading to recurved teeth; blades oblong to broadly obovate, pinnate (entire when young), glabrous, pinna bases overlapping the rachis; rachises atropurpureous to ebeneus, abaxially glabrous, adaxially with minute scattered hairs 0.
50 cm tall; dark brown to blackish petioles and rachises, the rachises not flexuous, bearing hairs and filiform scales, adaxially slightly sulcate and with two narrow wings; the laminae light green, 2-3-pinnate at the base, sometimes the proximal pinnules only lobate, subcoriaceous and glabrous on the laminar tissue; pinnules varying from ovate to lanceolate (Figs.
1E; 2A); leaves 30-75 x 8-20 cm, closely spaced or to 3 cm apart; petioles 10-20 cm x 1-2 mm, castaneous, lustrous, very slightly glaucous or not, glabrous or with a few scales at the base like those of the rhizomes; rachises flexuous, glabrous (Fig.
The hairs cover the stipes, rachises, indusia, and laminar tissue on both surfaces.
Blades 4-15(21) cm long x 1-5(13) cm wide, membranaceous, 1-pinnate proximally, with long attenuate pinnatifid apices; rachises greenish to stramineous, dull, with narrow green wings up to 0.