axis (anatomy)

Information about axis (anatomy)

Bone: Axis (anatomy)
Second cervical vertebra, or epistropheus, from above.
Posterior atlantoöccipital membrane and atlantoaxial ligament. (Axis visible at center.)
subject #21 99
In anatomy, the second cervical vertebra (C2) of the spine is named the axis (from Latin axis, "axle") or epistropheus.

It forms the pivot upon which the first cervical vertebra (the atlas), which carries the head, rotates.

The most distinctive characteristic of this bone is the strong odontoid process ("dens") which rises perpendicularly from the upper surface of the body. That peculiar feature gives to the vertebra a rarely-used third name: vertebra dentata.

The body

The body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.

It presents in front a median longitudinal ridge, separating two lateral depressions for the attachment of the Longus colli muscles.

Its under surface is concave from before backward and convex from side to side.

Other features

The dens, or odontoid process, exhibits a slight constriction or neck where it joins the body.

The pedicles are broad and strong, especially in front, where they coalesce with the sides of the body and the root of the odontoid process. They are covered above by the superior articular surfaces.

The laminae are thick and strong, and the vertebral foramen large, but smaller than that of the atlas.

The transverse processes are very small, and each ends in a single tubercle; each is perforated by the transverse foramen, which is directed obliquely upward and laterally.

The superior articular surfaces are round, slightly convex, directed upward and laterally, and are supported on the body, pedicles, and transverse processes.

The inferior articular surfaces have the same direction as those of the other cervical vertebrae.

The superior vertebral notches are very shallow, and lie behind the articular processes; the inferior lie in front of the articular processes, as in the other cervical vertebrae.

The spinous process is large, very strong, deeply channelled on its under surface, and presents a bifid, tuberculated extremity.

Additional images


Median sagittal section through the occipital bone and first three cervical vertebræ.

Sagittal section of nose mouth, pharynx, and larynx.


See also

External links

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.


Spine [ edit]
general structures: body of vertebra, vertebral arch (pedicle, lamina, vertebral notch), foramina (vertebral, intervertebral), processes (transverse, articular, spinous) cervical vertebrae: C1 (anterior arch, posterior arch, lateral mass), C2 (dens), C7, posterior tubercle, foramen transversarium thoracic vertebrae: costal facets (superior, inferior, transverse) lumbar vertebrae: accessory process, mammillary process sacrum/coccyx: pelvic surface (anterior sacral foramina, dorsal surface (posterior sacral foramina, median sacral crest, medial sacral crest, lateral sacral crest), lateral surface, base, sacral hiatus
Anatomy (from the Greek ἀνατομία anatomia, from ἀνατέμνειν
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In vertebrates, cervical vertebrae (singular: vertebra) are those vertebrae immediately behind (caudal to) the skull.

Variation among species

In some species, some parts of the skull may be composed of vertebra-like elements, e.g.
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vertebral column (backbone or spine) is a column of 34 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs. It houses the spinal cord in its spinal canal.
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The Vertebral Column (singular: vertebra) are the individual irregular bones that make up the spinal column (aka ischis) — a flexuous and flexible column.
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In anatomy, the atlas (C1) is the topmost (first) cervical vertebra of the spine.

It is named for the Atlas of mythology, because it supports the globe of the head.
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head of an animal is the rostral part (from anatomical position) that usually comprises the brain, eyes, ears, nose, and mouth (all of which aid in various sensory functions, such as sight, hearing, smell, and taste).
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Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals.
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The dens or odontoid process or odontoid peg of the axis exhibits a slight constriction or neck, where it joins the body.

On its anterior surface is an oval or nearly circular facet for articulation with that on the anterior arch of the atlas.
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The Longus colli muscle is a muscle of the human body.

The Longus colli is situated on the anterior surface of the vertebral column, between the atlas and the third thoracic vertebra.
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MUSCLE (multiple sequence comparison by log-expectation) is public domain, multiple sequence alignment software for protein and nucleotide sequences.
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DEN may refer to:
  • The country Denmark
  • The IATA code for Denver International Airport
  • Digital Entertainment Network


Den may refer to:
  • Den (architecture), a part of a house similar to the family room

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The dens or odontoid process or odontoid peg of the axis exhibits a slight constriction or neck, where it joins the body.

On its anterior surface is an oval or nearly circular facet for articulation with that on the anterior arch of the atlas.
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Pedicle or pedicel may refer to:
  • Pedicle (anatomy), the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures

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Lamina may refer to:
  • Lamina of the vertebral arch
  • Planar lamina, a two-dimensional planar closed surface with mass and density, in mathematics
  • A thin plate, sheet or layer, such as:

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In a typical vertebra, the vertebral foramen is the foramen formed by the anterior segment (the body), and the posterior part, the vertebral arch.

The vertebral foramen begins at cervical vertebrae #1 (atlas) and continues inferior to lumbar vertebrae #5.
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The transverse processes of a vertebra, two in number, project one at either side from the point where the lamina joins the pedicle, between the superior and inferior articular processes. They serve for the attachment of muscles and ligaments.
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The transverse processes of cervical vertebrae are each pierced by the transverse foramen, which, in the upper six vertebrae, gives passage to the vertebral artery and vein and a plexus of sympathetic nerves.
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Released October 31, 2007
Genre J-Pop
Length N/A
Label Geneon
Producer(s) I've Sound

Mami Kawada singles chronology

Get my way!
(2007) JOINT
(2007)

JOINT
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Released October 31, 2007
Genre J-Pop
Length N/A
Label Geneon
Producer(s) I've Sound

Mami Kawada singles chronology

Get my way!
(2007) JOINT
(2007)

JOINT
..... Click the link for more information.
In vertebrates, cervical vertebrae (singular: vertebra) are those vertebrae immediately behind (caudal to) the skull.

Variation among species

In some species, some parts of the skull may be composed of vertebra-like elements, e.g.
..... Click the link for more information.
Spine [ edit]
general structures: body of vertebra, vertebral arch (pedicle, lamina, vertebral notch), foramina (vertebral, intervertebral), processes (transverse, articular, spinous) cervical vertebrae:
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The articular processes (zygapophyses) of a vertebra, two superior and two inferior, spring from the junctions of the pedicles and laminæ.
  • The superior processes project upward from a lower vertebra, and their articular surfaces are directed more or less backward.

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The spinous process of a vertebra is directed backward and downward from the junction of the laminae (in humans), and serves for the attachment of muscles and ligaments. In animals without an erect stance, the process points upward and may slant forward or backward.
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Bifurcated rib
Classification & external resources

ICD-10 Q 76.7
ICD-9 756.3

A bifid rib or bifurcated rib or sternum bifidum is a congenital abnormality occurring in about 1.2% of the population. Bifid ribs occur in up to 8.
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The axis is ossified from five primary and two secondary centers.

The body and vertebral arch are ossified in the same manner as the corresponding parts in the other vertebrae, viz., one center for the body, and two for the vertebral arch.
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University of Michigan, Ann Arbor (U of M, UM or simply Michigan) is a coeducational public research university in the state of Michigan. The university was founded in 1817 in Detroit, about 20 years before the territory of Michigan officially became a state,
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University of Michigan, Ann Arbor (U of M, UM or simply Michigan) is a coeducational public research university in the state of Michigan. The university was founded in 1817 in Detroit, about 20 years before the territory of Michigan officially became a state,
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Public domain comprises the body of knowledge and innovation (especially creative works such as writing, art, music, and inventions) in relation to which no person or other legal entity can establish or maintain proprietary interests within a particular legal jurisdiction.
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Henry Gray's Anatomy of the Human Body (or Gray's Anatomy as it has commonly been shortened) is an English-language human anatomy textbook widely regarded as a classic work on the subject.
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vertebral column (backbone or spine) is a column of 34 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs. It houses the spinal cord in its spinal canal.
..... Click the link for more information.

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