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. In some judicial hangings the odontoid process may break and hit the medulla oblongata, causing death.
The body [ edit ]
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 [ edit ]
dens, or odontoid process, exhibits a slight constriction or neck where it joins the body.
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.
laminae are thick and strong, and the vertebral foramen large, but smaller than that of the atlas.
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.
articular surfaces are round, slightly convex, directed upward and laterally, and are supported on the body, pedicles, and transverse processes.
articular surfaces have the same direction as those of the other cervical vertebrae.
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.
spinous process is large, very strong, deeply channelled on its under surface, and presents a bifid, tuberculated extremity.
Additional images [ edit ]
Its shape and position (shown in red) from above. The skull is shown in semi-transparent.
Posterior atlantooccipital membrane and atlantoaxial ligament. (Axis visible at center.)
Median sagittal section through the occipital bone and first three cervical vertebræ.
Sagittal section of nose mouth, pharynx, and larynx.
See also [ edit ]
External links [ edit ]
This article incorporates text from a public domain edition of Gray's Anatomy .
T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12
costal facets ( superior, inferior, transverse)
Uncinate process of vertebra
specific ribs ( 1, 2, 9, 10, 11, 12, true – 1–7, false – 8–12, floating – 11–12)
parts ( Angle, Tubercle, Costal groove, Neck, Head)