Editing Cervical vertebrae (section)

==Structure==
[[File:Gray85.png|thumb|300px|Side view of a typical cervical vertebra]]
[[File:Okapi Giraffe Neck.png|thumb|Despite greatly differing neck lengths, [[okapi]] (left) and giraffe (right) both have seven cervical vertebrae. The giraffe's neck is elongated by [[heterochrony]], extension of the time for the [[embryonic development]] of these bones.<ref>{{cite book |last=Hillis |first=David M. |title=Principles of Life |url=https://books.google.com/books?id=-WQdBQAAQBAJ&pg=PA280 |date=May 2011 |publisher=Palgrave Macmillan |isbn=978-1-4641-6298-5 |pages=280– |url-status=live |archive-url=https://web.archive.org/web/20180506014656/https://books.google.com/books?id=-WQdBQAAQBAJ&pg=PA280 |archive-date=2018-05-06 }}</ref>]]

By convention, the cervical [[vertebra]]e are numbered, with the first one (C1) closest to the skull and higher numbered vertebrae (C2–C7) proceeding away from the skull and down the spine.
The general characteristics of the third through sixth cervical vertebrae are described here. The first, second, and seventh vertebrae are extraordinary, and are detailed later.
* The bodies of these four vertebrae are small, and broader from side to side than from front to back.
** The ''anterior'' and ''posterior surfaces'' are flattened and of equal depth; the former is placed on a lower level than the latter, and its inferior border is prolonged downward, so as to overlap the upper and forepart of the vertebra below.
** The ''upper surface'' is concave transversely, and presents a projecting lip on either side.
** The ''lower surface'' is concave from front to back, convex from side to side, and presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra.
* The [[Vertebra|pedicles]] are directed laterally and backward, and attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower.
* The [[Vertebra|laminae]] are narrow and thinner above than below; the [[vertebral foramen]] is large and of a triangular form.
* The [[Vertebra|spinous process]] is short and bifid, the two divisions being often of unequal size. Because the spinous processes are so short, certain superficial muscles (the [[trapezius]] and [[Splenius capitis muscle|splenius capitis]]) attach to the [[nuchal ligament]] rather than directly to the vertebrae; the nuchal ligament itself attaching to the spinous processes of C2–C7 and to the posterior tubercle of the atlas.
* The superior and inferior [[articular processes]] of cervical vertebrae have fused on either or both sides to form '''articular pillars''', columns of bone that project laterally from the junction of the pedicle and lamina.
* The [[Joint|articular facets]] are flat and of an oval form:
** the ''superior'' face backward, upward, and slightly medially.
** the ''inferior'' face forward, downward, and slightly laterally.
* The [[Vertebra|transverse processes]] are each pierced by the '''transverse foramen''' also known as the '''foramen transversarium''', which, in the upper six vertebrae, gives passage to the [[vertebral artery]] and [[vertebral vein|vein]], as well as a plexus of [[Sympathetic nervous system|sympathetic nerves]]. Each process consists of an anterior and a posterior part. These two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding [[spinal nerve]].
** The anterior portion is the homologue of the [[rib]] in the [[thorax|thoracic]] region, and is therefore named the ''costal process'' or ''costal element''. It arises from the side of the body, is directed laterally in front of the foramen, and ends in a tubercle, the [[Vertebra|anterior tubercle]].
** The posterior part, the true transverse process, springs from the vertebral arch behind the foramen and is directed forward and laterally; it ends in a flattened vertical tubercle, the [[Vertebra|posterior tubercle]].

{{anchor|Chassignac}}The anterior tubercle of the sixth cervical vertebra is known as the '''carotid tubercle''' or '''Chassaignac tubercle''' (for [[Édouard Chassaignac]]). This separates the [[carotid artery]] from the [[vertebral artery]] and the carotid artery can be massaged against this tubercle to relieve the symptoms of [[supraventricular tachycardia]]. The carotid tubercle is also used as a landmark for [[anaesthesia]] of the [[brachial plexus]] and [[cervical plexus]].

The cervical spinal nerves emerge from above the cervical vertebrae. For example, the cervical spinal nerve 3 (C3) passes above C3.

===Atlas and axis===
{{Main|Atlas (anatomy)|Axis (anatomy)}}

The [[Atlas (anatomy)|atlas]] (C1) and [[Axis (anatomy)|axis]] (C2) are the two topmost vertebrae.

The atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting the [[Human skull|skull]] and [[vertebral column|spine]]. It lacks a vertebral body, spinous process, and discs either superior or inferior to it. It is ring-like and consists of an anterior arch, posterior arch, and two lateral masses.

The axis (C2) forms the pivot on which the atlas rotates. The most distinctive characteristic of this [[bone]] is the strong [[odontoid process]] (dens) that rises perpendicularly from the upper surface of the body and articulates with C1. 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.

===Vertebra prominens===
[[File:C7 animation small.gif|thumb|right|200px|Position of C7 shown in red.]]
The '''vertebra prominens''', or C7, has a distinctive long and prominent spinous process, which is palpable from the skin surface. Sometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a [[cervical rib]], which develops from the anterior root of the transverse process. These ribs are usually small, but may occasionally compress blood vessels (such as the [[subclavian artery]] or [[subclavian vein]]) or nerves in the [[brachial plexus]], causing pain, numbness, tingling, and weakness in the upper limb, a condition known as [[thoracic outlet syndrome]]. Very rarely, this rib occurs in a pair.

The long spinous process of C7 is thick and nearly horizontal in direction. It is not bifurcated, and ends in a tubercle that the [[ligamentum nuchae]] attaches to. This process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 or [[Thoracic vertebrae|T1]] can sometimes be the most prominent.

The transverse processes are of considerable size; their posterior roots are large and prominent, while the anterior are small and faintly marked. The upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation.

The transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.

On the left side, it occasionally gives passage to the vertebral artery; more frequently, the vertebral vein traverses it on both sides, but the usual arrangement is for both artery and vein to pass in front of the transverse process, not through the foramen.