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Cervical vertebrae
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{{short description|Vertebrae of the neck}} {{Infobox bone | Name = Cervical vertebrae | Latin = vertebrae cervicales | Image = Cervical vertebrae lateral2.png | Caption = Position of human cervical vertebrae (shown in red). It consists of 7 bones, from top to bottom, [[Atlas (anatomy)|C1]], [[Axis (anatomy)|C2]], C3, C4, C5, C6, and C7. | Image2 = Cervical_vertebra_english.png | Caption2 = A human cervical vertebra }} In [[tetrapod]]s, '''cervical vertebrae''' ({{singular}}: '''vertebra''') are the [[vertebra]]e of the [[neck]], immediately below the [[skull]]. Truncal vertebrae (divided into [[thoracic vertebrae|thoracic]] and [[lumbar vertebrae]] in [[mammal]]s) lie caudal (toward the tail) of cervical vertebrae.<ref>{{cite journal |last1=Schilling |first1=N |title=Evolution of the axial system in craniates: morphology and function of the perivertebral musculature. |journal=Frontiers in Zoology |date=10 February 2011 |volume=8 |issue=4 |pages=3–4 |doi=10.1186/1742-9994-8-4 |pmid=21306656 |pmc=3041741 |doi-access=free }}</ref> In [[sauropsida|sauropsid]] species, the cervical vertebrae bear [[cervical rib]]s. In [[lizard]]s and [[saurischia]]n dinosaurs, the cervical ribs are large; in [[bird]]s, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of other [[amniote]]s.{{citation needed|date=September 2017}} Most mammals have seven cervical vertebrae, with the only three known exceptions being the [[manatee]] with six, the [[two-toed sloth]] with five or six, and the [[three-toed sloth]] with nine.<ref>{{cite journal |doi=10.1186/2041-9139-2-11 |pmid=21548920 |pmc=3120709 |title=Breaking evolutionary and pleiotropic constraints in mammals: On sloths, manatees and homeotic mutations |journal= EvoDevo|volume=2 |pages=11 |year=2011 |last1=Varela-Lasheras |first1=Irma |last2=Bakker |first2=Alexander J |last3=Van Der Mije |first3=Steven D |last4=Metz |first4=Johan AJ |last5=Van Alphen |first5=Joris |last6=Galis |first6=Frietson |doi-access=free }} *{{cite press release |date=May 6, 2011 |title=Sticking their necks out for evolution: Why sloths and manatees have unusually long (or short) necks |website=ScienceDaily |url=https://www.sciencedaily.com/releases/2011/05/110505212314.htm}}</ref><ref>{{cite journal |title=Why do almost all mammals have seven cervical vertebrae? Developmental constraints, ''Hox'' genes, and cancer |journal=J. Exp. Zool.|volume=285 |pages=19–26 |year=1999|last=Galis|first=Frietson|issue=1|doi=10.1002/(SICI)1097-010X(19990415)285:1<19::AID-JEZ3>3.0.CO;2-Z|pmid=10327647|bibcode=1999JEZ...285...19G }}</ref> In humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a [[transverse foramen]], an [[foramen|opening]] in each transverse process, through which the [[vertebral artery]], [[vertebral veins]], and [[inferior cervical ganglion]] pass. The remainder of this article focuses on [[human anatomy]]. ==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. ==Function== The movement of nodding the head takes place predominantly through [[Anatomical terms of motion|flexion]] and [[Anatomical terms of motion|extension]] at the [[atlanto-occipital joint]] between the atlas and the [[occipital bone]]. However, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself. This movement between the atlas and occipital bone is often referred to as the "yes joint", owing to its nature of being able to move the head in an up-and-down fashion. The movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the [[atlanto-axial joint]]. A small amount of rotation of the vertebral column itself contributes to the movement. This movement between the atlas and axis is often referred to as the "no joint", owing to its nature of being able to rotate the head in a side-to-side fashion. ==Clinical significance== {{anchor|lines}}{{multiple image | direction = horizontal | footer = ''Cervical lines'' are annotations used in [[medical imaging]] of the cervical vertebrae, here seen on [[projectional radiography|X-ray]] and [[CT scan|CT]], respectively. Incongruencies indicate [[cervical fracture]], [[spondylolisthesis]] and/or ligament injury. | image1 = X-ray of vertebral lines.jpg | width1 = 212 | image2 = Vertebral lines.png | width2 = 190 }} '''Cervical degenerative changes''' arise from conditions such as [[spondylosis]], [[stenosis]] of [[intervertebral disc]]s, and the formation of [[osteophyte]]s. The changes are seen on [[radiograph]]s, which are used in a grading system from 0–4 ranging from no changes (0) to early with minimal development of osteophytes (1) to mild with definite osteophytes (2) to moderate with additional disc space [[stenosis]] or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severe [[vertebra |vertebral end plate]] [[Sclerosis (medicine)|sclerosis]] (4).<ref>{{cite journal|last1=Ofiram|first1=Elisha|last2=Garvey|first2=Timothy A|last3=Schwender|first3=James D|last4=Denis|first4=Francis|last5=Perra|first5=Joseph H|last6=Transfeldt|first6=Ensor E|last7=Winter|first7=Robert B|last8=Wroblewski|first8=Jill M|title=Cervical degenerative index: a new quantitative radiographic scoring system for cervical spondylosis with interobserver and intraobserver reliability testing|journal=Journal of Orthopaedics and Traumatology|date=2009|volume=10|issue=1|pages=21–26|doi=10.1007/s10195-008-0041-3|pmc=2657349|pmid=19384631}}</ref><ref>{{cite web|last1=Garfin|first1=Steven R|last2=Bono|first2=Christopher M|title=Degenerative Cervical Spine Disorders|url=http://www.spineuniverse.com/conditions/neck-pain/degenerative-cervical-spine-disorders|website=spineuniverse|access-date=25 October 2016|url-status=live|archive-url=https://web.archive.org/web/20161028015727/http://www.spineuniverse.com/conditions/neck-pain/degenerative-cervical-spine-disorders|archive-date=28 October 2016}}</ref><ref>{{cite journal|last1=Christie|first1=A|last2=Läubli|first2=R|last3=Guzman|first3=R|last4=Berlemann|first4=U|last5=Moore|first5=R J|last6=Schroth|first6=G|last7=Vock|first7=P|last8=Lövblad|first8=K O|title=Degeneration of the cervical disc: histology compared with radiography and magnetic resonance imaging|journal=Neuroradiology|date=2005|volume=47|issue=10|pages=721–729|doi=10.1007/s00234-005-1412-6|pmid=16136264|s2cid=10970503|url=http://doc.rero.ch/record/310763/files/234_2005_Article_1412.pdf}}</ref> Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. C4 and C5 are the areas that see the highest amount of cervical spine trauma.<ref>[https://www.nscisc.uab.edu/PublicDocuments/reports/pdf/2012%20NSCISC%20Annual%20Statistical%20Report%20Complete%20Public%20Version.pdf 2012 Annual Report] {{webarchive|url=https://web.archive.org/web/20140222023936/https://www.nscisc.uab.edu/PublicDocuments/reports/pdf/2012%20NSCISC%20Annual%20Statistical%20Report%20Complete%20Public%20Version.pdf |date=2014-02-22 }}, Table 64, page 66</ref> If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and [[Thoracic diaphragm|diaphragm]], which leads to [[respiratory failure]]. Common patterns of injury include the odontoid fracture and the [[hangman's fracture]], both of which are often treated with immobilization in a [[cervical collar]] or [[Orthotics|halo brace]]. A common practice is to immobilize a patient's cervical spine to prevent further damage during transport to hospital. This practice has come under review recently as incidence rates of unstable spinal trauma can be as low as 2% in immobilized patients. In [[clearing the cervical spine]], Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.<ref>{{cite web|url=http://www.ohri.ca/emerg/cdr/cspine.html|title=Canadian C-Spine Rule - Emergency Medicine Research - Ottawa Hospital Research Institute|website=www.ohri.ca|access-date=6 May 2018|url-status=live|archive-url=https://web.archive.org/web/20170514050959/http://www.ohri.ca/emerg/cdr/cspine.html|archive-date=14 May 2017}}</ref> ===Landmarks=== {{See also|Anatomical landmark}} The [[vertebral column]] is often used as a marker of [[Human body|human anatomy]]. This includes: * At C1, base of the [[nose]] and the [[hard palate]] * At C2, the [[Tooth|teeth]] of a closed mouth * At C3, the [[mandible]] and [[hyoid bone]] * At C4, the [[common carotid artery]] bifurcates. * From C4–5, the [[thyroid cartilage]]<ref name="mm">{{MedicalMnemonics|3548|}}</ref> * From C6–7, the [[cricoid cartilage]]<ref name="mm" /> * At C6, the [[Esophagus|oesophagus]] becomes continuous with the [[laryngopharynx]] and also where the [[larynx]] becomes continuous with the [[trachea]]. It is also the level where the [[carotid]] pulse can be palpated against the transverse process of the C6 vertebrae. ==Additional images== <gallery> File:Computed tomographs of normal cervical vertebrae (thumbnail).jpg|[[Commons:Scrollable computed tomography images of normal cervical vertebrae|Scrollable computed tomography images of normal cervical vertebrae]] File:Cervical vertebrae animation small.gif|Position of cervical vertebrae (shown in red). Animation. File:Blausen 0222 CervicalSpine.png|Illustration of cervical vertebrae File:Cervical vertebrae - close-up - animation2.gif|Shape of cervical vertebrae (shown in blue and yellow). Animation. File:Human cervical vertebra.stl|3D image File:Cervical vertebrae lateral3.png|Cervical vertebrae, lateral view (shown in blue and yellow) File:Illu vertebral column.svg|Vertebral column File:Gray 111 - Vertebral column-coloured.png|Vertebral column File:HWS seitlich Annotation.jpg|X-ray of cervical vertebrae File:Cervical XRayFlexionExtension.jpg|X-ray of cervical spine in flexion and extension File:Gray86.png|First cervical vertebra, or atlas File:Gray87.png|Second cervical vertebra, or epistropheus, from above File:Gray88.png|Second cervical vertebra, epistropheus, or axis, from the side File:Gray89.png|Seventh cervical vertebra File:Gray305.png|Posterior atlanto-occipital membrane and atlantoaxial ligament File:Gray308.png|Median sagittal section through the occipital bone and first three cervical vertebrae File:Gray384.png|Section of the neck at about the level of the sixth cervical vertebra File:Cervical Spine Anterior View.png|Anterior view of cervical spine showing the vertebral arteries along with the spinal nerves. See this in 3d [https://sketchfab.com/models/98f4cbd06fdf4350a4c3485439705607 here.] </gallery> ==See also== {{Portal |Anatomy}} {{Anatomy-terms}} * [[Vertebral column]] * [[Cervical fracture]] ==References== {{Gray's}} {{Reflist|32em}} ==External links== {{Commons category|Cervical vertebrae}} * [http://biology.kenyon.edu/heithausp/cat-tutorial/vertebrae/cervical.htm Diagram] at kenyon.edu * [http://www.spineuniverse.com/displayarticle.php/article1021.html Cervical Spine Anatomy] * [https://web.archive.org/web/20170925181030/http://www.lifehugger.com/moc/132/cervical-vertebrae-landmarks-each-level Mnemonic for Landmarks] * [https://web.archive.org/web/20120502173503/http://anatomyhq.org/quizzes/labelling-exercises/cervical-vertebra/ Cervical vertebra quiz] * [https://sites.google.com/a/umich.edu/bluelink/curricula/first-year-medical-curriculum/sequence-1-Foundations/session-2-spinal-cord-and-peripheral-nervous-system/bluelink Cervical vertebrae]{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }} - BlueLink Anatomy - University of Michigan Medical School {{Bones of torso}} {{spinal nerves}} {{Authority control}} {{DEFAULTSORT:Cervical Vertebrae}} [[Category:Bones of the head and neck]] [[Category:Bones of the thorax]] [[Category:Bones of the vertebral column]]
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