| Cervical vertebrae | |
|---|---|
 | |
 A human cervical vertebra | |
| Details | |
| Identifiers | |
| Latin | vertebrae cervicales |
| MeSH | D002574 |
| TA98 | A02.2.02.001 |
| TA2 | 1032 |
| FMA | 9915 |
| Anatomical terms of bone | |
Intetrapods,cervical vertebrae (sg.:vertebra) are thevertebrae of theneck, immediately below theskull. Truncal vertebrae (divided intothoracic andlumbar vertebrae inmammals) lie caudal (toward the tail) of cervical vertebrae.[1] Insauropsid species, the cervical vertebrae bearcervical ribs. Inlizards andsaurischian dinosaurs, the cervical ribs are large; inbirds, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of otheramniotes.[citation needed] Most mammals have seven cervical vertebrae, with the only three known exceptions being themanatee with six, thetwo-toed sloth with five or six, and thethree-toed sloth with nine.[2][3]
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 atransverse foramen, anopening in each transverse process, through which thevertebral artery,vertebral veins, andinferior cervical ganglion pass. The remainder of this article focuses onhuman anatomy.
By convention, the cervicalvertebrae 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 anterior tubercle of the sixth cervical vertebra is known as thecarotid tubercle orChassaignac tubercle (forÉdouard Chassaignac). This separates thecarotid artery from thevertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms ofsupraventricular tachycardia. The carotid tubercle is also used as a landmark foranaesthesia of thebrachial plexus andcervical plexus.
The cervical spinal nerves emerge from above the cervical vertebrae. For example, the cervical spinal nerve 3 (C3) passes above C3.
Theatlas (C1) andaxis (C2) are the two topmost vertebrae.
The atlas (C1) is the topmost vertebra, and along with the axis forms the joint connecting theskull andspine. 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 thisbone is the strongodontoid 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.
Thevertebra 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 acervical rib, which develops from the anterior root of the transverse process. These ribs are usually small, but may occasionally compress blood vessels (such as thesubclavian artery orsubclavian vein) or nerves in thebrachial plexus, causing pain, numbness, tingling, and weakness in the upper limb, a condition known asthoracic 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 theligamentum nuchae attaches to. This process is not always the most prominent of the spinous processes, being found only about 70% of the time, C6 orT1 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.
The movement of nodding the head takes place predominantly throughflexion andextension at theatlanto-occipital joint between the atlas and theoccipital 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, theatlanto-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.
Cervical degenerative changes arise from conditions such asspondylosis,stenosis ofintervertebral discs, and the formation ofosteophytes. The changes are seen onradiographs, 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 spacestenosis or narrowing (3) to the stage of many large osteophytes, severe narrowing of the disc space, and more severevertebral end platesclerosis (4).[5][6][7]
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.[8]
If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, anddiaphragm, which leads torespiratory failure.
Common patterns of injury include the odontoid fracture and thehangman's fracture, both of which are often treated with immobilization in acervical collar orhalo 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. Inclearing the cervical spine, Canadian studies have developed the Canadian C-Spine Rule (CCR) for physicians to decide who should receive radiological imaging.[9]
Thevertebral column is often used as a marker ofhuman anatomy. This includes:
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This article incorporates text in thepublic domain frompage 97 of the 20th edition ofGray's Anatomy(1918)
