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Cervical vertebrae
In vertebrates, cervical vertebrae (singular: vertebra) are those vertebrae immediately behind (caudal to) the skull. Additional recommended knowledge
Variation among speciesIn some species, some parts of the skull may be composed of vertebra-like elements, e.g. the occipital bone in humans is composed of four vertebra-like segments. In many vertebrate species, cervical vertebrae are variable in number; however, almost all mammals have seven (including those with very short necks, such as elephants or whales, and those with very long necks, such as giraffes). The few exceptions include the manatee and the two-toed sloth, which each have only six cervical vertebrae, and the three-toed sloth with nine cervical vertebrae. Thoracic vertebrae in all species are defined as those vertebrae which also carry a pair of ribs, and lie caudal to the cervical vertebrae. 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 foramen (hole) in each transverse process, through which passes the vertebral artery. The remainder of this article focuses upon human anatomy. General characteristics (C3-C6)These are the general characteristics of the third through sixth cervical vertebrae. (The first, second, and seventh vertebrae are extraordinary, and detailed later.)
Special cervical vertebrae (C1, C2, and C7)
Movements of the cervical spineThe movements of flexion and extension of the head take place predominantly at the joint between the first cervical vertebra and the occipital bone, the atlanto-occipital joint. However, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself. The movement of rotating the head to left and right happens almost entirely at the joint between the first and second cervical vertebrae, the atlanto-axial joint. A small amount of rotation of the vertebral column itself contributes to the movement. LandmarksThe thyroid cartilage is from C4 to C5.[1] The cricoid cartilage is from C6 to C7.[1] Clinical significanceInjuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. If it does occur, however, it may cause death or profound disability, including paralysis of the arms, legs, and 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 Halo brace. Additional imagesReferencesCategories: Head and neck | Skeletal system |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cervical_vertebrae". A list of authors is available in Wikipedia. |