![]() While approximately half of the rotation of the neck occurs at the C1-C2 articulation, it is limited by the alar ligaments spanning from the odontoid to the anterior rim of the foramen magnum. This ligament keeps C1 from sliding forward on C2 during flexion. Most notable is the transverse atlantal ligament which spans between the atlantal condyles trapping the odontoid anteriorly against the anterior arch of C1. Crucial stabilizing ligaments maintain the relationships between the occipito-atlanto-axial articulations.C2, known as the axis, provides a bearing surface on which the atlas may rotate, but its most distinctive characteristic is the vertically projecting odontoid process that serves as a pivotal restraint against horizontal displacements of the atlas.Half of the flexion and extension of the neck occur at this articulation. C1, the atlas, is a ring of bone that supports the base of the skull at the atlanto-occipital articulation.In the cervical spine C1 and C2 have a distinct morphology compared to C3-C7.The endplates are important in the diffusion of nutrition and waste between the blood supply of the vertebral bodies and the avascular discs. Between them lie the intervertebral disc composed of a circumferential annulus fibrosis and a central nucleus pulposus. An endplate composed of hyaline cartilage lies on both the superior and inferior endplates of the vertebral bodies.It sees the dorso-ventral translational forces which has been implicated in pars fractures. The pars interarticularis is the portion of the lamina that lies between the superior and inferior articular processes.The articular processes form the facet or zygapophyseal joints. The transverse processes extend from the sides of the vertebral arches. Near the junction of the pedicles and the laminae are found the lateral transverse processes and the superior and inferior articular processes.The pedicles, laminae, and dorsum of the body thus form the vertebral foramen, a complete osseous ring that encloses the spinal cord.These are united dorsally by a pair of arched flat laminae that are surmounted in the midline by a dorsal projection, the spinous process. The arch is attached to the dorsolateral aspects of the body by two stout pillars, the pedicles.The typical vertebrae consists of two major components: a roughly cylindrical ventral mass of cancellous bone, the body and the dorsal vertebral arch.The gross anatomic appearance is one of cervical lordosis, thoracic kyphosis, and lumbar lordosis.Seven cervical, 12 thoracic, and five lumbar vertebrae compose the movable presacral spine five fused segments form the sacrum with four or five irregular ossicles caudal to the sacrum forming the coccyx The spinal column typically consist of 33 vertebrae.
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