![]() ![]() (a) At 4 months, the anterior ossification center is in isolation ( red arrowheads) because of the incompletely ossified neurocentral synchondroses ( red arrows). Axial computed tomographic images of C1 at 4 months, 20 months, 5 years, and 9 years of age. 24.2 Development of C1 and C2, axial views. The articulation of the atlas with the occipital condyles allows vertical motion of the head (e.g., nodding of the head) ( Fig. These lateral masses articulate with the occipital condyles, and because the C1 vertebra supports the cranium, it is sometimes referred to as the atlas (derived from the name of Atlas, the Greek god who supported the world on his back). The ring has an anterior and posterior neural arch, with two lateral masses. The first cervical vertebra, C1, does not contain a vertebral body, and represents a ring. The first two cervical vertebrae have unique morphologic and functional characteristics. From Atlas of Anatomy, © Thieme 2012, Illustrations by Karl Wesker. Diagrams showing the differences in sagittal alignment of the vertebral column in (h) infancy and (i) in adulthood. 24.1gi ( continued) (g) Artist’s drawing of a midsagittal section of the bones and ligaments of the skull base, craniocervical junction, and cervical spine. (f) Anatomic drawing of a typical lumbar vertebra from a lateral projection. (e) Anatomic drawing of a typical lumbar vertebra from a superior projection. ![]() (d) Anatomic drawing of a typical thoracic vertebra from a lateral projection. (b) Anatomic drawing of a typical cervical vertebra from a lateral projection (c) Anatomic drawing of a typical thoracic vertebra from a superior projection. 24.1af (a) Anatomic drawing of a typical cervical vertebra from a superior projection. (It is a satisfaction in pediatric neuroradiology to almost never have to describe neural foraminal stenosis, except at the apex of a severe scoliotic curvature and in several other rare situations.) The vertebrae have laterally directed transverse processes that arise anterior to the facets in the cervical and lumbar spine and posterior to the facets in the thoracic spine ( Fig. Beneath the pedicles of the neural arch are the neural foramina, through which nerve-root sleeves project. Posterior to that are medially directed laminae that come together to form the posteriorly directed spinous processes. The posterior neural arch consists of two pedicles that extend posteriorly to the superior and inferior articulating facets. The articulating vertebrae have a vertebral body and a posterior neural arch. Also, although the coccyx has four osseous segments, there is only one coccygeal nerve. At the cervicothoracic junction is a C8 nerve root, although there is no C8 vertebra. In the cervical spine, the C2–C3 neural foramen carries the C3 nerve root, and in the thoracic spine (as in the lumbar and sacral regions) the T1–T2 neural foramen carries the T1 nerve root. At each vertebral level are right and left nerve roots that emanate from the neural foramen. Throughout the articulating portions of the vertebral column, the vertebrae are separated from one another by fibrocartilagenous intervertebral disks. There are also variations in the number of ribs, including occasional cervical ribs at C7, absent ribs at T12, or rudimentary ribs at L1. The morphology of the coccyx is highly variable, and there are often transitional vertebrae at the lumbosacral junction, typically a sacralized (or hemisacralized) L5 vertebra or a lumbarized (or partly lumbarized) S1 vertebra. The vertebral column consists of 24 articulating vertebrae, including 7 cervical (C1–C7), 12 thoracic (T1–T12), and 5 lumbar vertebrae (L1–L5), and 9 fused and relatively immobile vertebrae, including 5 sacral (S1–S5) and 4 coccygeal (Cx1–Cx4) segments. In addition to the structure and protection provided by the bones of the vertebral column, the fibrocartilagenous intervertebral disks provide the ability for movement. The vertebral column also serves to protect the spinal cord, and is a defining anatomic feature of higher-order life forms. The vertebral column is the central supportive structure of the body, linking the skull base to the pelvis, with the ribs and extremities connected directly to the periphery of the column or connected indirectly to it through other bones, such as the shoulder or pelvic girdle. ![]()
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