Medical Gross Anatomy
Anatomy Tables - Bones of the Back Region - Listed in Superior to Inferior Order
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Medical Gross Anatomy |
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| Bone | Structure | Description | Notes |
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occipital |
the bone forming the posterior surface of the skull | it articulates superolaterally with the parietal bones through the lambdoid suture, anteroinferiorly with the temporal bone and anteriorly with the body of the sphenoid bone | |
| external occipital protuberance | a low process on the external surface of the occipital bone in the midline | it is an attachment site for the ligamentum nuchae; the superior nuchal lines of the two sides meet in the midline at the external occipital protuberance; also known as: inion | |
| inferior nuchal line | a low ridge that runs transversely on the external surface of the squamous part of the occipital bone inferior to the superior nuchal line | it is an attachment site for deep neck muscles | |
| superior nuchal line | a low ridge that runs transversely on the external surface of the squamous part of the occipital bone | it is an attachment site the for the trapezius and splenius mm. | |
| occipital condyle | a low, wide projection from the inferior surface of the lateral part of the occipital bone | paired; it articulates with the atlas | |
| vertebra | one of a series of irregular bones that form the spine | a vertebra has two parts: the vertebral body and the vertebral arch; there are 33 vertebrae total: 7 cervical, 12 thoracic, 5 lumbar, 5 fused to form the sacrum, 4 coccygeal; features of a typical vertebra include: body, pedicles, transverse processes, laminae, articular processes, spinous process | |
| vertebral body | the largest part of the vertebra | it is shaped like a short cylinder; adjacent vertebral bodies articulate through a symphysis | |
| vertebral arch | the ring of bone formed by the paired pedicles and paired laminae of the vertebra | the transverse processes and spinous process are attached to the neural arch; the neural arch protects the spinal cord | |
| pedicle | short strong process that extends posteriorly from the posterolateral surface of the vertebral body | paired; it connects the body with the transverse process; it is marked by superior & inferior vertebral notches; | |
| transverse process | a lateral process the extends from the junction of the pedicle and the lamina of the vertebra | a site for muscle attachment and rib articulation | |
| lamina | a broad flat plats of bone located between the transverse process and the spinous process of the vertebra | paired; it is flattened markedly in the anteroposterior direction; ligamenta flava span the interval between the laminae of adjacent vertebrae | |
| articular processes | processed that project inferiorly and superiorly from the junction of the lamina and pedicle of the vertebra | two pair on each vertebra (superior and inferior); the superior articular processes of one vertebra articulate with the inferior processes of the adjacent vertebra through synovial joints | |
| intervertebral notch | a notch on the superior and inferior surface of the vertebral pedicle | the superior intervertebral notch of one vertebra combined with the inferior intervertebral notch of the adjacent vertebra forms the intervertebral foramen | |
| intervertebral foramen | an opening between the pedicles of adjacent vertebrae | adjacent intervertebral notches form the intervertebral foramen; an opening for passage of the spinal nerve | |
| vertebral canal | the opening formed by the combination of the body and the vertebral arch | it contains the spinal cord, meninges, epidural fat and the internal vertebral plexus of veins | |
| spinous process | a posterior midline process arising from the junction of the two laminae of the vertebra | it projects downward and inferiorly; it is an important site of muscle attachment; spinous processes of cervical vertebra 2-6 are bifid | |
| cervical vertebrae | the seven vertebrae of the neck | cervical vertebrae have the features of the typical vertebra plus all have transverse foramina (for passage of the vertebral artery); C2-C6 have bifid spinous processes; cervical vertebrae have relatively small bodies; several cervical vertebra are named: atlas, axis, vertebra prominens | |
| atlas (C1) | the first cervical vertebra |
it is called atlas in comparison the mythological Greek Titan Atlas, who bore the weight of the world on his shoulders; it has no vertebral body, only anterior & posterior arches; it articulates with the odontoid process of the axis |
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| axis (C2) | the second cervical vertebra | the odontoid process (dens) projects superiorly from its body; it articulates with the anterior arch of the atlas | |
| vertebra prominens | the seventh cervical vertebra | it has a long, non-bifid spinous process which is prominent at the nape of the neck, hence its name | |
| thoracic vertebrae | the 12 vertebrae associated with the thoracic region | thoracic vertebrae have the features of a typical vertebra plus they are characterized by long slender spines that project inferiorly; they have facets for articulation with ribs; thoracic vertebrae have bodies of intermediate size | |
| costal articular facet on the body | small smooth areas at the junction of the body and the vertebral arch | most thoracic vertebrae have 2 costal facets on each side (one superior and one inferior); the superior costal facet of one vertebra and the inferior costal facet of the adjacent vertebra both articulate with the head of the same rib; also known as demifacets | |
| costal articular facet on the transverse process | a small smooth area on the transverse process of the thoracic vertebra | it articulates with the articular facet on the tubercle of the rib | |
| lumbar vertebrae | the 5 vertebrae located in the lumbar region | lumbar vertebrae have the features of a typical vertebra plus they are characterized by short, blunt spines that project posteriorly; lumbar spines do not overlap making the lumbar level a good one for spinal tap; lumbar vertebrae are built strong and have the largest bodies of all vertebrae | |
| sacrum | a triangular bone that is the posterior skeletal element forming the pelvis | it is formed by 5 fused vertebrae; the sacrum and two os coxae bones form the pelvis | |
| anterior sacral foramina | an opening in the anterior surface of the sacrum | there are four pairs; each transmits the ventral primary ramus of the respective sacral spinal nerve; branches of the lateral sacral aa. enter the sacral canal through these openings | |
| posterior sacral foramina | an opening in the posterior surface of the sacrum | there are four pairs; each transmits the dorsal primary ramus of the respective sacral spinal nerve | |
| promontory | a projection of the superior part of the sacrum in an anterior direction | the body of the fifth lumbar vertebra sits on the sacral promontory and articulates with it through a symphysis | |
| sacral canal | the opening in the center of the sacrum | it is the continuation of the vertebral canal at sacral vertebral levels | |
| articular surface | the roughened area located on the lateral surface of the sacrum | this surface articulates with the ilium in the sacroiliac articulation | |
| body | the central portion of the sacrum | the body is equivalent to the bodies of the other vertebra | |
| base | the superior surface of the sacrum | the base of the sacrum articulates with the fifth lumbar vertebra through an intervertebral disk | |
| sacral hiatus | an opening in the posterior surface of the sacrum in the midline | it is a normal feature that results from the failure of fusion of the laminae of the fifth sacral segment (and sometimes the fourth) during development | |
| ala | the lateral portion of the sacrum | paired; it projects laterally from the body of the sacrum; it represents the fused costal and transverse processes of the first sacral vertebra | |
| coccyx | the most inferior portion of the vertebral column | the coccyx results from the fusion of the four coccygeal vertebrae; it may be a single bone or the first coccygeal vertebra may be separated from the other three; it articulates with the fifth sacral segment; coccygeal vertebrae are reduced in complexity, having no pedicles, laminae or spines |
| The material presented in these tables is
contained in the book: MedCharts Anatomy by Thomas R. Gest & Jaye Schlesinger Published by ILOC, Inc., New York Copyright © 1995, unauthorized use prohibited. |
The excellent editorial assistance of Dr. Pat Tank, UAMS is gratefully acknowledged. |
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| Copyright© 2000 The University of Michigan. Unauthorized use prohibited. |
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