UAMS Department of Neurobiology and Developmental Sciences - Bones of the Back Region

Gross Anatomy


Bones of the Back Region - Listed in Superior to Inferior Order

Bone Structure Description Notes

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

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


Some of the material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest and Jaye Schlesinger
Published by ILOC, Inc., New York. Copyright 1995.

The content of these tables has been edited for use in this course by Patrick W. Tank, Ph.D.
Copyright 2009, Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences.
Unauthorized use is prohibited.



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