| 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 |
