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74

at their joint surfaces. This is due to the fact that the fi rst two cervical vertebrae, the atlas and axis, have forms

that differ signifi cantly from the remaining fi ve vertebrae in the series. These differences arise as they become

modifi ed to provide the support and movement of the skull. The remaining cervical vertebrae show a lesser

degree of mobility and have more uniform shapes. With few exceptions, the cervical vertebrae can be readily

distinguished by the presence of a foramen in their transverse processes.

There are seven cervical vertebrae, which are the vertebrae with the greatest variation in shape. They form a

delicate column of bones having a wide range of mobility

Cervical Vertebrae

 1 Vertebral body

 2 Pedicle

 3 Lamina

 4 Superior vertebral notch

 5 Inferior vertebral notch

 6 Vertebral foramen

 7 Spinous process

 8 Transverse process

 9 Superior articular process/facet

10 Inferior articular process/facet

 11 Transverse foramen

12 Anterior tubercle of costal process

13 Posterior tubercle of costal process

14 Lateral mass

15 Anterior arch

16 Anterior tubercle of anterior arch

17 Facet for dens

18 Posterior arch

19 Posterior tubercle of posterior arch

20 Groove for vertebral artery

21 Dens

22 Anterior articular facet of dens

Typical cervical vertebra

Superior view, anterior at bottom

Typical cervical vertebra

Lateral view, anterior at right

Typical cervical vertebra

Anterior view, superior at top Typical cervical vertebra

Posterior view, superior at top

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Atlas, 1st cervical vertebra

Superior view, anterior at bottom

Atlas, 1st cervical vertebra

Lateral view, anterior at right

Atlas, 1st cervical vertebra

Anterior view, superior at top

Atlas, 1st cervical vertebra

Posterior view, superior at top

Axis, 2nd cervical vertebra

Superior view, anterior at bottom

Axis, 2nd cervical vertebra

Lateral view, anterior at right

Axis, 2nd cervical vertebra

Anterior view, superior at top

Axis, 2nd cervical vertebra

Posterior view, superior at top

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76

at its junction with the lumbar vertebrae, the thoracic region is the least mobile region of vertebral column. In

addition to articulating with each other, the thoracic vertebrae also articulate with the ribs. Additionally, the laminae

and spines of these vertebrae project inferiorly to overlap the next vertebra below. This suite of characters

produces a strong imbricated column of bone that forms the impressive thoracic rib cage. Because of their

association with the ribs, the thoracic vertebrae are readily identifi ed by the costal articular facets, which are

present on the bodies and transverse processes.

The thoracic portion of the vertebral column, consisting of

the twelve thoracic vertebrae, get progressively larger

from the cranial end to the caudal end of the series. Except

Thoracic Vertebrae

 1 Vertebral body

 2 Pedicle

 3 Lamina

 4 Superior vertebral notch

 5 Inferior vertebral notch

 6 Spinous process

 7 Transverse process

 8 Superior articular process/facet

 9 Inferior articular process/facet

10 Superior costal facet

 11 Inferior costal facet

12 Transverse costal facet

Thoracic vertebra

Superior view, anterior at bottom Thoracic vertebra

Lateral view, anterior at right

Thoracic vertebra

Anterior view, superior at top Thoracic vertebra

Posterior view, superior at top

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77

size and lack of transverse foramina and costal facets are their diagnostic features. They form a strong column

of support at the base of the vertebral column. The articular processes of the lumbar vertebrae are robust and

have their facets oriented in the sagittal plane to provide for the fl exion and extension movements characteristic

of the lumbar vertebral column. They have thick pedicles arising from the superior aspect of the vertebral body.

The laminae are thick and short and project posteriorly to unite as thick, quadrilateral spinous processes. The

vertebral bodies have a large elliptical shape when viewed from above.

There are fi ve lumbar vertebrae that form the lumbar portion

of the vertebral column. The mobile vertebrae of this region

are the largest of the true or mobile vertebrae. Their large

Lumbar Vertebrae

 1 Vertebral body

 2 Pedicle

 3 Lamina

 4 Superior vertebral notch

 5 Inferior vertebral notch

 6 Spinous process

 7 Transverse process (costal process)

 8 Superior articular process/facet

 9 Inferior articular process/facet

10 Accessory process (morphological transverse process)

 11 Mammillary process

Lumbar vertebra

Superior view, anterior at bottom

Lumbar vertebra

Lateral view, anterior at right

Lumbar vertebra

Posterior view, superior at top

Lumbar vertebra

Anterior view, superior at top

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78

tened apex inferiorly. It is concave anteriorly and convex posteriorly. The lateral margins of the triangle are widest

superiorly where the bone articulates with the two ilia. Forming the large basal portion of the vertebral column,

the bone wedges between the two os coxae to form the posterior element of the pelvic skeleton. Its ventral surface, smoother than the rough dorsal surface, forms the posterior wall of the pelvis. Within this triangular mass

of bone is a hollow sacral canal. This canal opens through foramina onto the ventral and dorsal surfaces of the

bone. It forms a large oval surface superiorly that articulates with the fi fth lumbar vertebra and a smaller oval

facet at its apex for articulation with the coccyx.

 The coccyx is the terminal end of the vertebral column. It is a triangular bone that forms from the fusion

of three to fi ve vertebral segments, most commonly from four fused vertebrae. The superior surface of the fi rst

segment’s body forms an oval articular surface with the inferior surface of the fi fth sacral segment.

The sacrum is a large triangular-shaped mass that

forms from the fusion of fi ve vertebrocostal segments.

The base of the triangle is superior and tapers to a fl atSacrum and Coccyx

 1 Promontory

 2 Ala or wing

 3 Superior articular process

 4 Auricular surface

 5 Sacral tuberosity

 6 Pelvic surface

 7 Transverse ridges

 8 Anterior sacral foramina

 9 Posterior sacral foramina

10 Median sacral crest

 11 Intermediate sacral crest

12 Lateral sacral crest

13 Sacral cornu

14 Sacral canal

15 Sacral hiatus

16 Apex

17 Coccygeal cornu

Sacrum and coccyx

Lateral view, anterior at right

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79

Sacrum and coccyx

Anterior view, superior at top

Sacrum and coccyx

Posterior view, superior at top

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80

twelve thoracic ribs are named ribs, there are in reality ribs at every vertebral level. The cervical, lumbar,

sacral, and coccygeal ribs fuse to their corresponding vertebrae to contribute to the formation of the transverse process. The ribs can be divided into two groups — true ribs and false ribs. The last two false ribs are

called fl oating ribs. True ribs, ribs one through seven, are those that have their costal cartilages attached

directly to the sternum. False ribs, ribs eight through twelve, have costal cartilages that do not attach directly

to the sternum. The costal cartilage of each of the fi rst three false ribs attaches to the cartilage of the rib

superior to it. The last two false ribs do not attach to other ribs and are therefore called fl oating ribs.

There are twelve paired ribs, a pair for each of the twelve thoracic vertebrae. The ribs unite the

thoracic vertebrae to the sternum via costal cartilages to form the thoracic skeleton, a fl exible,

bony wall that protects thoracic viscera and facilitates respiratory function. Although only the

Ribs

Left sixth rib

Posterior view, superior at top

Ribs and thoracic vertebra

Superior view, posterior at top

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