Vertebral column

Published on 11/03/2015 by admin

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Last modified 11/03/2015

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9 Vertebral column

The vertebral column usually consists of:

7 cervical vertebrae (movable)

12 thoracic vertebrae (movable)

5 lumbar vertebrae (movable)

5 sacral segments (fused)

4 coccygeal segments (fused to a variable extent).

A ‘typical’ vertebra

Insight

By learning the parts of a typical vertebra, the majority of the parts of the cervical, thoracic and lumbar vertebrae can be identified.

Main parts

Body –

cancellous bone covered with compact bone; anterior surface is convex.

Pedicles –

project back from the postero-lateral aspects of the body.

Laminae –

project back from the ends of the pedicles; fuse in the midline.

Vertebral arch –

formed by 2 pedicles and 2 laminae.

Vertebral foramen –

formed by the posterior aspect of the body and the vertebral arch. The vertebral foramina and intervertebral joints and ligaments form the vertebral canal, which transmits and protects the spinal cord, spinal nerve roots and meninges.

Transverse processes –

project laterally from the junction of the pedicles and laminae.

Spinous process –

projects backwards from the junction of the laminae.

Superior articular processes –

projections on the superior aspect of the vertebral arch at the junction of the pedicles and the laminae which carry the superior articular facets.

Inferior articular processes –

projections on the inferior aspect of the vertebral arch which carry the inferior articular facets.

Vertebral notches, superior and inferior –

formed between the body and the articular processes above and below the pedicles.

Intervertebral foramina –

formed by the vertebral notches, between the pedicles of adjacent vertebrae. Transmit the spinal nerves. Lie at an angle of 45° to the median sagittal plane and 0–15° to the horizontal.

Cervical vertebrae

3rd to 6th (typical) (Figs 9.1 and 9.2)

Features

Body –

small, oval in shape.

Lamina –

long and thin.

Vertebral foramen –

large and triangular (cervical enlargement).

Pedicles –

short, round, project laterally and backwards 45°.

Intervertebral foramen –

directed forwards and laterally.

Transverse processes –

carry the foramen transversarium for the vertebral arteries; these divide the processes into anterior and posterior roots, which end in small tubercles.

Superior articular facet –

faces upwards and backwards.

Inferior articular facet –

faces downwards and forwards.

Spinous process –

short and bifid (divided).

Radiographic appearances of the cervical vertebrae (Figs 9.3, 9.4, 9.5, 9.6 and Plate 6)

Fig. 9.3 Third to seventh cervical vertebrae: anteroposterior projection.

A–Angle of mandible

B–Larynx

C–Body of 5th cervical vertebra

D–Trachea

E–Spinous process of 7th cervical vertebra

F–Body of 1st thoracic vertebra

G–1st rib

H–Transverse process of 7th cervical vertebra

I–Spinous process

J–Level of vocal folds

K–Transverse process

L–Articular process.

(From Bryan 1996.)

Fig. 9.4 Cervical vertebrae: lateral projection.

1 – Anterior tubercle of atlas

2 – Odontoid process

3 – Mandible

4 – Body of 4th cervical vertebra

5 – Transverse process

6 – Body of 1st thoracic vertebra

7 – 1st rib

8 – Pedicle

9 – Spinous process of 7th cervical vertebra (vertebra prominens)

10 – Inferior articular process

11 – Superior articular process

12 – Lamina

13 – Spinous process of axis

14 – Posterior tubercle of atlas

15 – Occipital bone

16 – Atlanto-occipital joint.

(From Bryan 1996.)

Fig. 9.5 Cervical vertebrae: oblique anteroposterior projection.

A – Atlas

B – Spinous process of axis

C – Right intervertebral foramina

D – 1st thoracic vertebra

E – 2nd thoracic vertebra

F – 1st rib

G – Trachea

H – Mandible.

(From Bryan 1996.)

Fig. 9.6 Atlas and axis (C1 and C2): MR scan to cervical vertebrae.

A – Odontoid process

B – Body of axis (C2)

C – Spinal cord

D – Intervertebral disc

E – Posterior longitudinal ligament

F – Anterior longitudinal ligament

G – Vertebral body

H – Spinous process of 6th cervical vertebra

(From Bryan 1996.)

1st cervical vertebra (atlas) (Fig. 9.7)

Fig. 9.7 1st cervical vertebra (superior aspect).

A–Anterior tubercle

B–Superior articular facet

C–Foramen transversarium

D–Vertebral foramen

E–Posterior arch

F–Posterior tubercle

G–Groove for the vertebral artery

H–Transverse process

I–Facet for the odontoid process

J–Anterior arch.

Articulations

Superior articular facets with the occipital condyles to form the atlanto-occipital joints.

Inferior articular facets with the superior articular facets of the 2nd cervical vertebra to form the lateral atlanto-axial joints.

The facet on the anterior arch with the odontoid process of the 2nd cervical vertebra to form the median atlanto-axial joint.

Features

‘Ring-shaped’ with no body.

Anterior arch –

in the midline there is a projection called the anterior tubercle. On the posterior aspect is a facet for the odontoid process of the 2nd cervical vertebra.

Posterior arch –

in the midline there is a projection called the posterior tubercle, which represents a rudimentary spinous process. There is a wide groove behind the lateral masses for the vertebral arteries.

Vertebral foramen –

oval.

Lateral masses –

lie on either side of the vertebral foramen and carry the superior and inferior articular facets. On the medial aspect is a tubercle for the transverse ligament of the atlas.

Superior articular facets –

large and oval.

Inferior articular facets –

round and flat.

Transverse process –

long, assists with rotation of the head.

Foramen transversarium –

pierces the transverse process.

Ossification

Primary centres

3 centres:

lateral masses (1 per mass) appear 7th week of intrauterine life;

the masses fuse age 3–4;

anterior arch appears age 1.

Fuse together age 6–8.

2nd cervical vertebra (axis) (Figs 9.8 and 9.9)

Articulations

Superior articular facets with the inferior articular facets of the 1st cervical vertebra to form the lateral atlanto-axial joints.

Fig. 9.8 2nd cervical vertebra (axis) (anterior aspect).

A–Odontoid process (dens)

B–Facet for the anterior arch of the atlas

C–Superior articular facet

D–Foramen transversarium

E–Transverse process

F–Body

G–Inferior articular facet.

Fig. 9.9 2nd cervical vertebra (axis) (lateral aspect).

1 – Facet for the anterior arch of the atlas

2 – Superior articular facet

3 – Foramen transversarium

4 – Body

5 – Inferior articular facet

6 – Inferior articular process

7 – Lamina

8 – Spinous process

9 – Groove for the transverse ligament of the atlas

10 – Odontoid process (dens).

Inferior articular facets with the superior articular facets of the 3rd cervical vertebra to form the joints of the vertebral arches.

The odontoid process with the anterior arch of the 1st cervical vertebra to form the median atlanto-axial joint.

The body with the body of the 3rd cervical vertebra to form the intervertebral joint.

Features

Odontoid process (dens) –

projection on the upper aspect of the body. Has a facet for articulation with the anterior arch of the 1st cervical vertebra. Represents the body of the atlas.

Insight

Whiplash injuries can cause a fracture of the base of the odontoid process as this is the weakest part of the spine, movement of the head following injury can result in damage to the spinal cord.

Ossification

Primary centres

5 centres:

odontoid process – 2 centres appear 6th month intrauterine life.

odontoid centres fuse together before birth;

vertebral arch – 2 centres appear 7th–8th month intrauterine life;

body – age 4–5 months.

Secondary centres

2 centres:

odontoid process appears age 2, fuses age 12;

thin plate under the body appears at puberty.

Thoracic vertebrae

Bones and Joints A Guide for Students

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Vertebral column

3rd to 6th (typical) (Figs 9.1 and 9.2)

Radiographic appearances of the cervical vertebrae (Figs 9.3, 9.4, 9.5, 9.6 and Plate 6)

1st cervical vertebra (atlas) (Fig. 9.7)

2nd cervical vertebra (axis) (Figs 9.8 and 9.9)

Radiographic appearances of the upper cervical vertebrae (Figs 9.10, 9.11 and 9.12)

2nd to 8th (typical) (Figs 9.13 and 9.14)

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