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Main Anatomy Index
| The vertebral column
Last updated 30 March 2006
- The vertebral column forms the skeleton of the back and
the main part of the axial skeleton.
- It consists of 33 bones called vertebrae which articulate with each other an anterior
and posterior intervertebral joints. The vertebrae are
arranged into five regions, but only 24 of them are (7 cervical, 12 thoracic and 5 lumbar)
are movable. In adults, the five sacral vertebrae are fused to form the sacrum and the four coccygeal vertebrae are fused to form the coccyx.
- The movable vertebrae are also connected to each other by paired, posterior zygapophyseal joints (facet joints) between the articular
processes, and strong anterior and posterior longitudinal ligaments.
Normal Curvature of the
Vertebral Column (pp. 323, 326)
- Four curvatures are normally visible in the adult.
- The thoracic and sacral curvatures are concave anteriorly while the cervical and lumbar
curvatures are concave posteriorly.
- The thoracic and scaral curvatures are called primary curvatures
because they develop during the fetal period.
- The cervical and lumbar curvatures are called secondary curvatures
as they are not very obvious until after birth.
- The centre of gravity of the body is located just
anterior to the sacral promontory.
Typical Adult Vertebrae (pp.
327, 329, 331)
- A "typical" vertebrae is composed of two parts, a body
and a vertebral arch. Each part has a specific function.
Typical vertebrae vary in size and other characteristics from one region to another, and
to a lesser degree within each region.
Parts of a Typical Vertebrae
The body is anterior and the vertebral arch is posterior.
The Body (p. 329)
- This is the large, heavy, anterior part which has the
form of a short cylinder. It resembles a short long bone.
- Its function, like long bones, is to support weight.
- The bodies of the vertebrae, especially T4 inferiorly, becomes progressively larger in
order to bear progressively greater weight.
- Their superior and inferior surfaces are rough and flat, except for the smooth bony rims at their circumferences.
- A nutrient foramen pierces the anterior suface of the
body and there is a large foramen on the posteior surface for the exit of the basivertebral vein.
The Vertebral Arch (p. 329)
- The part encloses the vertebral foramen.
- The vertebral arch (neural arch), which is attached on each side of the body, protects
the neural tissues from injury.
- The arch if formed by two pedicles (L. little feet)
which projects posteriorly to meet two laminae (L. thin
plates). The laminae meet posteriorly to form the spinous process.
- Four articular processes and two transverse processes also arise from the vertebral
- The space enclosed the the body and the arch is the vertebral
- The succession of the vertebral foramina in the articulated vertebral column forms the vertebral canal, which contains the spinal
cord and its protective membranes (G. meninges), nerve roots and blood
- The pedicles of the vertebral arch are short stout
processes which are attached to the superior part of the body on each side. These project
posteriorly to meet the broad and flat laminae.
- Vertebral notches are formed by indentations of the
pedicles. The small notch superior to the pedicle, the superior
vertebral notch, varies in size at different levels fo the vertebral column.
The inferior vertebral notch is larger. When the two
vertebral articulate, the vertebral notches are adjacent to each other and form an almost
complete oval bony ring, the intervertebral foramen.
- The laminae of the vertebral arch are broad flat plates
of bone that extend posteromedially and slightly inferiorly from the pedicles. They
overlap the laminae of the vertebrae below.
- The two laminae form the roof of the vertebral foramen
where they unite in the median plane. The spinous process arises from their place of
- The laminae are rough on their superior and inferior borders where the ligamentum flava attach.
- The spinal roots, dorsal and ventral, in addition to
the spinal cord and meninges, are in the vertebral canal. The spinal
ganglia (dorsal root ganglia) are in the intervertebral foramina. The nerve
roots join each other at the external border of the intervertebral foramen to form a spinal nerve.
Seven Vertebral Processes (pp. 329, 331)
- There are level-like (the spinous and tranverse processes) and four are articular (the
- The spinous process of typical vertebrae project
posteroinferiorly, usually in the medial plane, from the place of union of the laminae.
They overlap the vertebrae below.
- These processes provide attachments for the interspinous and supraspinous ligaments and
- The transverse processes project posterolaterally and
slightly superiorly from the junctions of the pedicles and laminae.
- These processes act as levers and provide attachments
for the deep back muscles, helping them to increase their leverage on the vertebral
- The articular processes (zygapophyses) also arise from
the junctions of the pedicles and laminae.
- The superior articular processes project superior and the inferior processes inferiorly.
Each process has an articular facet.
- The articulation between the superior and inferior articular facets at the zygopophyseal (facet) joints helps to prevent anterior movement
of the superior vertebra on an inferior one, especially in the thoracic and lumbar
- The articular facets allow some flexion and extension as well as varying degrees of
lateral flexion and rotation.
Regional Characteristics of Vertebrae
|Region of Vertebrae Column
||Foramina transversaria, bifid spinous process.
||Facets on sides of bodies for articulation with ribs, heart
shaped bodies and circular vertebral foramina
||Massive bodies and sturdy laminae, largest of movable
vertebrae, absence of costal facets.
The Cervical Vertebrae (p. 331)
- These vertebrae are the smallest of the movable ones and form the bony
skeleton of the neck.
- Their distinctive feature is the oval foramen transversarium
or foramen of the transverse process. These foramina are smaller in C7 than those of the
other cervical vertebrae; occasionally they are absent.
- The vertebral arteries pass through the foramen transversarium
except those which transmit only small accessory vertebral veins.
- The vertebral foramen is large in the cervical vertebrae as it houses the cervical
enlargement for the spinal cord.
- Cervical vertebrae have the typical vertebral structure, except for C1 and C2.
- The spinous processes of C3 to 6 vertebrae are short and bifid (L. bifidus,
divided into two parts).
- The spinous process of C7 (vertebrae prominens) is very
- Another characteristic of cervical vertebrae is the almost equal size of their vertebral
- C1 and C2 are atypical vertebrae.
- C1, a ring-shaped bone, is called the atlas. It was named after Atlas,
the Titan who is depicted as supporting the Earth on his shoulders (C1 supports the
- The kidney-shaped, concave superior articular facets of C1 receive the occipital
- The atlas has not spinous process or body; it consists
of anterior and posterior arches, each of which has a tubercle and a lateral mass.
- There is a tubercle each on the medial surfaces of the superior articular processes for
the transverse ligament, which holds in place the dens of
- There is also a groove that runs from the foramen transversarium to posterior to the
anterior articular processes. This groove is for the vertebral artery as it winds around
and enters the skull through the foramen magnum.
- C2 is the strongest of the cervical vertebrae and is
called the axis because C1 carrying the skull rotates on
- C2 has two large flat bearing surfaces, the superior articular
facets, upon which the atlas rotates.
- Its distinguishing feature, however, is the blunt tooth-like dens (G. tooth) is held in
position by the transverse ligament of the atlas, which
prevents horizontal displacement of the atlas.
- C2 has a large bifid spinous process, which is the
first one that can be felt in the posterior groove of the neck (sometimes referred to as
the nuchal furrow).
- The reason that C1 and C2 vertebrae are so atypical is because part of the body of C1 is
incorporated into the body of C2
- The part of the body that remains with C1 is represented by the anterior arch.
- The part of the body of C1 that is added to C2 forms the dens.
- It rises perpendicularly from the superior surface of its body. It is the pivot around
which C1 (carrying the head) rotates.
The Thoracic Vertebrae (pp. 331-2)
- The characteristic feature of these bones are their costal facets
for articulation with the ribs. There is one or more facets on each side for the body for
articulation with the head of a rib, and one on each transverse process of the superior 10
vertebrae for the tubercle of the rib.
- Their spinous processes are long and slender and the
middle ones are directely inferiorly over the vertebral arches of the vertebrae inferior
- The middle four thoracic vertebrae are typical.
- The outline of their bodies from above is heart-shaped
and their vertebral foramen are circular.
- Sometimes an impression is visible on the left sides of the bodies of these vertebrae.
This is produced by the descending thoracic aorta.
- The articular facets are arranged such that they are the posterior part of an arc, with
the centre of the circle near the centre of the body of the vertebrae.
- T1 to T4 vertebrae have some feature of cervical vertebrae.
- T1 is atypical in that it has a long, almost horizontal spinous process which may be
nearly as prominent as that of the vertebrae prominens.
- T1 also has a complete costal facet on the superior edge of its body for the first rib
and a demifacet on its inferior edge which contributes to the articular surface for the
- T9 to T12 vertebrae are also atypical in that they have
tubercles similar to the lumbar vertebra.
Lumbar Vertebrae (p. 332)
- These bones are in the "small of the back" and their spinous processes are
visible when the vertebral column is flexed.
- They are distinguished by their massive bodies, sturdy
laminae, and the shickness of the lower trunk in the median plane.
- Their bodies viewed superiorly are kidney-shaped (reniform), and their vertebral
foramina vary from oval to triangular.
- The largest of all the movable vertebrae, L5, is characterised by its
stout transverse process.
- It is large responsible for the lumbosacral angle
between the lumbar region and sacrum. The body weight is transmitted from the massivle L5
vertebra to the base of the sacrum.
The Sacrum and Coccyx
Click here to go to The Sacrum