Osteology of the vertebrae

1. OSTEOLOGY OF THE VERTEBRAE
Structure of a typical Vertebra
Vertebrae have a common basic shape that changes in
the different segments of the spinal column to adapt to
their various static needs.
Every vertebra with the exception of the first cervical
(atlas, C1) vertebra has: Parts:
 Vertebral body (corpus vertebrae), which is
the anterior expanded part of the vertebra.
 vertebral arch(arcus vertebrae),located
posteriorly to the body.It is bounded by the lamina arcus
vertebrae and the pediculus arcus vertebrae.
 Vertebral foramen,foramen
vertebrale.The vertebral body and arch enclose the
vertebral foramen. All the vertebral foramina together
form the vertebral canal, which houses the spinal cord.
Corresponding to the increasing load, the size of the
vertebrae increases from above down.
 Pedicle, Pediculus arcus vertebrae,the
portion of the vertebral arch situated anteriorly
between the body and transverse process as well as
between the superior and inferior vertebral notches.
 Lamina, Lamina arcus vertebrae (vertebralis),the
portion of the vertebral arch situated
posteriorly between the transverse process and
the spinous process.
Processes:
There are seven(7) processes extending from the
vertebral arch,four(4) of which are articular
processes,processus

2. articularis, two(2)transverse,processus
transversus and one(1) spinous,processus spinosus.
The body and transverse processes of the thoracic
vertebrae bear joint facets for the ribs. Every vertebral
arch at its origin from the vertebral body is marked
above and below by a notch (incisuravertebralis,
inferior and superior vertebral notch). The notches of
two adjoining vertebrae form the intervertebral
foramen,which transmits the spinal nerves.
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There are 7 cervical, 12 thoracic, 5 lumbar, 5
sacral and 4-5 coccygeal vertebrae. Each of these
vertebral groups corresponds to a region of the vertebral
column.Vertebral column contains 33-34 vertebrae in
total.
CERVICAL VERTEBRAE
The seven cervical vertebrae form a flexible framework
for the neck and support the head. The bone tissue of
cervical vertebrae is more dense than that found in the
other vertebral regions and, except for those in the

3. coccygeal region, the cervical vertebrae are smallest.
Cervical vertebrae have features which make
them unique from other vertebrae.These features are :
 Large vertebral foramen. Because of this feature,
the spinal cord is safest in the cervical vertebrae.
 the presence of a transverse foramen,foramen
transversarium in each transverse process.The vertebral
arteries and veins pass through this opening as they
contribute to the blood flow associated with the brain.
 Cervical vertebrae C2–C6 generally have a bifid,
or notched, spinous process. The bifid spinous processes
increase the surface area for attachment of the strong
nuchal ligament that attaches to the back of the skull.
 The first cervical vertebra has no spinous process.
 The process of C7 is not bifid and is larger than
those of the other cervical vertebrae.It can easily be
palpated. Therefore, it is sometimes called the vertebra
prominens.
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4. C7

The atlas (C1) is the first cervical, which
differs from all other vertebrae.It has no body, it appears
as a transverse ring composed of two arches(arcus
anterior et posterior atlantis) and two lateral
masses,massa lateralis atlantis.
The axis (C2) is the second cervical
vertebra. On the superior surface of its
body, the axis bears a thick vertical
process, the dens.The dens carries
theanterior and posterior articular
surfaces,and its apex.The dens
corresponds to the body of the axis during

5. during the developmental
process.
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clinical application:Muscle, bone, or ligament injury in
this portion of the spinal column is relatively common in
individuals involved in automobile accidents and sports
injuries. Joint dislocation occurs commonly between the
fourth and fifth or fifth and sixth cervical vertebrae,
where neck movement is greatest. Bilateral dislocations
are particularly dangerous because of the probability of
spinal cord injury. Compression fractures of the first
three cervical vertebrae are common and follow abrupt
forced flexion of the neck. Fractures of this type may be
extremely painful because of pinched spinal nerves.
THORACIC VERTEBRAE
Twelve thoracic vertebrae articulate with the ribs to
form the
posterior anchor of the rib cage. Thoracic vertebrae are
larger than cervical vertebrae and increase in size from
superior (T1) to

6. inferior (T12). Unique features of thoracic vertebrae
are:
 Each thoracic vertebra has a long spinous
process,which slops obliquely
downward.
 Facets (fovea) for articulation with the ribs.
 Round vertebral foramen.
 roughly heart shaped body(corpus).
THE LUMBAR VERTEBRAE.
The five lumbar vertebrae, vertebrae lumbales(L1-L5),
form the lumbar region of the vertebral column. They
are characterized by the following structural features:
 Body is large and bean-shaped.
 Spinous processes are flattened and oriented in the
sagittal direction.
 Long transverse processes.
 The external border of the superior articular process
has amamillary process.

7. A laminectomy is the surgical removal of the spinous processes and their supporting
vertebral laminae in a particular region of the vertebral column. A laminectomy may be
performed to relieve pressure on the spinal cord or nerve root caused by a blood clot, a
tumor, or a herniated (ruptured) disc. It may also be performed
on a cadaver to expose the spinal cord and its surrounding meninges.
THE SACRAL VERTEBRAE
The wedge-shaped sacrum provides a strong foundation
for the pelvic girdle. It consists of four or five sacral
vertebrae that become fused after age 26. The sacrum
has an extensive auricular
surface on each lateral side for the formation of a
slightly
movable sacroiliac (sak''ro-il'e-ak) joint with the ilium of
the

8. hip. A median sacral crest is formed along
the dorsal surface
by the fusion of the spinous processes. Posterior sacral
foramina
on either side of the crest allow for the passage of nerves
from
the spinal cord. The sacral canal is the tubular cavity
within the
sacrum that is continuous with the vertebral canal.
Paired superior
articular processes, which articulate with the fifth
lumbar
vertebra, arise from the roughened sacral tuberosity
along the
posterior surface.
The smooth pelvic surface of the sacrum forms the
posterior surface of the pelvic cavity. It has four
transverse lines denoting
the fusion of the vertebral bodies. At the ends of these
lines are the paired pelvic foramina (anterior sacral
foramina).
The superior border of the anterior surface of the
sacrum, called
the sacral promontory, is an important obstetric
landmark for pelvic measurements.

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THE COCCYX
The triangular coccyx (“tailbone”) is composed of three to
five fused coccygeal vertebrae. The first vertebra of the fused
coccyx has two long coccygeal cornua, which are attached by
ligaments to the sacrum. Lateral to the cornua are
the transverse processes.
clinical application:When a person sits, the
coccyx flexes anteriorly, acting as a shock
absorber. An abrupt fall on the coccyx,
however, may cause a painful subperiosteal
bruising, fracture, or fracturedislocation of the

10. sacrococcygeal joint. An especially difficult
childbirth can even injure the coccyx of the
mother. Coccygeal trauma is painful and may
require months to heal.
THE VERTEBRAL COLUMN AS A WHOLE
The vertebral column consists of a series of irregular bones
called
vertebrae, separated from each other by fibrocartilaginous
intervertebral discs. Vertebrae enclose and protect the spinal
cord,support the skull and allow for its movement, articulate
with the rib cage, and provide for the attachment of trunk
muscles. The
intervertebral discs lend flexibility to the vertebral column
and absorb vertical shock.The vertebral column has a length
of about 70 cm and it accounts for about 25% of the length of
a human.
The vertebral column (“backbone”) and the spinal cord of
the
nervous system constitute the spinal column. The vertebral
column has four functions:
1. to support the head and upper extremities while permitting
freedom of movement;
2. to enable bipedalism;
3. to provide attachment for various muscles, ribs, and
visceral
organs; and
4. to protect the spinal cord and permit passage of the
spinal nerves.
The vertebral column is typically composed of 33
individual vertebrae, some of which are fused. There are 7
cervical, 12 thoracic, 5 lumbar, 3 to 5 fused sacral, and 4 or 5

11. fused coccygeal vertebrae; thus, the adult vertebral column
is composed of a total of 26 movable parts. Vertebrae are
separated by fibrocartilaginous intervertebral discs and are
secured to each other by interlocking processes and binding
ligaments. This structural arrangement permits only limited
movement between adjacent vertebrae but extensive
movement for the vertebral column as a whole. Between the
vertebrae are openings called intervertebral foramina that
allow passage of spinal nerves. When viewed from the side,
four curvatures of the vertebral column can be identified. The
cervical, thoracic, and lumbar curves are identified by the type
of vertebrae they include. The pelvic curve (sacral curve) is
formed by the shape of the sacrum and coccyx. The curves of
the vertebral column play an important functional role in
increasing the strength and maintaining the balance of the
upper part of the body; they also make possible a bipedal
stance.
The four vertebral curves are not present in an infant.
The cervical curve begins to develop at about 3 months as the
baby begins holding up its head, and it becomes more
pronounced as the baby learns to sit up. The lumbar curve
develops as a child begins to walk. The thoracic and pelvic
curves are called primary curves because they retain the shape
of the fetus.The cervical and lumbar curves are called
secondary curves because they are modifications of the fetal
shape.
THE CURVATURES OF THE VERTEBRAL
COLUMN The vertebral column possesses the following
curvature:
 Lordoses - anterior curvatures,present in the cervical and
lumbar regions(cervical and lumbar lordoses).

12.  Kyphosis - posterior curvatures, present in the
thoracic and sacral regions(thoracic and sacral kyphosis).
The curvatures are associated with the upright body
posture in humans. They absorb shocks placed on the
vertebral column, aid in balance maintenance and increase the
thoracic and pelvic cavities. In the thoracic region, there is a
slight curvature to the right( a physiological scoliosis) caused
by a well developed right upper limb.

13. Kamal Umar Labaran
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