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Chapter 7
Vertebral Column/Thoracic Cage
Vertebral Column
• Location:
– Forms the vertical axis of the skeleton
• General Structure:
– Composed of vertebrae
– Vertenrae are separated by masses of fibrocartilage called
intervertebral discs
– Each intervertebral disc is connected to one another by
ligaments
• Functions:
– Supports the head and trunk
– Protects the spinal cord, which passes through the
vertebral canal (formed by openings in the vertebrae)
Vertebral Column
• Number of bones in an infant skeleton:
– 33 bones
• Number of bones in an adult skeleton:
– 26 bones
• Five bones are fused into the sacrum
• Four bones are fused to form the coccyx (tailbone)
Vertebral Column
• Curvatures:
– Thoracic curvature
• Concave anteriorly
• Primary curve
– Sacral curvature
• Concave anteriorly
• Primary curve
– Cervical curvature
• Convex anteriorly
• Secondary curve
– Develops when a baby begins to hold
up its head
– Lumbar curvature
• Convex anteriorly
• Secondary curvature
– Develops when a child begins to stand
Typical Verterbra
• Body
– Drum-shaped
– Forms the thick,
anterior portion of the
bone
– Longitudinal rows of
bodies support the
weight of the head and
trunk
Typical Vertebrae
• Intervertebral discs
– Separate adjacent vertebrae
– Fastened to the roughened upper
and lower surfaces of the vertebral
bodies
– Soften forces (such as from walking
and jumping) that might fracture
the vertebrae or injure the brain
Typical Vertebra
• Anterior longitudinal ligaments
– Join adjacent vertebrae on the anterior surface
• Posterior longitudinal ligaments
– Join adjacent vertebrae on the posterior surface
Typical Vertebrae
• Vertebral Foramen
– Opening through which the spinal cord passes
Typical Vertebrae
• Vertebral Arch
– Surrounds the vertebral foramen
– Formed by:
• Pedicles
– Two short stalks that project posteriorly from each vertebral body
to form the sides of the vertebral foramen
• Spinous process
– Posterior projection formed by the fusion of two plates called
laminae
– Serves as an attachment for various ligament sand muscles
Typical Vertebrae
• Transverse process
– Projects laterally and posteriorly between the
pedicles and laminae
– Serves as an attachment for various ligament sand
muscles
Typical Vertebrae
• Superior articulating process
– Projects upward from each vertebral arch
– Has cartilage-covered facets by which each vertebrae
is joined to the one above it
• Inferior articulating process
– Projects downward from each vertebral arch
– Has cartilage-covered facets by which each vertebrae
is joined to the one above it
Typical Vertebrae
• Intervertebral foramina
– Formed by aligning notches on the lower surfaces
of the vertebral pedicles
– Provide passageways for spinal nerves that pass
between adjacent vertebrae and connect to the
spinal cord
Cervical Vertebrae
• Seven vertebrae that form the neck
– Smallest of the vertebrae
– Have the densest bone tissues
Cervical Vertebrae
• Special features:
– Transverse processes have transverse foramina,
which serve as passageways for arteries leading to
the brain
– Spinous processes of the 2nd through 6th cervical
vertebrae are forked (bifid) to provide
attachments for muscles
– Spinous process of the 7th cervical vertebra is
longer and called the vertebra prominens
Cervical Vertebrae
• 1st cervical vertebra is called the
atlas and supports the head
– Hardly has a body or spine
– Appears as a bony ring with two
transverse processes
– Has two kidney-shaped facets on its
superior surface that articulate with
the occipital condyles
• 2nd cervical vertebra is called the
axis
– Has a toothlike process called the
dens, or odontoid process that
projects upward and into the ring of
the atlas
• As the head turns from side to side the
atlas pivots around the dens
Thoracic Vertebrae
• 12 vertebrae below the cervical vertebrae
• Special features:
– Transverse processes project posteriorly at sharp angles
– Spinous processes are long and pointed and slope
downward
– Bodies have facets on each side that articulate with ribs
– Beginning with the third thoracic vertebra, each vertebra
increases in size to bear the increasing load of body weight
Lumbar Vertebrae
• 5 vertebrae in the small of the back
• Special Features
– Have larger and stronger bodies than vertebrae above
them as they have to support more weight
– Have thinner transverse processes that project
laterally
– Have short thick spinous processes that project
posteriorly and nearly horizontally
Sacrum
• Consists of 5 vertebrae that gradually fuse
together between the ages of 18 and 30
• Forms the posterior wall of the pelvic cavity
• Special Features:
Sacrum
– Spinous processes are fused to form a ridge of tubercules
called the median sacral crest
– Joined to the coxae of the pelvis at its auricular surfaces by
fibrocartilage of the sacroiliac joints
– The upper anterior margin of the sacrum (or the first sacral
vertebra) is called the sacral promontory
– Posterior sacral foramina are located to the sides of the
tubercules and allow nerves and blood vessels to pass through
– Vertebral foramina of the sacral vertebrae form the sacral
canal which opens at the tip of the sacrum (called the sacral
hiatus)
• Opening exists because the laminae of the last sacral vertebrae are not
fused
– Four pairs of anterior sacral foramina are located on the
ventral surface and allow passageways for nerves and blood
vessels
Coccyx
• Tailbone
• Usually consists of 4 vertebrae that fuse by
the 25th year.
• Cushions the force of sitting
• Attached to the margins of the sacral hiatus by
ligaments
Thoracic Cage
• Includes the ribs, the thoracic vertebrae, the
sternum, and the costal cartilages (attach ribs
to sternum)
• Functions:
– Support the shoulder girdle and upper limbs
– Protect the viscera in the thoracic and abdominal
cavities
– Play a role in breathing
Ribs
• Usual number is 24 (one pair attached
to each of the 12 thoracic vertebrae)
– Some people can develop extra ribs
associated with the cervical or lumbar
vertbrae
• True ribs (vertebrosternal ribs)
– First seven rib pairs
– Join the sternum directly by costal
cartilage
• False ribs (vertebrochondral ribs)
– Remaining five pairs
– Cartilages of the upper three pairs of false
ribs join the cartilage of the 7th rib
– The last two pairs have no attachment to
the sternum, so they are called floating
ribs (or vertebral ribs)
Ribs
• A typical rib has a long slender shaft
which curves around the chest and
slope downward
• An enlarged head is located at the
posterior end and articulates with a
facet on the body of its own
vertebra and the next highest
vertebra
• Neck of the rib is flattened, lateral
to the head, where ligaments
attach
• A tubercle that is close to the head
of the rib articulates with the
transverse process of the vertebra
Ribs
• Costal cartilages are composed of hyaline
cartilage and are attached to the anterior ends
of the ribs (and contour in line with them
toward the sternum)
Sternum
• Breastbone
• Flat elongated bone located along the midline in
the anterior portion of the thoracic cage
• Develops in three parts:
– An upper manubrium
• The manubrium usually remains as a separate bone until
middle age or later when it fuses to the body of the sternum
– A middle body
– A lower xyphiod process that projects downward
• The xiphoid process begins as a piece of cartilage, slowly
ossifies, and fuses to the body of the sternum by middle age
• The sides of the manubrium and the body are
notched where they articulate with costal cartilage
• The manubrium also articulates with the clavicles
by facets on its superior border