Download Reem A Axial Skeleton

Human Anatomy,
First Edition
McKinley & O'Loughlin
Chapter 7 Lecture Outline:
Axial Skeleton
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Skeletal System
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The bones of the skeleton form an internal
framework to support soft tissues, protect vital
organs, bear the body’s weight, and help us move.
Typically, there are 206 bones in an adult skeleton,
although this number varies in some individuals.
A larger number of bones are present at birth, but
the total number decreases with growth and maturity
as some separate bones fuse.
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Skeletal System
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The axial skeleton is composed
of the bones along the central
axis of the body,
1.
the skull
2.
the vertebral column
3.
the thoracic cage
4.
Hyoid
The appendicular skeleton
consists of the bones of the
appendages
1.
upper and lower limbs
2.
the bones that hold the
limbs to the trunk of the
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The Skull
1. Cranial bones form the
rounded cranium, which
completely surrounds
and encloses the brain.
2. Facial bones form the
bones of the face. They
also
• protect the entrances
to the digestive and
respiratory systems as
well as
• provide attachment
sites for facial muscles
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The Mandible
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The lower jaw is
formed by the
mandible.
The prominent
“chin” of the
mandible is called
the mental
protuberance.
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Cavities of
The Skull
– The largest cavity
is the cranial
cavity, which
encloses,
cushions, and
supports the brain.
– The skull also has
several smaller
cavities, including
the orbits (eye
sockets), the oral
cavity (mouth), the
nasal cavity, and
the paranasal
sinuses.
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Cavity (space) in bone.
F= Frontal sinuses;
E=Ethmoid sinuses;
M=Maxillary sinuses
• the maxillary sinuses, are
under the eyes, in the
maxillary bones.
• the ethmoidal sinuses,
between the nose and the
eyes.
• the sphenoidal sinuses, in
the sphenoid bone.
behind the ethmoids
(sphenoidal sinuses
• the frontal sinuses,
superior to the eyes, in
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the frontal bone.
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Markings of the Skull
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Numerous bone markings
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canals
fissures
foramina
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passageways for blood vessels and nerves
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Foramen – Opening or Cavity
that provides a passageway for
nerves or blood vessels.
Foramen transversarium in
the cervical vertebrae
Foramen obturator in the
Os Coxa (hip)
Skull Base Anatomical Landmarks:
Foramen magnum
Fissure – Narrow slit.
The slits you see are the Superior Orbital
Fissures in the Eye Socket
Fontanels
• The regions between the
cranial bones are thickened,
fibrous membrane remnants
that are not yet ossified.
• Sometimes referred to as
the “soft spots” on a baby’s
head.
• They close by 15 months of
age.
• When a baby travels
through the birth canal, the
cranial bones overlap at
these fontanels, in order to
ease the baby’s passage.
• Newborns frequently have a
“cone-shaped” head due to
this temporary deformation.
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(craniosynostosi
s) of the lambdoid
suture. Notice the
swelling on the
right side of the
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head
Sutures of the Skull
• Sutures are immovable
fibrous joints that form the
boundaries between the
cranial bones.
• Dense regular connective
tissue seals cranial bones
firmly together at a suture.
• Allow the cranium to grow
and expand during
childhood.
• In adulthood, when cranial
growth has stopped, the
sutures fuse and are
obliterated(destroyed)
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The sphenoid bone is an
unpaired cranial bone situated
at the front middle of the skull
in front of the temporal bone
and basilar part of the occipital
bone.
The sphenoid bone is one of the
seven bones that articulate to
form the orbit.
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Insert Fig. 7.9 superior view of skull
The sphenoid bone has median portion, known as the body of
sphenoid bone, containing the sella turcica, which houses the
pituitary gland as well as the paired paranasal sinuses, the
sphenoidal sinuses
two greater wings and two lesser wings.
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The sphenoid bone
shape somewhat
resembles that of a
butterfly or bat with
its wings extended
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The
ethmoid
bone from
Greek
ethmos,
"sieve") is a
bone in the
skull that
separates
the nasal
cavity from
the brain. It
is located at
the roof of
the nose,
between the
two orbits.
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The ethmoid has three parts:
the cribriform plate, the
ethmoidal labyrinth, and the
perpendicular plate
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part of the
lateral wall and
floor of the orbit
the zygomatic
bone
(cheekbone,
malar bone) is a
paired bone which
articulates with the
maxilla, the
temporal bone, the
sphenoid bone and
the frontal bone.
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The vomer is located in the
midsagittal line, and articulates
with the sphenoid, the ethmoid,
the left and right palatine
bones, and the left and right
maxillary bones. The vomer
forms the posterior part of the
nasal septum.
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Palatine bone
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upper palate of mouth or maxilla:two halves that are fused at
the intermaxillary suture to form the upper jaw.
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the mandible, lower jaw or
jawbone
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Sinuses
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Have a mucous lining that helps to
humidify and warm inhaled air.
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Cause these skull bones to be lighter.
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Provide resonance to the voice.
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The following bones
Superior margin: frontal bone
Inferior margin: maxilla, palatine and zygomatic
Medial margin: frontal, lacrimal and ethmoid
Lateral margin: zygomatic and sphenoi
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Auditory Ossicles

Three tiny ear bones called auditory
ossicles are housed within the temporal
bone.
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the malleus
the incus
the stapes
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Hyoid Bone
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Slender, curved bone located
inferior to the skull between
the mandible and the larynx
(voice box).
Does not articulate with any
other bone in the skeleton.
Serves as sites for
attachment for tongue and
larynx muscles and
ligaments.
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The Vertebral Column
• Composed of 26 bones,
including
– 24 individual vertebrae and
the
– fused vertebrae that form
both the sacrum and the
coccyx
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C- Vertebral column.
•
•
•
•
•
•
Vertebral column
consists of vertebrae
Cervical vertebrae,
they are 7 in number,
Thoracic vertebrae,
they are 12
Lumber vertebrae,
they are 5 in number
Sacral vertebrae
(sacrum), 5 fused
Coccygeal vertebrae
3 or 4 united
The vertebral column has
several functions:
1. Providing vertical
support for the body
2. Supporting the weight
of the head
3. Helping to maintain
upright body position
4. Helping to transfer
axial skeletal weight
to the appendicular
skeleton of the lower
limbs
5. Housing and
protecting the delicate
spinal cord and
providing a
passageway for spinal
nerves connecting to
the spinal cord
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Between each vertebra
is an intervertebral
disk, which acts as a
shock absorber.
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Atlas: the 1st cervical vertebra
has no body, and this is due to the fact that the body of
the atlas has fused with that of the next vertebra
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The movement of shaking or rotating the head left and
right happens almost entirely at the joint between the
atlas and the axis, the atlanto-axial joint.
The movement of nodding the head takes place predominantly
through flexion and extension at the joint between the atlas and
the occipital bone, the atlanto-occipital joint.
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(sacrum 5 fused bodies united
by four intervertebral disk;
Coccygeal vertebrae (coccyx), triangular tail bone united with
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sacrum by intervertebral disk (embryonic tail).
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Three Main Spinal Curvature
Deformities
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Kyphosis is an exaggerated thoracic curvature that
is directed posteriorly, producing a “hunchback”
look.
Lordosis is an exaggerated lumbar curvature,
often called “swayback,” that is observed as a
protrusion of the abdomen and buttocks.
Scoliosis is an abnormal lateral curvature that
sometimes results during development when both
the vertebral arch and body fail to form, or form
incompletely, on one side of a vertebra.
 scoliosis is the most common spinal curvature
deformity.
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B- Thorax / (bony thorax).
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A.
B.
C.
Posterior View Of Ribs &
Articulating Vertebrae
The rib cage or consists of:
12 thoracic vertebral bodies
posteriorly,
12 pairs of ribs laterally
sternum (1) anteriorly.
Thoracic Cage
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Acts as a protective cage around vital organs, such
as the heart, lungs, trachea, and esophagus.
Provides attachment points for many muscles
supporting the pectoral girdles, the chest, the
neck, the shoulders, the back, and the muscles
involved in respiration.
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• Both males and females 12
pairs
– Ribs 1–7 are called true ribs.
At the anterior body wall, the
true ribs connect individually
to the sternum by separate
cartilaginous extensions
called costal cartilages.
– Ribs 8–12 are called false ribs
because their costal cartilages
do not attach directly to the
sternum. The costal cartilages
of ribs 8–10 fuse to the costal
cartilage of rib 7 and thus
indirectly articulate with the
sternum.
– The last two pairs of false ribs
(ribs 11 and 12) are called
floating ribs because they
have no connection with the
sternum.
Ribs
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