Download Bone Disorders and The Cranium

THE PARTS OF THE SKELETAL
SYSTEM
Parts of the Skeletal System
 Three are two main parts to
the skeletal system:
The axial skeleton made up of
skull, vertebral column, bony
thorax, and hyoid bone.
2. The appendicular skeleton
made up of the upper and
lower extremities, the
shoulder girdle and the pelvic
girdle.
1.
The Skull
 Consists of the cranium and the facial bones.
 The cranium houses and protects the brain.
 The facial bones hold and protect the eyes, forms
the nose and mouth areas.
 Altogether, there are 22 bones associated with
the skull.
The Cranium
 The back portion of the skull.
 Consists of 8 flat bones that fuse together.
 During infancy, the bones were held
together with fibrous membranes that
eventually ossified and left immovable
joints called sutures.
The Cranium
The Cranium
Frontal Bone
 Forms the forehead
 Includes the bony
projections under the
eyebrow and the
superior part of each
eye orbit.
Frontal Bone
Parietal Bones (2)
 Forms the superior and lateral walls of the
cranium.
 They meet at the superior midline of the skull
at the sagittal suture
 Meets the posterior edge of the frontal bone
to form the coronal suture
Parietal Bones
Sagittal Suture
Coronal Suture
Parietal
bone
(right)
Parietal
bone
(left)
Frontal Bone
Temporal Bones (2)
 Lie inferior to the parietal bones. Fuse with the
parietal bones at the squamous sutures.
Squamous
suture
Temporal
bone
Temporal
bone
Temporal Bones
 Have several important bone markings:
 1. external auditory meatus – the canal that leads
into the ear and eventually the ear drum
 2. styloid process – a needle-like projection
inferior to the external auditory meatus; for
muscle attachment
 3. zygomatic process – a bridge of bone that joins
with the cheekbone
External auditory
meatus
Styloid process
Zygomatic
process
Temporal Bones
 4. mastoid process – a rough projection posterior
and inferior to the external auditory meatus; an
attachment site for some neck muscles.
 5. jugular foramen – an opening at the junction of
the occipital and temporal bones; allows for the
jugular vein to pass through (drain the brain).
 6. carotid foramen – smaller opening anterior to
the jugular foramen that allows the carotid artery
to pass (supplies blood to the brain).
Carotid
foramen
Jugular
foramen
Mastoid
process
Occipital Bone
 The most posterior bone of the cranium.
 Joins the parietal bones at the lambdoid
suture.
 Has a large opening at the base called the
foramen magnum which allows the spinal
cord to connect with the brain.
Lambdoid
Suture
Occipital Bone
Foramen Magnum
Sphenoid Bone
 A butterfly-shaped bone that is seen on
the sides of the cranium, anterior to the
temporal bones
 Forms the backs of the eye orbits.
 Separates the brain from the face.
Sphenoid Bone
Sphenoid
Bone
Sphenoid Bone
Ethmoid Bone
 Irregularly shaped bone
that is anterior to the
sphenoid bone.
 Forms the roof of the
nasal cavity and part of
the medial walls of the
orbits (eye sockets).
Ethmoid Bone
The Young Cranium
 The infants face is very small compared to the
size of the cranium, but the skull as a whole is
large compared to the size of the body.
*As mentioned before, some areas of cartilage
still have to be converted to bone.
 The young cranium also has fibrous membranes,
or fontanels, where the cranial bones do not
quite meet. These are commonly referred to as
“soft spots”.
Eventually the bones grow and the
fontanels ossify.