Download Temporal bone

PARTS OF THE SKULL
Part 1: Bones of the Cranium
OBJECTIVES
• Be able to locate and identify the
bones and the major features of the
bones that comprise the skull
• Be able to describe the distinguishing
features between males and females
in the features of the skull
ANTERIOR VIEW OF THE SKULL
ORBIT OF THE EYE
LATERAL VIEW OF THE SKULL
INFERIOR VIEW OF THE SKULL
THE HUMAN SKULL
• Consists of 22 bones that are firmly
interlocked along sutures, except for the
lower jaw
• Eight of these bones make up the cranium
• Fourteen of these bones make up the
facial skeleton
• The mandible or lower jawbone is movable
and attached to the cranium by ligaments
• Some facial and cranial bones together
form the orbit of the eye
THE CRANIUM
• Encloses and protects the brain
• Its surface provides attachments for
muscles that allow chewing and
head movements
• Some cranial bones contain air-filled
cavities called paranasal sinuses
THE SINUSES
• These cavities are lined with mucous
membranes and are connected by
passageways to the nasal cavity
• They reduce the weight of the skull
• Serve as resonant sound chambers by
increasing the intensity of the voice
PARANASAL SINUSES
BONES OF THE CRANIUM
• Frontal bone
• Parietal bone (2)
• Occipital bone
• Temporal bone (2)
• Sphenoid bone
• Ethmoid bone
FRONTAL BONE
• Forms the anterior portion of the skull above
the eyes
• Makes up the forehead, the roof of the nasal
cavity and the roofs of the orbits (sockets) of
the eyes
• On the upper margin of each orbit, the frontal
bone is marked by a supraorbital foramen (or
supraorbital notch)
• Through here blood vessels and nerve pass to
the tissues of the forehead
• Within the frontal bone, are the two frontal
sinuses
• The frontal bone is a single bone in adults but
develops in two parts and is not completely
fused until 5-6 years of age
PARIETAL BONE
• Locate on each side of the skull just behind
the frontal bone
• Shaped like a curve plate and has four
borders
• Together, the parietal bones form the
bulging sides and roof of the cranium
• They are fused at the midline along the
coronal suture
OCCIPITAL BONE
• Joins the parietal bones along the
lambdoid suture
• Forms the back of the skull and the base of
the cranium
• A large opening on its lower surface is the
foramen magnum
• This is where the inferior part of the brain
stem connects with the spinal cord
• Rounded processes called occipital
condyles, located on each side of the
foramen magnum, articulate with the first
vertebra (atlas) of the vertebral column
TEMPORAL BONE
• Located on each side of the skull
• It joins the parietal bone along a squamous
suture
• Forms part of the side and base of the cranium
• Located near the inferior margin is an opening,
the external acoustic meatus, which leads
inward to parts of the ear
• The temporal bones house the internal ear
structures
• They also have depressions called the
mandibular fossae (glenoid fossae) that
articulate with condyles of the mandible
PROJECTIONS OF THE
TEMPORAL BONE
• Below each external acoustic meatus are two
projections:
• A rounded mastoid process and a long,
pointed styloid process
• The mastoid process provides an attachment
for certain muscles of the neck
• The styloid process anchors muscles
associated with the tongue and pharynx
• The zygomatic process projects anteriorly from
the temporal bone
• It joins the temporal process of the zygomatic
bone and helps form the prominence of the
cheek known as the zygomatic arch
OPENINGS NEAR THE
TEMPORAL BONE
• The carotid canal, which transmits the
internal carotid artery is located near the
mastoid process
• Between the temporal and occipital bones
is an opening called the jugular foramen,
which accommodates the internal jugular
vein
SPHENOID BONE
• Is wedged between several other bones in
the anterior portion of the cranium
• Consists of a central part and two wing-like
structures that extend laterally toward each
side of the skull
• Helps to form the base of the cranium, the
sides of the skull, and the floors and sides of
the orbits
• A portion of the sphenoid bone indents to
form the saddle-shaped sella turcica (Turk’s
saddle)
• The pituitary gland lies here
• There are also two sphenoidal sinuses within
ETHMOID BONE
• Is located in front of the sphenoid bone
• Consists of two masses, one on each side of
the nasal cavity that are joined horizontally by
thin cribriform plates
• These plates form part of the roof of the nasal
cavity and nerves associated with the sense of
smell pass through tiny openings called
olfactory foramina
• Portions of this bone also form sections of the
cranial floor, orbital walls, and nasal cavity
walls
• It contains ethmoidal sinuses, who warm and
filter the air that enters the respiratory system
OTHER STRUCTURES CONNECTED TO
THE ETHMOID BONE
• A perpendicular plate projects downward in
the midline from the cribriform plates to form
most of the nasal septum
• Delicate, scroll-shaped plates called the
superior nasal concha and the middle nasal
concha project inward toward the
perpendicular plate
• Projecting upward into the cranial cavity
between the cribriform plates is a triangular
process called the crista galli (cock’s comb)
THE ETHMOID BONE