210
UNIT TWO
opening near the mastoid process, the
carotid canal,
transmits the internal carotid artery. An opening between
the temporal and occipital bones, the
jugular foramen,
accommodates the internal jugular vein
(f g. 7.20)
.
The mastoid process may become infected. The tissues in this region of
the temporal bone contain a number of interconnected air cells lined
with mucous membranes that communicate with the middle ear. These
spaces sometimes become inF
amed when microorganisms spread into
them from an infected middle ear
(otitis media)
. The resulting mastoid
infection, called
mastoiditis,
is of particular concern because nearby
membranes that surround the brain may become infected.
4.
Temporal bones.
A temporal (tem
por-al) bone on each
side of the skull joins the parietal bone along a
squamous
suture.
The temporal bones form parts of the sides and the
base of the cranium. Located near the inferior margin is an
opening, the
external acoustic
(auditory)
meatus,
which
leads inward to parts of the ear. The temporal bones also
house the internal ear structures and have depressions
called the
mandibular fossae
(glenoid fossae) that articulate
with condyles of the mandible. Below each external
acoustic meatus are two projections—a rounded
mastoid
process
and a long, pointed
styloid process
(F g. 7.19).
The mastoid process provides an attachment for certain
muscles of the neck, whereas the styloid process anchors
muscles associated with the tongue and pharynx. An
Coronal suture
Frontal bone
Sphenoid bone
Ethmoid bone
Lacrimal bone
Nasal bone
Zygomatic bone
Maxilla
Mental foramen
Mandible
Coronoid process
Styloid process
Mandibular condyle
Mastoid process
External acoustic meatus
Temporal process
of zygomatic bone
Zygomatic process
of temporal bone
Occipital bone
Temporal bone
Parietal bone
Lambdoid suture
Squamous suture
FIGURE 7.19
Right lateral view of the skull.
TABLE
7.5
|
Cranial Bones
Name and Number
Description
Special Features
±rontal (1)
±orms forehead, roof of nasal cavity, and roofs of orbits
Supraorbital foramen, frontal sinuses
Parietal (2)
±orm side walls and roof of cranium
±used at midline along sagittal suture
Occipital (1)
±orms back of skull and base of cranium
±oramen magnum, occipital condyles
Temporal (2)
±orm side walls and F
oor of cranium
External acoustic meatus, mandibular fossa, mastoid process, styloid process,
zygomatic process
Sphenoid (1)
±orms parts of base of cranium, sides of skull, and
F
oors and sides of orbits
Sella turcica, sphenoidal sinuses
Ethmoid (1)
±orms parts of roof and walls of nasal cavity, F
oor of
cranium, and walls of orbits
Cribriform plates, perpendicular plate, superior and middle nasal conchae,
ethmoidal sinuses, crista galli
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