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Occipital bone
• The occipital bone is situated at the posterior
and inferior part of the cranium, is trapezoid
in shape and concave forwards.
• Foramen Magnum: the largest opening in the
skull, through it passes the spinal cord.
• Squama: The curved, expanded plate behind
the foramen magnum.
• Basilar part: the thick, somewhat
quadrilateral piece in front of the foramen
magnum.
• Lateral portion: on either side of the foramen
magnum, containing the condyles for
articulation with the superior facets of the
atlas.
• External surface: is convex and presents
midway between the top of the bone and the
foramen magnum a prominence, the external
occipital protuberance.
• Highest nuchal line: the higher line, extending
laterally from the external occipital
protuberance on either side.
• Superior nuchal line: the lower line from
these two.
• Median nuchal line: is a ridge or crest,
extending from the external occipital
protuberance to the foramen magnum.
• Inferior nuchal line: running from the middle
of the middle nuchal line across either half of
the nuchal plane.
• The occipital bone articulates with 6 bones:
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the two parietals,
the two temporals,
the sphenoid,
the atlas.
Temporal bone
• The temporal bones are situated at the sides
and base of the skull.
• Each consists of five parts:
The squama
The petrous
The mastoid portion
The tympanic
The Styloid process.
• The Squama: The squama is thin and forms
the anterior and upper part of the bone.
• Projecting form the squama is the zygomatic
process that articulates with the temporal
process of the zygomatic bone.
• squamous portion of the temporal bone is the
most sensitive site to skull fracture
• Mandibular fossa: oval depression, for the
reception of the condyle of the mandible, that
will form the tempromandibular joint (TMJ)
• The superior border articulates with the
parietal bone forming the squamous suture.
• The anteroinferior border articulates with the
greater wing of the sphenoid bone.
• The mastoid portion contains the mastoid
process and the mastoid air cells.
• Petrous portion: The petrous portion
or pyramid is pyramidal and is wedged in at
the base of the skull between the sphenoid
and occipital bones, and contains, in its
interior, the essential parts of the organ of
hearing.
• petrous portion is the thickest portion of the
cranial bones.
• Articulations:
• The temporal articulates with 5 bones:
occipital,
parietal,
sphenoid,
mandible
zygomatic bone.
Sphenoid bone
• The sphenoid bone is situated at the
base of the skull in front of the temporals
and basilar part of the occipital.
• Body: The body, more or less cubical in
shape, is hollowed out in its interior to form
two large cavities, the sphenoidal air
sinuses, which are separated from each
other by a septum.
• Sella turcica: a deep depression,
containing the pituitary gland.
• Dorsum sellæ: posterior part of the sella
turcica.
• Clivus is located posteriory to the dorsum
selles
• Laterally, 2 wings, the smaller one is
called the lesser wing and the larger one
is called greater wing
• The lesser wing ends medially with Ant
clinoid process
• Pterygoid Processes: one on either side,
descend perpendicularly from the regions
where the body and great wings unite.
3 pairs of openings:
• Foramen rotundum
• Foramen ovale
• Foramen spinosum
• Between the body and the lesser wing is
canal (chiasmatic groove) through which
the optic nerve passes to the orbital cavity
ends at the optic foramen
Ant
clinoid
Lesser
wing
Greater
wing
Sella
turcica
Dorsum
sella
Articulations
• The sphenoid
articulates
with twelve bones:
four single, the
• vomer,
• ethmoid,
• frontal,
• and occipital
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and four paired:
the parietal,
temporal,
zygomatic,
and palatine
Ethmoid bone
• The ethmoid bone is exceedingly light
and spongy, and cubical in shape; it is
situated at the anterior part of the base of
the cranium, between the two orbits, at the
roof of the nose.
• consists of four parts:
horizontal or cribriform plate: forming
part of the base of the cranium, superior to
the cribriform plate a small part is called
crista galli
• perpendicular plate, constituting part of
the nasal septum;
• two lateral masses: contains the
ethmoidal sinuses
Articulation
• The ethmoid articulates with:
• the cranium—the frontal, the sphenoid,
• and of the face—the two nasals, two
maxillæ, two lacrimals, two palatines, two
inferior nasal conchæ, and the vomer.