Skull
Overview:
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The bones of the skull protect the brain
and the special sense organs (sight, smell,
hearing, equilibrium and taste)
They form the boundaries to the entrance
of the digestive and respiratory systems
They also provide attachment to the facial
muscles and the powerful muscles of
mastication
Skull
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The facial bones:
• The facial bones form the boundaries of the
nasal cavity, bony orbit, and the roof and
lateral walls of the oral cavity.
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The braincase bones:
• The bones of the braincase (neurocranium)
form the boundaries of the cranial cavity
that encloses the brain and the meninges
The facial bones
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The facial bones can be classified into two groups:
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A. Paired bones of the facial bones:
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1. Lacrimal
2. Nasal
3. Maxilla
4. Zygomatic
5. Incisive
6. Palatine
7. Pterygoid
8. Dorsal nasal concha
9. Ventral nasal concha
10. Mandible bone
Unpaired bones of the facial bones:
• 1. Vomer
• 2. Hyoid
A. Paired bones of the facial bones
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1. Lacrimal
located in the rostromedial
aspect of the orbit.
At its center there is the fossa for
the lacrimal sac, where the
osseous lacrimal canal begins.
The lacrimal bone articulates
With:
frontal bone, maxilla,
palatine bone, zygomatic bone
and ethmoid bone.
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A. Paired bones of the facial bones
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2. Nasal:
The nasal bone is very short in
brachycephalic skull.
Its internal surface is covered by
mucous membrane in live animal.
The nasal bone
articulates
with:
the frontal ,
maxilla and
incisive bone.
A. Paired bones of the facial bones
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3. Maxilla:
The maxilla is the largest bone of the
face.
Together with the incisive bone, the
maxilla forms the upper jaw.
On its external surface there is the
infraorbital foramen
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for the passage of infraorbital nerve, vein
and artery.
A. Paired bones of the facial bones
infraorbital canal:
 The canal begins at the maxillary
foramen and ends at the infraorbital
foramen.
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The short infraorbital canal lies
dorsal to the upper fourth premolar.
A. Paired bones of the facial bones
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4. Zygomatic:
The zygomatic bone forms the
zygomatic arch (rostral part)
together with the zygomatic process
of the temporal bone.
It articulates with the maxilla,
lacrimal and temporal bones.
A. Paired bones of the facial bones
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5. Incisive (Premaxilla):
The incisive bone contains three
alveoli for the upper incisor teeth.
It articulates with the maxilla, vomer
and nasal bone.
A. Paired bones of the facial bones
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6. Palatine:
The palatine bone forms the caudal
part of the hard palate.
It is divided into horizontal and
perpendicular laminae.
Each horizontal lamina has two
surfaces, palatine and nasal.
A. Paired bones of the facial bones
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6. Palatine:
palatine canal:
Running through the palatine bone is the
palatine canal, which provides passage
for the major palatine artery, vein and
nerve.
The palatine canal begins at the caudal
palatine foramen in the pterygopalatine
fossa and terminates in the hard palate
through the major and minor palatine
foramina.
A. Paired bones of the facial bones
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7. Pterygoid:
The pterygoid is small four-sided
bone that articulates with the medial
surface of the pterygoid process of
the sphenoid bone.
A. Paired bones of the facial bones
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8. Dorsal nasal concha:
The dorsal nasal concha is attached to the
ethmoidal crest on the inner wall of the
nasal bone.
The dorsal nasal concha is a simple curved
shelf of bone.
The space ventral to the dorsal nasal
concha is the middle meatus and the
space dorsal to it is the dorsal meatus.
A. Paired bones of the facial bones
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9. Ventral nasal concha:
The ventral nasal concha is attached to
the conchal crest on the medial wall of the
maxilla.
It is formed of primary and secondary
bony scrolls.
The space between the conchae and the
nasal septum is the common meatus,
whereas the space dorsal to the conchae
is the middle meatus and the space
ventral to it is the ventral meatus.
A. Paired bones of the facial bones
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10. Mandible:
The mandible consists of two parts
that are united rostrally at the
symphysis.
Each part is divided into a horizontal
body, and a vertical ramus.
The body carries the lower teeth,
and the ramus articulates with the
temporal bone.
A. Paired bones of the facial bones
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10. Mandible:
The dorsal (alveolar) border of the
mandible bears alveoli for the lower
incisors, canine, premolars and molar
teeth.
The lateral surface of the ramus
presents a triangular depression, the
masseteric fossa, for the
attachment of the masseter muscle.
B. Unpaired bones of the facial bones
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1. Vomer:
The vomer is a single bone that extends
obliquely from the base of the cranial
cavity to the upper surface of the hard
palate.
It forms the caudoventral part of the nasal
septum.
The vomer articulates with the sphenoid
bone, ethmoid bone, palatine bones,
maxilla and incisive bones.
B. Unpaired bones of the facial bones
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2. Hyoid bones:
hyoid apparatus extend from
the mastoid process of the
skull to the thyroid cartilage of
the larynx.
They support and stabilize the
tongue and the larynx.
B. Unpaired bones of the facial bones
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The hyoid apparatus consists of :
• stylohyoid
• Epihyoid
• Ceratohyoid
• basihyoid
• thyrohyoid
• The basihyoid is the only single bone that
connects the paired bones from each side at the
root of the tongue.
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Attaching to the free end of the stylohyoid is the
tympanohyoid cartilage, which articulates with the mastoid
process.
The bones of the braincase
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Neurocranium form the boundaries of
the cranial cavity that encloses the
brain and the meninges.
The roof of the cavity (calvaria) is
formed by the interparietal, parietal
and frontal bones.
The lateral boundaries of each side
are formed by the temporal bone.
The bones of the braincase
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The floor is formed by the sphenoid
bone and the basilar part of the
occipital bone.
The caudal (nuchal) wall is formed by
the occipital bone and the rostral wall
is formed by the ethmoid bone.
The bones of the braincase can
be classified into two groups:
A. Paired bones of the braincase:
• 1. Frontal
• 2. Temporal
• 3. Parietal
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B. Unpaired bones of the braincase:
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4.
Interparietal
Occipital
Sphenoid
Ethmoid
A. Paired bones of the braincase:
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1. Frontal bone:
The frontal bones lie between the
nasal bones and maxilla rostrally,
and the parietal bones caudally.
Ventrally the frontal bones articulate
with sphenoid, palatine and lacrimal
bones.
They form the rostral part of the
cranial cavity.
A. Paired bones of the braincase:
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The frontal bones participate in the
formation of the dorsomedial part of
the orbit, and envelop the ethmoid
bone.
A. Paired bones of the braincase:
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2. Temporal bones:
The temporal bones contribute to the
formation of the lower lateral wall and part
of the ventral wall of the cranial cavity
The temporal bone is a compound bone
that is composed of three parts,
squamous part, petrous part and tympanic
part.
A. Paired bones of the braincase:
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2. Temporal bones:
The squamous part carries the zygomatic process
rostrolaterally, which forms the zygomatic arch with the
zygomatic process of the temporal bone.
• The base of the zygomatic process articulates with the
condylar process of the mandible at the mandibular fossa
to form the temporomandibular joint.
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The petrous part bears the mastoid process, which
articulates with the hyoid bone.
The tympanic part possesses the large tympanic bulla.
The petrous and typanic parts enclose the middle and inner
ear.
A. Paired bones of the braincase:
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3. Parietal bone:
The parietal bones are paired and they
form the roof and part of the lateral sides
of the cranial cavity.
The parietal bones join the frontal bones
rostrally and the occipital bones caudally.
Ventrally the parietal bones meet the
squamous temporal and basisphenoid
bones
B. Unpaired bones of the braincase
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1. Interparietal:
The interparietal is small bone
wedged in between the two parietal
bones.
It fuses with the occipital bone and
bears the caudal part of the sagittal
crest.
B. Unpaired bones of the braincase
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2. Occipital:
The occipital bone is formed by paired
• exoccipitals
• supraoccipital
• basioccipital
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The dorsolateral borders form the
nuchal crest at the junction with the
parietal and the temporal bones.
B. Unpaired bones of the braincase
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2. Occipital:
The external occipital protuberance is
formed dorsally in the middle between the
nuchal crests, where the interparietal fused
with the occipital.
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The brain stem exists the cranial cavity
through the large foramen magnum.
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The hypoglossal canal passes through the
ventral part of the occipital bone.
• It provides passage for the hypoglossal nerve.
B. Unpaired bones of the braincase
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3. Sphenoid:
The sphenoid is formed of two bones,
the rostral presphenoid and the
caudal basisphenoid.
The sphenoid bones form the rostral
base of the braincase.
Passing through the sphenoid bone
are the optic canal, orbital fissure,
and alar canal in the caudal part of
the orbit.
B. Unpaired bones of the
braincase
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3. Sphenoid:
The optic canal
• passage of the optic nerve
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The orbital fissure
• passage of oculomotor, trochlear,
abducent, and ophthalmic nerves.
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The alar canal begins at the caudal
alar foramen and ends at the rostral
alar foramen.
• It provides a passage for the maxillary
artery and nerve
B. Unpaired bones of the braincase
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4. Ethmoid:
The ethmoid bone is hidden between the
cranial and facial parts of the skull.
It consists of
• a median perpendicular plate
• a cribriform plate
• the ethmoidial labyrinth.
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consists of the ectoturbinates and
endoturbinates.