Lecture Lecture

SkullSkull

Overview:Overview:

The bones of the skull protect the brain The bones of the skull protect the brain and the special sense organs (sight, smell, and the special sense organs (sight, smell, hearing, equilibrium and taste)hearing, equilibrium and taste)

They form the boundaries to the entrance They form the boundaries to the entrance of the digestive and respiratory systemsof the digestive and respiratory systems

They also provide attachment to the facial They also provide attachment to the facial muscles and the powerful muscles of muscles and the powerful muscles of masticationmastication

SkullSkull The facial bones:The facial bones:

• The facial bones form the boundaries of the The facial bones form the boundaries of the nasal cavity, bony orbit, and the roof and nasal cavity, bony orbit, and the roof and lateral walls of the oral cavity.lateral walls of the oral cavity.

The braincaseThe braincase bones: bones:

• The bones of the braincase (neurocranium) The bones of the braincase (neurocranium) form the boundaries of the cranial cavity form the boundaries of the cranial cavity that encloses the brain and the meninges that encloses the brain and the meninges

The facial bonesThe facial bones The facial bones can be classified into two groups: The facial bones can be classified into two groups:

A. Paired bones of the facial bones:A. Paired bones of the facial bones:• 1. Lacrimal1. Lacrimal• 2. Nasal 2. Nasal • 3. Maxilla3. Maxilla• 4. Zygomatic4. Zygomatic• 5. Incisive5. Incisive• 6. Palatine6. Palatine• 7. Pterygoid7. Pterygoid• 8. Dorsal nasal concha8. Dorsal nasal concha• 9. Ventral nasal concha9. Ventral nasal concha• 10. Mandible bone 10. Mandible bone

Unpaired bones of the facial bones:Unpaired bones of the facial bones:• 1. Vomer1. Vomer• 2. Hyoid2. Hyoid

A. Paired bones of the facial bonesA. Paired bones of the facial bones

1. Lacrimal1. Lacrimal located in the rostromedial located in the rostromedial

aspect of the orbit. aspect of the orbit. At its center there is the fossa At its center there is the fossa

for the lacrimal sac, where the for the lacrimal sac, where the osseous lacrimal canal begins.osseous lacrimal canal begins.

The lacrimal bone articulates The lacrimal bone articulates With:With:frontal bone, maxilla, frontal bone, maxilla, palatine bone, zygomatic bone palatine bone, zygomatic bone and ethmoid bone.and ethmoid bone.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

2. Nasal:2. Nasal:

The nasal bone is very short in The nasal bone is very short in brachycephalic skull. brachycephalic skull.

Its internal surface is covered by Its internal surface is covered by mucous membrane in live animal. mucous membrane in live animal.

The nasal bone The nasal bone articulates articulates with:with: the frontal , the frontal , maxilla and maxilla and incisive bone.incisive bone.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

3. Maxilla:3. Maxilla: The maxilla is the largest bone of the The maxilla is the largest bone of the

face. face. Together with the incisive bone, the Together with the incisive bone, the

maxilla forms the upper jaw.maxilla forms the upper jaw. On its external surface there is the On its external surface there is the

infraorbital forameninfraorbital foramen for the passage of infraorbital nerve, vein for the passage of infraorbital nerve, vein

and artery. and artery.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

infraorbital canal:infraorbital canal: The canal begins at the The canal begins at the maxillary maxillary

foramenforamen and ends at the infraorbital and ends at the infraorbital foramen. foramen.

The short The short infraorbital canalinfraorbital canal lies lies dorsal to the upper fourth premolar.dorsal to the upper fourth premolar.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

4. Zygomatic:4. Zygomatic: The zygomatic bone forms the The zygomatic bone forms the

zygomatic arch (rostral part) zygomatic arch (rostral part) together with the zygomatic process together with the zygomatic process of the temporal bone. of the temporal bone.

It articulates with the maxilla, It articulates with the maxilla, lacrimal and temporal bones.lacrimal and temporal bones.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

5. Incisive (Premaxilla):5. Incisive (Premaxilla):

The incisive bone contains three The incisive bone contains three alveoli for the upper incisor teeth. alveoli for the upper incisor teeth.

It articulates with the maxilla, vomer It articulates with the maxilla, vomer and nasal bone.and nasal bone.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

6. Palatine:6. Palatine: The palatine bone forms the caudal The palatine bone forms the caudal

part of the hard palate. part of the hard palate. It is divided into horizontal and It is divided into horizontal and

perpendicular laminae. perpendicular laminae. Each horizontal lamina has two Each horizontal lamina has two

surfaces, palatine and nasal.surfaces, palatine and nasal.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

6. Palatine:6. Palatine:palatine canal:palatine canal:

Running through the palatine bone is the Running through the palatine bone is the palatine canalpalatine canal, which provides passage , which provides passage for the major palatine artery, vein and for the major palatine artery, vein and nerve. nerve.

The palatine canal begins at the The palatine canal begins at the caudal caudal palatine foramenpalatine foramen in the pterygopalatine in the pterygopalatine fossa and terminates in the hard palate fossa and terminates in the hard palate through the through the majormajor and and minor palatine minor palatine foraminaforamina..

A. Paired bones of the facial bonesA. Paired bones of the facial bones

7. Pterygoid:7. Pterygoid:

The pterygoid is small four-sided The pterygoid is small four-sided bone that articulates with the medial bone that articulates with the medial surface of the pterygoid process of surface of the pterygoid process of the sphenoid bone.the sphenoid bone.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

8. Dorsal nasal concha:8. Dorsal nasal concha: The dorsal nasal concha is attached to the The dorsal nasal concha is attached to the

ethmoidal crestethmoidal crest on the inner wall of the on the inner wall of the nasal bone. nasal bone.

The dorsal nasal concha is a simple curved The dorsal nasal concha is a simple curved shelf of bone. shelf of bone.

The space ventral to the dorsal nasal The space ventral to the dorsal nasal concha is the concha is the middle meatusmiddle meatus and the and the space dorsal to it is the space dorsal to it is the dorsal meatusdorsal meatus..

A. Paired bones of the facial bonesA. Paired bones of the facial bones

9. Ventral nasal concha:9. Ventral nasal concha: The ventral nasal concha is attached to The ventral nasal concha is attached to

the conchal crest on the medial wall of the the conchal crest on the medial wall of the maxilla. maxilla.

It is formed of primary and secondary It is formed of primary and secondary bony scrolls. bony scrolls.

The space between the conchae and the The space between the conchae and the nasal septum is the nasal septum is the common meatuscommon meatus, , whereas the space dorsal to the conchae whereas the space dorsal to the conchae is the is the middle meatusmiddle meatus and the space and the space ventral to it is the ventral to it is the ventral meatusventral meatus..

A. Paired bones of the facial bonesA. Paired bones of the facial bones

10. Mandible:10. Mandible: The mandible consists of two parts The mandible consists of two parts

that are united rostrally at thethat are united rostrally at the symphysissymphysis. .

Each part is divided into a horizontal Each part is divided into a horizontal bodybody, and a vertical , and a vertical ramusramus. .

The body carries the lower teeth, and The body carries the lower teeth, and the ramus articulates with the the ramus articulates with the temporal bone. temporal bone.

A. Paired bones of the facial bonesA. Paired bones of the facial bones

10. Mandible:10. Mandible: The dorsal (alveolar) border of the The dorsal (alveolar) border of the

mandible bears alveoli for the lower mandible bears alveoli for the lower incisors, canine, premolars and molar incisors, canine, premolars and molar teeth. teeth.

The lateral surface of the ramus The lateral surface of the ramus presents a triangular depression, the presents a triangular depression, the masseteric fossamasseteric fossa, for the , for the attachment of the masseter muscle. attachment of the masseter muscle.

B. Unpaired bones of the facial bonesB. Unpaired bones of the facial bones

1. Vomer:1. Vomer: The vomer is a single bone that extends The vomer is a single bone that extends

obliquely from the base of the cranial obliquely from the base of the cranial cavity to the upper surface of the hard cavity to the upper surface of the hard palate. palate.

It forms the caudoventral part of the nasal It forms the caudoventral part of the nasal septum. septum.

The vomer articulates with the sphenoid The vomer articulates with the sphenoid bone, ethmoid bone, palatine bones, bone, ethmoid bone, palatine bones, maxilla and incisive bones.maxilla and incisive bones.

B. Unpaired bones of the facial bonesB. Unpaired bones of the facial bones

2. Hyoid bones:2. Hyoid bones:

hyoid apparatus extend from hyoid apparatus extend from the mastoid process of the the mastoid process of the skull to the thyroid cartilage of skull to the thyroid cartilage of the larynx. the larynx.

They support and stabilize the They support and stabilize the tongue and the larynx.tongue and the larynx.

B. Unpaired bones of the facial bonesB. Unpaired bones of the facial bones

The hyoid apparatus consists of :The hyoid apparatus consists of :

• stylohyoidstylohyoid• EpihyoidEpihyoid• CeratohyoidCeratohyoid• basihyoidbasihyoid • thyrohyoidthyrohyoid

• The The basihyoidbasihyoid is the only single bone that connects is the only single bone that connects the paired bones from each side at the root of the the paired bones from each side at the root of the tongue.tongue.

Attaching to the free end of the stylohyoid is the tympanohyoid Attaching to the free end of the stylohyoid is the tympanohyoid cartilage, which articulates with the mastoid process. cartilage, which articulates with the mastoid process.

The bones of the braincaseThe bones of the braincase

Neurocranium form the boundaries of Neurocranium form the boundaries of the cranial cavity that encloses the the cranial cavity that encloses the brain and the meninges. brain and the meninges.

The roof of the cavity (calvaria) is The roof of the cavity (calvaria) is formed by the interparietal, parietal formed by the interparietal, parietal and frontal bones. and frontal bones.

The lateral boundaries of each side The lateral boundaries of each side are formed by the temporal bone. are formed by the temporal bone.

The bones of the braincaseThe bones of the braincase

The floor is formed by the sphenoid The floor is formed by the sphenoid bone and the basilar part of the bone and the basilar part of the occipital bone. occipital bone.

The caudal (nuchal) wall is formed by The caudal (nuchal) wall is formed by the occipital bone and the rostral wall the occipital bone and the rostral wall is formed by the ethmoid bone. is formed by the ethmoid bone.

The bones of the braincase can The bones of the braincase can be classified into two groups:be classified into two groups:

A. Paired bones of the braincase:A. Paired bones of the braincase: • 1. Frontal1. Frontal• 2. Temporal2. Temporal• 3. Parietal3. Parietal   

B. Unpaired bones of the braincase:B. Unpaired bones of the braincase: • 1. Interparietal1. Interparietal• 2. Occipital2. Occipital• 3. Sphenoid3. Sphenoid• 4. Ethmoid4. Ethmoid

A. Paired bones of the braincase:A. Paired bones of the braincase:

1. Frontal bone:1. Frontal bone: The frontal bones lie between the The frontal bones lie between the

nasal bones and maxilla rostrally, nasal bones and maxilla rostrally, and the parietal bones caudally. and the parietal bones caudally.

Ventrally the frontal bones articulate Ventrally the frontal bones articulate with sphenoid, palatine and lacrimal with sphenoid, palatine and lacrimal bones.bones.

They form the rostral part of the They form the rostral part of the cranial cavity. cranial cavity.

A. Paired bones of the braincase:A. Paired bones of the braincase:

The frontal bones participate in the The frontal bones participate in the formation of the dorsomedial part of formation of the dorsomedial part of the orbit, and envelop the ethmoid the orbit, and envelop the ethmoid bone. bone.

A. Paired bones of the braincase:A. Paired bones of the braincase:

2. Temporal bones: 2. Temporal bones:

The temporal bones contribute to the The temporal bones contribute to the formation of the lower lateral wall and part formation of the lower lateral wall and part of the ventral wall of the cranial cavity of the ventral wall of the cranial cavity

The temporal bone is a compound bone The temporal bone is a compound bone that is composed of three parts, squamous that is composed of three parts, squamous part, petrous part and tympanic part. part, petrous part and tympanic part.

A. Paired bones of the braincase:A. Paired bones of the braincase:

2. Temporal bones: 2. Temporal bones:

The The squamous partsquamous part carries the carries the zygomatic processzygomatic process rostrolaterally, which forms the rostrolaterally, which forms the zygomatic archzygomatic arch with the with the zygomatic zygomatic processprocess of the of the temporaltemporal bone. bone.

• The base of the zygomatic process articulates with the The base of the zygomatic process articulates with the condylar processcondylar process of the mandible at the of the mandible at the mandibular fossamandibular fossa to form the to form the temporomandibular jointtemporomandibular joint. .

The The petrous partpetrous part bears the bears the mastoid processmastoid process, which , which articulates with the hyoid bone. articulates with the hyoid bone.

The The tympanic parttympanic part possesses the large possesses the large tympanic bullatympanic bulla. . The petrous and typanic parts enclose the middle and inner The petrous and typanic parts enclose the middle and inner ear. ear.

A. Paired bones of the braincase:A. Paired bones of the braincase:

3. Parietal bone: 3. Parietal bone: The parietal bones are paired and they The parietal bones are paired and they

form the roof and part of the lateral sides form the roof and part of the lateral sides of the cranial cavity.of the cranial cavity.

The parietal bones join the frontal bones The parietal bones join the frontal bones rostrally and the occipital bones caudally. rostrally and the occipital bones caudally.

Ventrally the parietal bones meet the Ventrally the parietal bones meet the squamous temporal and basisphenoid squamous temporal and basisphenoid bonesbones

B. Unpaired bones of the braincaseB. Unpaired bones of the braincase

1. Interparietal:1. Interparietal: The interparietal is small bone The interparietal is small bone

wedged in between the two parietal wedged in between the two parietal bones. bones.

It fuses with the occipital bone and It fuses with the occipital bone and bears the caudal part of the bears the caudal part of the sagittal sagittal crestcrest..

B. Unpaired bones of the braincaseB. Unpaired bones of the braincase

2. Occipital:2. Occipital: The occipital bone is formed by The occipital bone is formed by

paired paired • exoccipitalsexoccipitals• supraoccipital supraoccipital • basioccipitalbasioccipital

The dorsolateral borders form the The dorsolateral borders form the nuchal crest at the junction with the nuchal crest at the junction with the parietal and the temporal bones.parietal and the temporal bones.

B. Unpaired bones of the braincaseB. Unpaired bones of the braincase

2. Occipital:2. Occipital:

The external occipital protuberance is The external occipital protuberance is formed dorsally in the middle between the formed dorsally in the middle between the nuchal crests, where the interparietal fused nuchal crests, where the interparietal fused with the occipital. with the occipital.

The brain stem exists the cranial cavity The brain stem exists the cranial cavity through the large foramen magnum.through the large foramen magnum.

The hypoglossal canal passes through the The hypoglossal canal passes through the ventral part of the occipital bone.ventral part of the occipital bone.• It provides passage for the hypoglossal nerve.It provides passage for the hypoglossal nerve.

B. Unpaired bones of the braincaseB. Unpaired bones of the braincase

3. Sphenoid:3. Sphenoid: The sphenoid is formed of two bones, The sphenoid is formed of two bones,

the rostral presphenoid and the the rostral presphenoid and the caudal basisphenoid. caudal basisphenoid.

The sphenoid bones form the rostral The sphenoid bones form the rostral base of the braincase. base of the braincase.

Passing through the sphenoid bone Passing through the sphenoid bone are the optic canal, orbital fissure, are the optic canal, orbital fissure, and alar canal in the caudal part of and alar canal in the caudal part of the orbit.the orbit.

B. Unpaired bones of the B. Unpaired bones of the braincasebraincase

3. Sphenoid:3. Sphenoid: The optic canal The optic canal

• passage of the optic nerve passage of the optic nerve The orbital fissure The orbital fissure

• passage of oculomotor, trochlear, passage of oculomotor, trochlear, abducent, and ophthalmic nerves.abducent, and ophthalmic nerves.

The alar canal begins at the caudal The alar canal begins at the caudal alar foramen and ends at the rostral alar foramen and ends at the rostral alar foramen. alar foramen. • It provides a passage for the maxillary It provides a passage for the maxillary

artery and nerveartery and nerve

B. Unpaired bones of the braincaseB. Unpaired bones of the braincase

4. Ethmoid:4. Ethmoid:

The ethmoid bone is hidden between the The ethmoid bone is hidden between the cranial and facial parts of the skull. cranial and facial parts of the skull.

It consists of It consists of • a a medianmedian perpendicular plateperpendicular plate• a a cribriform platecribriform plate • the the ethmoidial labyrinthethmoidial labyrinth..

consists of the consists of the ectoturbinatesectoturbinates and and eendoturbinatesndoturbinates..