1. Lecture
Skull

2. Overview:
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

3. Skull The facial bones: The braincase bones:
The facial bones form the boundaries of the nasal cavity, bony orbit, and the roof and lateral walls of the oral cavity.
The braincase bones:
The bones of the braincase (neurocranium) form the boundaries of the cranial cavity that encloses the brain and the meninges

4. The facial bones The facial bones can be classified into two groups:
A. Paired bones of the facial bones:
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

7. A. Paired bones of the facial bones
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.

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

9. A. Paired bones of the facial bones
2. Nasal:
The nasal bone is very short in brachycephalic skull.
Its internal surface is covered by mucous membrane in live animal.

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

11. A. Paired bones of the facial bones
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
for the passage of infraorbital nerve, vein and artery.

12. A. Paired bones of the facial bones
infraorbital canal:
The canal begins at the maxillary foramen and ends at the infraorbital foramen.
The short infraorbital canal lies dorsal to the upper fourth premolar.

17. A. Paired bones of the facial bones
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.

19. A. Paired bones of the facial bones
5. Incisive (Premaxilla):
The incisive bone contains three alveoli for the upper incisor teeth.
It articulates with the maxilla, vomer and nasal bone.

23. A. Paired bones of the facial bones
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.

24. A. Paired bones of the facial bones
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.

28. A. Paired bones of the facial bones
7. Pterygoid:
The pterygoid is small four-sided bone that articulates with the medial surface of the pterygoid process of the sphenoid bone.

30. A. Paired bones of the facial bones
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.

33. A. Paired bones of the facial bones
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.

37. A. Paired bones of the facial bones
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.

38. A. Paired bones of the facial bones
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.

41. B. Unpaired bones of the facial bones
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.

43. B. Unpaired bones of the facial bones
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.

44. B. Unpaired bones of the facial bones
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.
Attaching to the free end of the stylohyoid is the tympanohyoid cartilage, which articulates with the mastoid process.

47. The bones of the braincase
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.

48. The bones of the braincase
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.

49. The bones of the braincase can be classified into two groups:
A. Paired bones of the braincase:
1. Frontal
2. Temporal
3. Parietal  
B. Unpaired bones of the braincase:
1. Interparietal
2. Occipital
3. Sphenoid
4. Ethmoid

52. A. Paired bones of the braincase:
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.

53. A. Paired bones of the braincase:
The frontal bones participate in the formation of the dorsomedial part of the orbit, and envelop the ethmoid bone.

55. A. Paired bones of the braincase:
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.

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

59. A. Paired bones of the braincase:
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

62. B. Unpaired bones of the braincase
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.

65. B. Unpaired bones of the braincase
2. Occipital:
The occipital bone is formed by paired
exoccipitals
supraoccipital
basioccipital
The dorsolateral borders form the nuchal crest at the junction with the parietal and the temporal bones.

66. B. Unpaired bones of the braincase
2. Occipital:
The external occipital protuberance is formed dorsally in the middle between the nuchal crests, where the interparietal fused with the occipital.
The brain stem exists the cranial cavity through the large foramen magnum.
The hypoglossal canal passes through the ventral part of the occipital bone.
It provides passage for the hypoglossal nerve.

71. B. Unpaired bones of the braincase
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.

72. B. Unpaired bones of the braincase
3. Sphenoid:
The optic canal
passage of the optic nerve
The orbital fissure
passage of oculomotor, trochlear, abducent, and ophthalmic nerves.
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

76. B. Unpaired bones of the braincase
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.
consists of the ectoturbinates and endoturbinates.