Bones of the Skull

1. INTRODUCTION OF THE
HEAD AND NECK
• Bonesof theSkull
• Cranialbones
• Facialbones
• Base andForamenof theskull

2. A. THE HEAD
• Cranium (Skull) - skeletal
structure of the head
• supports the face and protects
the brain
• Subdivided:
• 1. Brain case or cranial vault/
bones- surrounds and
protects the brain and houses
the middle and inner ear
structures.
• 2. Facial bones - underlie the
facial structures, form the
nasal cavity, enclose the
eyeballs, and support the
teeth of the upper and lower
jaws.

3. BONESOF THE SKULL
• I. 8 CRANIAL BONES • II. FACIAL BONES

4. Cranial bones
• Cranial Cavity – interior space
that is almost completely
occupied by the brain
• Boundaries:
• Superiorly, Lateral and
Posterior: Calvaria (skullcap)
• Floor/ Base:
• Anterior Cranial Fossa
• Middle Cranial Fossa
• Posterior Cranial Fossa

5. • 2 Parietal Bone – upper
lateral side of the skull
• Parietal foramen -
inconstant foramina
• transmit the emissary
veins, draining to the
superior sagittal
sinus, and
occasionally a branch
of the occipital artery
Cranial Bones

6. • 2 Temporal bone – lower lateral side
• Squamous
• AKA squama temporalis, flattened largest part of
the temporal bone, forming part of the temporal
fossa.
• Zygomatic Process - lower part of the squama
temporalis, forms the posterior portion of the
zygomatic arch.
• Mandibular fossa – articulates the head of the
mandible. it allows the mouth to be closed and
opened, meaning it exists to perform mastication.
• Articular tubercle - contribute to the
temporomandibular joint
Cranial Bones

7. • Tympanic:
• External acoustic meatus/ external
acoustic meatus - leads from the
outside of the head to the tympanic
membrane, or eardrum membrane
• Styloid process - attachment point for
muscles and ligaments, such as the
stylomandibular ligament of the TMJ.
• Petromastoid
• Mastoid process – attachment of
muscles
• Petrous part is pyramidal shaped and
lies at the base of temporal bone. It
contains the inner ear.
• Mastoid air cells - hollowed out areas,
equalizing the pressure within the
middle ear in the case of auditory
tube dysfunction
Cranial Bones

8. • 1 Frontal bone- forehead bone
• Supraorbital foramen - opening that
provides passage for a sensory nerve to
the forehead
• Superciliary arches
• Medially: frontal bone to frontal
processes of the maxillae
• Laterally: frontal bone to zygomatic
bone
• Orbital margins
• Superiorly: frontal bone
• Laterally: zygomatic bone
• Inferiorly: maxilla
• Medially: frontal process of the
maxilla and frontal bone
Cranial Bones

9. • 1 Occipital bone - forms the
posterior skull and posterior base
of the cranial cavity
• Supreme nuchal line
• Superior nuchal line
• External occipital protuberance -
serves as an attachment site for a
ligament
• Inferior nuchal line
• External occipital crest
• Occipital condyle - articulate with the
superior aspect of the lateral mass of
the first cervical vertebra,(atlas).
Cranial Bones

10. • 1 Occipital bone
• Fossa for cerebrum
• Internal occipital
protuberance
• Fossa for cerebellum
• Jugular process-
extends laterally from
the posterior half of
the condyle and
articulates with the
jugular surface of the
temporal bone.
Cranial Bones

11. • 1 Sphenoid bone- AKA “wasp bone,”
• located in the middle and toward the front
of the skull, just in front of the occipital
bone
• Body – center cubical shaped
• Greater wing – acts as floor of the middle
cranial fossa, lateral wall of the skull,
posterolateral wall of the orbit
• Lesser Wing - separates the anterior
cranial fossa from the middle cranial fossa.
• Medial pterygoid plate- supports post
opening of the nasal cavity
• Lateral pterygoid plate- origin of
pterygoid muscles
Cranial Bones

12. • 1 Ethmoid bone
• Separates the nasal
cavity from the brain. it
is located at the roof of
the nose, between the
two orbits
Cranial Bones

13. • Crista Galli (rooster’s comb/
crest) - small upward bony
projection located at the
midline, functions as an anterior
attachment point for one of the
covering layers of the brain.
• Cribriform plate - small,
flattened area with numerous
small openings (olfactory
foramina).
• Superior and Middle nasal
concha - shelves of bone that
project into the nasal cavity
• Perpendicular plate - forms the
upper portion of the nasal
septum.
Cranial Bones

14. Joints of the Cranial bones
 Sutures- Immobile Joints
• united bones that composed the skull
 Sutural ligaments - dense, fibrous
connective tissue between the bones
A. Frontal Suture/ Coronal Suture- parietal and
frontal
B. Squamosal Suture- parietal and temporal
C. Lambdoidal Suture- parietal and occipital
D. Sagittal Suture- parietal and parietal
NOTE: TEMPOROMANDIBULAR JOINT- UNITES
THE SKULL AND MANDIBLE

15. • Forms the upper and lower
jaws, the nose, nasal cavity
and nasal septum, and the
orbit.
• Paired bones are the maxilla,
palatine, zygomatic, nasal,
lacrimal, and inferior nasal
conchae bones.
• Unpaired bones are the vomer
and mandible bones.
Facial bones

16. • 2 Maxillary Bone/ Maxilla – one of a
pair that together form the upper jaw,
much of the hard palate, the medial
floor of the orbit, and the lateral base
of the nose
• Alveolar process of the maxilla-
curved, inferior margin of the
maxillary bone that forms the upper
jaw and contains the upper teeth
• Alveolus - deep socket each tooth is
anchored
• Infraorbital foramen - exit for a
sensory nerve that supplies the nose,
upper lip, and anterior cheek.
Facial bones

17. • Palatine process - from each maxillary
bone can be seen joining together at
the midline to form the anterior
three-quarters of the hard palate
• Hard palate - bony plate that forms
the roof of the mouth and floor of the
nasal cavity, separating the oral and
nasal cavities.
• Incisive foramen – AKA anterior
palatine foramen, or nasopalatine
foramen
• funnel-shaped opening in the
bone of the oral hard palate
immediately behind the incisor
teeth
Facial bones

18. • 2 Palatine bone - irregularly
shaped bones that contribute
small areas to the lateral walls of
the nasal cavity and the medial
wall of each orbit.
• Horizontal plate – largest region
• Pyramidal process -
Facial bones

19. • 2 Zygomatic bone (cheekbone).
• forms much of the lateral wall of
the orbit and the lateral-inferior
margins of the anterior orbital
opening.
• Temporal process - projects
posteriorly, where it forms the
anterior portion of the zygomatic
arch
• Zygomaticofacial foramen -
transmits zygomatic nerve and
vessels to temporal fossa and
cheek
Facial bones

20. Facial bones
• 2 Nasal bone - forms the bony
base (bridge) of the nose
• support the cartilages that form
the lateral walls of the nose
• 2 Lacrimal bone - small,
rectangular bone that forms the
anterior, medial wall of the orbit
• Lacrimal fossa anterior portion of
the lacrimal bone forms a shallow
depression
• Nasolacrimal canal – extends
inferiorly from the lacrimal fossa

21. • 2 Inferior nasal
conchae - form a
curved bony plate
that projects into the
nasal cavity space
from the lower lateral
wall
• 1 Vomer - triangular-
shaped and forms the
posterior-inferior part
of the nasal septum
Facial bones

22. • 1 Mandible - forms the lower
jaw and is the only moveable
bone of the skull.
• Ramus of the mandible -
consists of a horizontal body and
posteriorly, a vertically oriented
• Angle of the mandible - side
margin of the mandible, where
the body and ramus come
together
Facial bones

23. • Parts of the Ramus of Mandible
• Coronoid process - flattened anterior
projection provides attachment for
one of the biting muscles.
• Condylar process - posterior
projection topped by the oval-shaped
condyle
• Mandibular condyle - articulates with
the mandibular fossa and articular
tubercle of the temporal bone
• Mandibular notch - broad U-shaped
curve located between the coronoid
and condylar processes
Facial bones

24. • Mylohyoid line— bony ridge extends along
the inner aspect of the mandibular body,
attachment of the muscle that forms the floor
of the oral cavity
• Mandibular foramen— opening is located on
the medial side of the ramus of the mandible.
• leads into a tunnel that runs down the
length of the mandibular body.
• sensory nerve and blood vessels that
supply the lower teeth enter the
mandibular foramen and then follow this
tunnel.
• Lingula—small flap of bone located
immediately next to the mandibular foramen,
on the medial side of the ramus.
• ligament that anchors the mandible
during opening and closing of the mouth
extends down from the base of the skull
and attaches to the lingula.
Facial bones

25. • Body of the Mandible
• Alveolar process of the
mandible— upper border of the
mandibular body and serves to
anchor the lower teeth.
• Mental protuberance— forward
projection from the inferior margin
of the anterior mandible that
forms the chin
• Mental foramen— opening
located on each side of the
anterior-lateral mandible, exit site
for a sensory nerve that supplies
the chin.
Facial bones

26. • Anterior cranial fossa - most
anterior and the shallowest of
the three cranial fossae.
• Boundaries:
• Anterior: Frontal bone - forms
mainly the floor for this space.
• Posterior: Lesser wings of the
sphenoid bone - form the
prominent ledge that marks the
boundary.
• Midline: Crista galli and
Cribriform plates.
Floor/Base of Cranial Cavity

27. • Middle cranial fossa - deeper
and situated posterior to the
anterior fossa
• Boundaries:
• Anteriorly: Lesser wings of the
sphenoid bone
• Posteriorly: Petrous ridges
(petrous portion of the temporal
bones).
• Midline: Sella turcica
Floor/Base of Cranial Cavity

28. • Optic canal— opening is located at the
anterior lateral corner of the Sella turcica ,
provides for passage of the optic nerve into
the orbit.
• Superior orbital fissure— large, irregular
opening in the lesser wing of sphenoid into
the posterior orbit, provides passage to the
nerves to the eyeball and associated
muscles, and sensory nerves to the
forehead.
• Foramen rotundum— rounded opening
located in the greater wing of sphenoid, just
inferior to the superior orbital fissure, exit
point for a major sensory nerve that supplies
the cheek, nose, and upper teeth.
• Foramen ovale — large, oval-shaped
opening in the base of greater wing of
sphenoid, provides passage for a major
sensory nerve to the lateral head, cheek,
chin, and lower teeth.
Floor/Base of Cranial Cavity

29. • Foramen spinosum— small opening, located
posteromedial part of greater wing of
sphenoid bone posterolateral to foramen
ovale, entry point for an important artery that
supplies the covering layers surrounding the
brain
• Carotid canal— located on the inferior aspect
of the skull, anteromedial to the styloid
process, passageway through which a major
artery to the brain enters the skull,
• Foramen lacerum— irregular opening located
in the between the sphenoid bone, apex of
petrous temporal and basilar part of occipital,
immediately inferior to the exit of the carotid
canal
• artifact of the dry skull-filled with
cartilage, nothing passes this foramen
Floor/Base of Cranial Cavity

30. • Posterior cranial fossa - most
posterior and deepest portion of
the cranial cavity
• contains the cerebellum of the brain.
• Boundaries:
• Anterior: Petrous ridges of Temporal
bone
• Floor: Occipital bone
• Posterior: Foramen magnum (“great
aperture”) the opening that provides
for passage of the spinal cord.
Floor/Base of Cranial Cavity

31. • Internal acoustic meatus - Located on the
medial wall of the petrous ridge in the
posterior cranial fossa, provides for
passage of the nerve from the hearing
and equilibrium organs of the inner ear,
and the nerve that supplies the muscles
of the face
• Hypoglossal canal – located in the
inferior aspect of the skull at the base of
the occipital condyle, provide passage for
an important nerve to the tongue.
• Jugular foramen – large irregularly
shaped located inferior to the internal
acoustic meatus, provides opening for the
exit of several cranial nerves from the
brain and exit point through the base of
the skull for all the venous return blood
leaving the brain.
Floor/Base of Cranial Cavity