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The Skeleton

For descriptive purposes, the skeleton is divided into:

Axial Skeleton

Appendicular Skeleton
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The Axial Skeleton

Structured from eighty bones segregated into three
regions:

Skull

Vertebral column

Bony thorax
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Axial Skeleton


Supports the:

Head

Neck

Trunk
Protects the:

Brain

spinal cord

Organs in the thorax
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Bones of the Axial Skeleton
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Figure 7.1
The Skull

Most complex bony structure

Formed by two groups of 22 bones :

The cranial bones or cranium

Facial bones
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The Cranium

Made of 8 bones

Encloses and protects the brain

Furnish attachment sites for:

Head muscles

Neck muscles
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Anatomy of the Cranium

Eight cranial bones (Thin and remarkably strong for their weight):


Paired:

Two parietal

Two temporal
Unpaired:

Frontal

Occipital

Sphenoid

Ethmoid
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Frontal Bone
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Figure 7.2a
Frontal Bone

Forms anterior portion of the cranium

Articulates posteriorly with the parietal bones via:


The coronal suture (joint)
Major markings:

The supraorbital margins

The supraorbital foramen

The anterior cranial fossa

The frontal sinuses
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Frontal Bone
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Figure 7.2a
Frontal Sinuses:
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Figure 7.11
Parietal Bones

Two large, curved, & rectangular bones

Form most of :


The superior aspect of the skull, and

The lateral aspects of the skull
Articulate with:

other cranial bones through:

Four large sutures (joints)
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Parietal Bones & Major Associated Sutures

The four sutures marking the articulations of the
parietal bones include:

Coronal suture: between parietal and frontal bones,
anteriorly

Sagittal suture: between right and left parietal bones,
superiorly

Lambdoid suture: between parietal and occipital bone,
posteriorly

Squamous suture: where parietal and temporal bones
meet
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Parietal Bones and Major Associated Sutures

Form most of the superior and lateral aspects of the
skull
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Figure 7.3a
Occipital Bone and Its Major Markings


Forms most of skull’s
posterior wall and base
Major markings:

The posterior cranial
fossa

Foramen magnum

Occipital condyles

External occipital
protuberance
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Figure 7.2b
Temporal Bones



Form:

The inferolateral aspects of the skull

Parts of the cranial floor
Divided into four major regions:

Squamous (bordering the parietals)

Tympanic (surrounds ext. ear opening)

Mastoid (posterior to ear)

Petrous (lateral portion of skull base)
Major markings:

Zygomatic, styloid, and mastoid processes

Mandibular fossa and external acoustic meatus
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Temporal Bones
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Figure 7.5
Sphenoid Bone

Butterfly-shaped bone

Spans the width of the middle cranial fossa

Central wedge that articulates with all other cranial bones

Consists of central body & three paired processes:

Central body: contains paired sinuses

Greater wings: forms part of middle cranial fossa, dorsal walls
of orbit, and skull wall

Lesser wings: forms part of anterior cranial fossa and medial
walls of orbit

Pterygoid processes: projects ineriorly and forms attachment
site for pterygoid muscles (chewing)
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Sphenoid Bone

Major markings:


Sella turcica (pituitary gland location)
Major openings:

Optic canals

Superior orbital fissure

Foramen rotundum

Foramen ovale

Foramen spinosum
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
Break

Biol2401.5039Oct 3rd
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Sphenoid Bone
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Figure 7.6a
Sphenoid Bone
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Figure 7.6b
Ethmoid Bone

Lies between the sphenoid and nasal bones

Forms:


most of the bony area between the nasal cavity and
the orbits
Major markings:

Perpendicular plate

Lateral masses (riddled with ethmoid sinuses)

Nasal conchae (superior & middle)
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Ethmoid Bone
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Figure 7.7
Sutural (Wormian) Bones

Tiny irregularly
shaped bones

Appear within sutures

Unknown functiom
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Facial Bones

Form the framework of the face

Contain cavities for special senses (sight, smell, taste)

Provide passageways for air and food

Secure teeth

Attachment site for facial muscles of expression

Made of 14 bones
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Facial Bones


Unpaired (two):

Mandible

Vomer
Paired (six):

Maxillae

Zygomatics

Nasals

Lacrimals

Palatines

Inferior conchae
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Mandible and Its Markings

The lower jaw bone

largest, strongest bone of the face

Its major markings:

Coronoid process

Mandibular condyle

Alveolar margin

Mandibular foramen

Mental foramina
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Mandible and Its Markings
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Figure 7.8a
Maxillary Bones

Medially fused bones

Make up:


Articulate with:


The upper jaw
All other facial bones except the mandible
Major markings:

Palatine, frontal, and zygomatic processes

Alveolar margins

Inferior orbital fissure (junction with sphenoid greater wing)

Maxillary sinuses (largest of paranasal sinuses)
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Maxillary Bone
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Figure 7.8b
Paranasal Sinuses: Maxillary Sinuses
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Figure 7.11
Zygomatic Bones (cheekbones)

Irregularly shaped bones

Form:


The prominences of the cheeks

The inferolateral margins of the orbits
Articulate with the zygomatic processes of the:

Frontal bone (superiorly)

Maxillae (anteriorly)

Temporal bones (posteriorly)
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Other Facial Bones


Nasal bones:

Thin medially fused bones

Form the bridge of the nose
Lacrimal bones:

Contribute to the medial walls of the orbit

Contain a deep groove – the lacrimal fossa

The lacrimal fossa houses the lacrimal sac
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Other Facial Bones

Palatine bones:

Each is an L-shaped bone of two bony plates

One is horizontal and the other is perpendicular

Form:

The posterior portions of the hard palate

Part of posterolateral walls of the nasal cavity

Small part of the orbits
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Other Facial Bones


Vomer:

Plow-shaped bone

Forms part of the nasal septum
Inferior nasal conchae:

Paired, curved bones

In the nasal cavity

Form part of the lateral walls of the nasal cavity
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Orbits

Bony cavities where eyes are firmly encased

Eyes are cushioned by fatty tissue

Formed by parts of seven (3 cranial & 4 facial) bones:

Frontal

Sphenoid

Ethmoid

Zygomatic

Maxilla

Palatine

Lacrimal
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Orbits
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Figure 7.9b
Nasal Cavity

Constructed of bone and hyaline cartilage

Roof formed by:



Cribriform plate of the ethmoid
Lateral walls formed by:

Superior and middle conchae of the ethmoid

Perpendicular plate of the palatine

Inferior nasal conchae
Floor formed by:

Palatine process of the maxillae and palatine bone
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Nasal Cavity
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Figure 7.10a
Nasal Cavity
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Figure 7.10b
Paranasal Sinuses

They are mucosa-lined, air-filled sacs

Found in five skull bones:

Frontal

Sphenoid

Ethmoid

Paired Maxillae

Air enters the paranasal sinuses from the nasal cavity

Mucus drains into the nasal cavity from the sinuses

They:

Lighten the skull

Enhance the resonance of the voice
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Paranasal Sinuses
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Figure 7.11
Hyoid Bone

Not actually part of the skull

Lies just inferior to the mandible in the anterior neck

Only bone does not articulate directly with another bone

Anchors to styloid process of temporal bone by stylohyoid ligament

Attachment point for neck muscles that raise and lower
the larynx during:

Swallowing

Speech
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The Following Slide Are:
Only for Reinforcement
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Anterior Aspects of the Skull
Frontal bone
Parietal bone
Glabella
Frontonasal suture
Frontal squama
of frontal bone
Supraorbital foramen
(notch)
Nasal bone
Supraorbital margin
Superior orbital
fissure
Optic canal
Sphenoid bone
(greater wing)
Temporal bone
Ethmoid bone
Inferior orbital
fissure
Lacrimal bone
Zygomatic bone
Middle nasal concha
Perpendicular plate
Infraorbital foramen
Maxilla
Ethmoid
bone
Inferior nasal concha
Vomer bone
Mandible
Mental
foramen
(a)
Mandibular symphysis
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Figure 7.2a
Posterior Aspects of the Skull
Sagittal suture
Parietal bone
Sutural
bone
Lambdoid
suture
Occipital bone
Superior nuchal line
External
occipital
protuberance
Occipitomastoid
suture
(b)
Mastoid
process
External
occipital
crest
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Occipital
condyle
Inferior
nuchal
line
Figure 7.2b
External Lateral Aspects of the Skull
Coronal suture
Frontal bone
Sphenoid bone
(greater wing)
Parietal bone
Ethmoid bone
Temporal bone
Lacrimal bone
Lambdoid
suture
Lacrimal fossa
Squamous suture
Nasal bone
Occipital bone
Zygomatic process
Zygomatic bone
Occipitomastoid suture
Maxilla
External acoustic meatus
Mastoid process
Alveolar margins
Styloid process
Mandibular condyle
Mandible
Mental foramen
Mandibular notch
Mandibular ramus
(a)
Mandibular angle
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Coronoid process
Figure 7.3a
Midsagittal Lateral Aspects of the Skull
Parietal bone
Coronal suture
Squamous
suture
Frontal bone
Temporal
bone
Sphenoid bone
(greater wing)
Frontal sinus
Crista galli
Lambdoid suture
Nasal bone
Sphenoid sinus
Ethmoid bone
(perpendicular plate)
Vomer bone
Incisive fossa
Occipital
bone
Occipitomastoid
suture
External occipital
protuberance
Maxilla
Alveolar margins
Internal acoustic
meatus
(b)
Sella turcica
of sphenoid
bone
Pterygoid
process of
sphenoid Mandibular
foramen
bone
Mandible
Palatine
bone Palatine
process of
maxilla
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Figure 7.3b
Inferior Portion of the Skull
Maxilla
(palatine process)
Hard
palate
Palatine bone
(horizontal plate)
Zygomatic bone
Temporal bone
(zygomatic process)
Vomer
Maxilla
Sphenoid bone
(greater wing)
Foramen ovale
Foramen
lacerum
Carotid canal
Mandibular
fossa
External acoustic meatus
Styloid process
Mastoid process
Temporal bone
(petrous part)
Pharyngeal
tubercle of
basioccipital
Parietal bone
External occipital crest
(a)
Incisive fossa
Medial palatine suture
Infraorbital foramen
External occipital
protuberance
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Stylomastoid
foramen
Jugular foramen
Occipital condyle
Inferior nuchal line
Superior nuchal line
Foramen magnum
Figure 7.4a
Inferior Portion of the Skull
Olfactory foramina
Frontal bone
Anterior cranial fossa
Cribriform plate
Crista galli
Sphenoid
Lesser wing
Greater wing
Ethmoid
bone
Optic canal
Anterior clinoid process
Foramen rotundum
Tuberculum sellae
Hypophyseal fossa
Sella
Dorsum sellae
turcica Posterior clinoid process
Foramen ovale
Foramen spinosum
Middle cranial
fossa
Temporal bone
(petrous part)
Foramen lacerum
Jugular foramen
Hypoglossal canal
Internal
acoustic meatus
Posterior
cranial fossa
Anterior
cranial
fossa
Parietal bone
Occipital bone
(b)
Middle
cranial
fossa
Foramen magnum
(c)
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Posterior
cranial
fossa
Figure 7.4b