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Chapter 7: Skeletal System,
Axial Skeleton
The Axial Skeleton

Eighty bones segregated into three regions

Skull

Vertebral column

Bony thorax
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Bones of the Axial Skeleton
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Figure 7.1
The Skull



The skull, the body’s most complex bony structure,
is formed by the cranium and facial bones
Cranium – protects the brain and is the site of
attachment for head and neck muscles
Facial bones

Supply the framework of the face, the sense
organs, and the teeth

Provide openings for the passage of air and food

Anchor the facial muscles of expression
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Anatomy of the Cranium


Eight cranial bones – two parietal, two temporal,
frontal, occipital, sphenoid, and ethmoid
Cranial bones are thin and remarkably strong for
their weight
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Frontal Bone

Forms the anterior portion of the cranium

Articulates posteriorly with the parietal bones via
the coronal suture

Major markings include the supraorbital margins,
the anterior cranial fossa, and the frontal sinuses
(internal and lateral to the glabella)
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Frontal Bone
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Figure 7.2a
Parietal Bones and Major Associated Sutures

Form most of the superior and lateral aspects of the
skull
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Figure 7.3a
Parietal Bones and Major Associated Sutures

Four sutures mark the articulations of the parietal
bones




Coronal suture – articulation between parietal
bones and frontal bone anteriorly
Sagittal suture – where right and left parietal bones
meet superiorly
Lambdoid suture – where parietal bones meet the
occipital bone posteriorly
Squamosal or squamous suture – where parietal
and temporal bones meet
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Occipital Bone and Its Major Markings

Forms most of skull’s
posterior wall and base

Major markings
include the posterior
cranial fossa, foramen
magnum, occipital
condyles, and the
hypoglossal canal
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Figure 7.2b
Temporal Bones



Form the inferolateral aspects of the skull and parts
of the cranial floor
Divided into four major regions – squamous,
tympanic, mastoid, and petrous
Major markings include the zygomatic, styloid,
and mastoid processes, and the mandibular and
middle cranial fossae
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Temporal Bones

Major openings include the stylomastoid and
jugular foramina, the external and internal auditory
meatuses, and the carotid canal
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Temporal Bones
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Figure 7.5
Sphenoid Bone

Butterfly-shaped bone that spans the width of the
middle cranial fossa

Forms the central wedge that articulates with all
other cranial bones

Consists of a central body, greater wings, lesser
wings, and pterygoid processes
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Sphenoid Bone

Major markings: the sella turcica, hypophyseal
fossa, and the pterygoid processes

Major openings include the foramina rotundum,
ovale, and spinosum; the optic canals; and the
superior orbital fissure
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Sphenoid Bone
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Figure 7.6a
Sphenoid Bone
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Figure 7.6b
Ethmoid Bone

Most deep of the skull bones; lies between the
sphenoid and nasal bones

Forms most of the bony area between the nasal
cavity and the orbits

Major markings include the cribriform plate, crista
galli, perpendicular plate, nasal conchae, and the
ethmoid sinuses
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Ethmoid Bone
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Figure 7.7
Wormian Bones

Tiny irregularly shaped bones that appear within
sutures
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Facial Bones

Fourteen bones of which only the mandible and
vomer are unpaired

The paired bones are the maxillae, zygomatics,
nasals, lacrimals, palatines, and inferior conchae
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Mandible and Its Markings

The mandible (lower jawbone) is the largest,
strongest bone of the face

Its major markings include the coronoid process,
mandibular condyle, the alveolar margin, and the
mandibular and mental foramina
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Mandible and Its Markings
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Figure 7.8a
Maxillary Bones

Medially fused bones that make up the upper jaw
and the central portion of the facial skeleton

Facial keystone bones that articulate with all other
facial bones except the mandible

Their major markings include palatine, frontal, and
zygomatic processes, the alveolar margins, inferior
orbital fissure, and the maxillary sinuses
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Maxillary Bone
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Figure 7.8b
Zygomatic Bones

Irregularly shaped bones (cheekbones) that form
the prominences of the cheeks and the inferolateral
margins of the orbits
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Other Facial Bones



Nasal bones – thin medially fused bones that form
the bridge of the nose
Lacrimal bones – contribute to the medial walls of
the orbit and contain a deep groove called the
lacrimal fossa that houses the lacrimal sac
Palatine bones – two bone plates that form portions
of the hard palate, the posterolateral walls of the
nasal cavity, and a small part of the orbits
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Other Facial Bones


Vomer – plow-shaped bone that forms part of the
nasal septum
Inferior nasal conchae – paired, curved bones in
the nasal cavity that form part of the lateral walls
of the nasal cavity
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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