Download The Axial Skeleton Eighty bones segregated into three regions

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 (22 in
all)
Cranium
Made up of cranial bones
protects the brain and is the site of attachment for
head and neck muscles
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Facial bones
Facial bones
Form the framework of the face
Contain cavities for special sense organs (smell,
sight, taste, hearing)
Provide openings for the passage of air and food
Secure the teeth
Anchor the facial muscles of expression
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Bones of the Skull
Most of the bone of the skull are flat bones
All of the bones of the skull are tightly united by
sutures (interlocking joints)…except the mandible
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Major Skull Sutures
Sutures of the skull connect the cranial bones
The major sutures of the skull are:
Coronal
Sagittal
Squamous
Lambdoid
w/ other sutures connecting the facial bones
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Overview of Skull Geography
The cranium can be divided into a vault and a base
The cranial vault (calvarin) forms the superior,
lateral, and posterior aspects of the skull (and
forehead)
The cranial base (floor) forms the skull’s inferior
aspect
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Overview of Skull Geography
The internal bony ridges divide the base into 3
steps (or fossae):
Anterior cranial fossae
Middle cranial fossae
Posterior cranial fossae
The brain sits within these 3 cranial fossae
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Overview of Skull Geography
Other cavities include:
Middle & internal ear cavities
Nasal cavity
Orbits
sinuses
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Anatomy of the Cranium
Eight cranial bones
Parietal (2)
Temporal (2)
Frontal
Occipital
Sphenoid
Ethmoid
The curvatures of the cranial bones makes them strong and
allows them to be thin (e.g. an eggshell)
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Frontal Bone
Forms the anterior portion of the cranium
Articulates posteriorly with the paired parietal bones via the coronal
suture
Most anterior part is the vertical frontal squama (otherwise known as the
“forehead”)
The frontal squama ends inferiorly at the supraorbital margins
The supraorbital margin is pierced by the supraorbital foramen
allowing passage of the supraorbital artery and nerve to the
forehead
Extending posteriorly, the frontal bone forms the superior wall of the
orbits and the anterior cranial fossa
The glabella is the smooth part of the bone between the orbits
The frontonasal suture joins the glabella and the nasal bones
The frontal sinuses are found deep and lateral to the glabella
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Frontal Bone
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Figure 7.2a
Parietal Bones and Major Associated Sutures
The parietal bones form the superior and lateral aspects of the
skull
They make up the bulk of the cranial vault
The 4 largest sutures are associated with 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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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
The occipital bone forms most of the skulls posterior wall and base
It articulates anteriorly w/ the paired parietal and temporal bones via the
lambdoid and occipitomastoid sutures, respectively
It articulates w/ the sphenoid bone via the basioccipital plate
Internally, the occipital bone forms the walls of the posterior cranial fossa
The foramen magnum found at the base of the occipital bone if where the
inferior part of the brain connects with the spinal cord
The occipital condyles flank the foramen magnum laterally and articulate w/
the first vertebra permitting a “nodding” movement
The external occipital proturbence (can you feel yours??)
External occipital crest: secures the legamentum nuchae (an elastic ligament
that connects the vertebrae to the skull)
Superior & inferior nuchal lines: anchor many muscles of the neck & back
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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
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Figure 7.5
Temporal Bones
Lie inferior to the parietal bones and join them at
the squamous sutures
Form the inferolateral aspects of the skull and parts
of the cranial floor
Divided into four major regions
Squamous
Tympanic
Mastoid
petrous
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Temporal Bones: Squamous Region
The squamous region has the bar-like zygomatic
process that meets the zygomatic bone forming the
zygomatic arch (the cheek bone)
The mandibular fossa on the inferior surface of the
zygomatic process receives the condyle of the
mandible (lower jawbone) forming the
temporomandibular joint
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Temporal Bones: Tympanic Region
The Tympanic region surrounds the external
acoustic meatus (external ear canal)
Inferior to the exteranl acoustic meatus lies the
styloid process, an attachment point for several
tongue and neck muscles
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Temporal Bones: Mastoid Region
The mastoid region contains the large mastoid
process which anchors some neck muscles
Feel it right behind your ear…go ahead, feel it!
The stylomastoid foramen allows cranial nerve VII
(the facial nerve) to leave the skull
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Temporal Bones: Petrous Region
The petrous region contributes to the cranial base
It lies between the occipital bone and the sphenoid
bone
Together w/ the sphenoid bone they form the
middle cranial fossa which supports the temporal
lobes of the brain
This region also houses the middle & internal ear
cavities
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Temporal Bones: Petrous Region
Several foramen penetrate the petrous region:
-the jugular foramen: internal jugular & 3 cranial nerves
-the carotid canal: internal carotid artery
-the foramen lacerum
-the internal acoustic meatus: cranial nerves VII & VIII
-the foramenia rotundum, ovale, and spinosum
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Sphenoid Bone
Butterfly-shaped bone that spans the width of the
middle cranial fossa
The Keystone Bone: Forms the central wedge that
articulates with all other cranial bones
Consists of a central body, greater wings, lesser
wings, and pterygoid processes
Contains the sphenoid sinuses
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Sphenoid Bone
The superior surface bears the sella tucica which
bears the hypophyseal fossa that forms the
enclosure for the pituitary gland
The hypophyseal fossa is abutted anteriorly by the
tuberculum sellae and posteriorly by the dorsum
sellae, which terminates in the posterior clinical
processes
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Sphenoid Bone
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Figure 7.6a
Sphenoid Bone
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Figure 7.6b
Sphenoid Bone
The greater wings project laterally from the body and form:
Middle cranial fossa
Dorsal walls of the orbits
External wall of the skull (medial to the zygomatic arch)
The lesser wings form:
Part of the floor of the anterior cranial fossa
Part of the medial walls of the orbits
Terminate medially at the anterior clinoid process (an anchoring site
for the brain)
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Sphenoid Bone
The pterygoid processes project inferior from the body.
Function to anchor the pterygoid muscles that we use when we
chew
Openings in the sphenoid bone:
Optic canals: connected by the optic chiasmatic groove.
Allow the optic nerves to pass
Superior orbital fissure: Allow the passage of cranial nerves
III, IV, and VI which control eye movement
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Sphenoid Bone
More openings in the sphenoid bone:
Foramen rotundum:
Foramen ovale:
Branch of cranial nerve V for the maxillary nerve
Branch of cranial nerve V for the mandibullar nerve
Foramen spinosum:
Transmits the middle meningreal artery that serves internal
faces of some cranial bones
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Ethmoid Bone
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Figure 7.7
Ethmoid Bone
Deepest of the skull bones; lies between the sphenoid and nasal
bones
Forms most of the bony area between the nasal cavity and the
orbits
The cribiform plates (seen from above) form the roof of the
nasal cavities and the floor of the anterior cranial fossa
The olfactory foramina: allow the olfactory nerves to pass
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Ethmoid Bone
Crista galli: (triangular process)
Attachment site for the dura mater (the
outermost covering of the brain)
Perpendicular plate
Projects inferiorly in the median plane
Forms the superior part of the nasal septum
(which divides the nasal cavity right and left)
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Ethmoid Bone
Right & left lateral masses:
Superior/middle nasal conchae (turbinates)
Riddled w/ ethmoid sinuses (acts as sieve)
Protrude into the nasal cavity
Orbital plate:
Located on the lateral surfaces of the lateral masses
Contribute to the medial walls of the orbits
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Wormian Bones
Tiny irregularly shaped bones that appear within
sutures
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Facial Bones
14 bones (6 paired sets) of which only the mandible and
vomer are unpaired
The paired bones are:
Maxillae
Zygomatics
Nasals
Lacrimals
Palatines
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
Mandible and Its Markings
The mandible (lower jaw) is the largest, strongest bone of the
face
The body forms the chin
The rami meet the body posteriorly at a mandibular angle
The mandibular notch separates the coronoid and condyle
processes or the rami
The coronoid process (anterior) is the insertion point for the
large temporalis muscle that elevates the lower jaw during
chewing
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Mandible and Its Markings
The mandibular condyle (posterior) articulates
with the mandibular fossa of the temporal bone
forming the temporomandibular joint
Mandibular body anchors the teeth
Alveolar margin: the superior border of the body
contains the sockets win which the teeth are
embedded
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Mandible and Its Markings
Mandibular symphysis:
Site of fusion of the two mandibular bones ( in infancy)
Mandibular foramina
Found on the medial surface of each ramus
Nerve passage for tooth sensation (injection site for
Lidocaine)
Mental foramina:
Lateral aspects of body
Allow blood vessels and nerves to pass to skin of the
chin
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Maxillary Bone
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Figure 7.8b
Maxillary Bones (maxillae)
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
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Maxillary Bones: Major Markings
Alveolar margins:
Anterior nasal spine:
Carry the upper teeth
Site of fusion of maxillae (inferior to nose)
Palatine processes:
Project posteriorly from the alveolar margins
Fuse medially forming the anterior 2/3 of the hard palate
or bony roof of the mouth
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Maxillary Bones: Major Markings
Incisive fossa (midline foramen)
Posterior to teeth
Passage for blood vessels/nerves
Maxillary sinuses
Largest of the paranasal sinuses
Extend from the orbits to the roots of the upper teeth
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Maxillary Bones: Major Markings
Zygomatic processes:
Lateral articulation between the maxillae and zygomatic
bones
Inferior orbital fissure:
Located deep within the orbit at the junction of the
maxilla and the greater wings of the sphenoid
Permits zygomatic nerve, maxillary nerve (cranial nerve
V branch) and blood vessels to pass to the face
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Maxillary Bones: Major Markings
Infraorbital foramen:
Allows the infraorbital nerve (a continuation of
the maxillary nerve) and artery to reach the face
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Zygomatic Bones
Irregularly shaped bones (cheekbones)
Articulate with the zygomatic processes of the
temporal bones posteriorly, the zygomatic process
of the frontal bone superiorly, and the zygomatic
process of the maxillae anteriorly
For part of 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
Articulate with the frontal bone superiorly, the maxillary
bones laterally, and the perpendicular plate of the
ethmoid bone posteriorly
Cartilages form the “skeleton” of the external nose
inferiorly
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Other Facial Bones
Lacrimal bones:
Contribute to the medial walls of the orbit
Smallest and most fragile of the facial bones
Articulate with the frontal bone superiorly, ethmoid bone
posteriorly, and the maxillae anteriorly
Contains a deep groove (lacrimal fossa) that houses the lacrimal
sac that is part of the passage that allows tears to drain from the
eye to the nasal cavity
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Other Facial Bones
Palatine bones:
Fashioned from 2 bony plates
Horizontal: complete posterior portion of the hard palate
Perpendicular: forms the posterior walls of the nasal
cavity and the small parts of the orbits
3 articulating processes:
Pyramidal
Sphenoidal
orbital
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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
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)
Ethmoid
bone
Middle
cranial
fossa
Foramen magnum
(c)
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Posterior
cranial
fossa
Figure 7.4b