Download Copyright © 2006 Pearson Education, Inc., publishing as Benjamin

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
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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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 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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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: minor artery, nerve, vein
-the internal acoustic meatus: cranial nerves VII & VIII
-the foramenia rotundum, ovale, and spinosum: passage
For arteries, nerves, veins
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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 turcica which
bears the hypophyseal fossa that forms the
enclosure for the pituitary gland (hypophysis)
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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 (see arrows)
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. Circulate air w/i nasal
passages
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
Most sources include:
Maxillae
Zygomatics
Nasals
Lacrimals
Palatines
inferior nasal conchae
Vomer
Mandible
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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 (passage of
nerves and vessels)
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Mandible and Its Markings
The body forms the chin
The rami meet the body posteriorly at the 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 w/i 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
Form 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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Orbits
Bony cavities in which the eyes are firmly encased and
cushioned by fatty tissue
Formed by parts of seven bones:
Frontal
Sphenoid
Zygomatic
Maxilla
Palatine
Lacrimal
ethmoid
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Orbits
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Figure 7.9b
Nasal Cavity
Constructed of bone and hyaline cartilage
Roof – formed by the cribriform plate of the
ethmoid
Lateral walls – formed by the superior and middle
conchae of the ethmoid, the perpendicular plate of
the palatine, and the 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 7.10b
Nasal Cavity
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Figure 7.10a
Paranasal Sinuses
Mucosa-lined, air-filled sacs found in five skull bones:
Frontal
Sphenoid
Ethmoid
Paired maxillary bones
Air enters the paranasal sinuses from the nasal cavity and
mucus drains into the nasal cavity from the sinuses
Lighten the skull and enhance the resonance of the voice
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Paranasal Sinuses
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