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Karen Dunbar KareivaIvy Tech Community College© Annie Leibovitz/Contact Press Images

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Chapter 7 Part A

The Skeleton

Why This Matters• Understanding the anatomy of the skeleton enables you to

anticipate problems such as pelvic dimensions that may affect labor and delivery

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The Skeleton• The skeletal system, or skeleton, is composed of bones, cartilages,

joints, ligaments• Mostly bone• Cartilage occurs in isolated areas• Ligaments connect bones and reinforce joints

• The skeleton accounts for 20% of body mass• Two major divisions

• Axial skeleton• Appendicular skeleton

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Part 1: The Axial Skeleton• Axial skeleton consists of 80 bones divided into three major regions:

• Skull• Vertebral column• Thoracic cage

• Axial skeleton has three functions:1. Form longitudinal axis of body2. Support head, neck, and trunk3. Protect brain, spinal cord, and thoracic organs

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Figure 7.1a The human skeleton.

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Cranium

Facial bones

Clavicle

Scapula

SternumRibHumerus

VertebraRadiusUlna

Carpals

PhalangesMetacarpalsFemurPatella

Tibia

Fibula

TarsalsMetatarsalsPhalanges

Skull

Thoracic cage(ribs, sternumand thoracicvertebrae)

Vertebralcolumn

Sacrum

Anterior view

Figure 7.1b The human skeleton.

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Cranium

Clavicle

Scapula

RibHumerus

VertebraRadiusUlna

Carpals

PhalangesMetacarpalsFemur

Tibia

Lowerlimb

Bones ofpelvic girdle

Upperlimb

Bones ofpectoralgirdle

Posterior view

Fibula

7.1 The Skull• Skull is most complex bony structure in body• Formed by two sets of bones:

1. Cranial bones (cranium) • Enclose the brain in the cranial cavity • Provide sites of attachment for head and neck muscles

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7.1 The Skull2. Facial bones

• Form framework of face• Contain cavities for special sense organs for sight, taste, and smell• Provide openings for air and food passage• Secure teeth• Anchor facial muscles used for facial expression

• Most skull bones are flat and firmly locked together (except for mandible)• Joints are called sutures

• Have a serrated, saw-tooth appearance

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Figure 7.2a The skull.

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Bones of cranium

Coronalsuture

Squamoussuture

Facialbones

Lambdoidsuture

Cranial and facial divisions of the skull

Overview of Skull Geography• Facial bones form anterior aspect, with cranium forming the rest of

skull• Cranium is divided into a vault and a base

• Cranial vault (calvaria) forms superior, lateral, and posterior portion of skull, as well as forehead

• Cranial base forms inferior aspect of skull• Internally base is divided into three “steps,” or fossae: anterior, middle, posterior fossae• Brain sits within these fossae, enclosed by cranium vault

• Area referred to as cranial cavity

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Figure 7.2b The skull.

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Anterior cranialfossa

Middle cranialfossa

Posterior cranialfossa

Superior view of the cranial fossae

Figure 7.2c The skull.

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Frontal lobeof cerebrum

Temporal lobeof cerebrumCerebellum

PosteriorMiddleAnterior

Cranialfossae

Lateral view of cranial fossae showing thecontained brain regions

Overview of Skull Geography (cont.)• Cranium also contains other cavities:

• Middle and internal ear cavities• Nasal cavity• Orbits that house eyeballs

• Skull has 85 named openings• Foramina, canals, fissures• Provide passageways for spinal cord, major blood vessels, and the 12 cranial

nerves

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Figure 7.3 Major cavities of the skull, frontal section.

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Frontalbone

ZygomaticboneEthmoidboneInferior nasalconchaMaxillaVomerMandible

Oral cavity

OrbitOrbit

Cranial cavity

FrontalsinusEthmoidalair cellsMaxillarysinusNasalcavity

Cranium• Cranium is comprised of eight cranial bones:

• Frontal bone• Parietal bones (two—left and right)• Occipital bone• Temporal bones (two—left and right)• Sphenoid bone• Ethmoid bone

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Cranium (cont.)• Frontal bone: shell-shaped bone forms anterior portion of cranium

• Vertical part, called squamous region, is also known as the forehead• Inferior portion ends at supraorbital margins

• Area underneath eyebrows• Forms superior wall of the orbits and most of anterior cranial fossa• Supraorbital foramen (notch) allows supraorbital artery and nerve to pass to

forehead• Glabella is area of frontal bone between orbits

• Frontal sinuses located just lateral to glabella

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Figure 7.4a Anterior and posterior views of the skull.

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Parietal bone

Nasal bone

Temporal boneEthmoid boneLacrimal boneZygomatic bone

MaxillaInfraorbital foramen

Mandible

Anterior view

Frontal boneGlabellaFrontonasal sutureSupraorbital foramen (notch)

Supraorbital marginSuperior orbital fissure

Inferior orbital fissure

Middle nasal concha

Inferior nasal conchaVomer

Optic canal

Perpendicular plate Ethmoid bone

Mandibularsymphysis

Mentalforamen

Sphenoid bone(greater wing)

Squamous part of frontal bone

Figure 7.7a The base of the cranial cavity.

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Cribriform foraminaLesser wingSphenoid

Anterior cranial fossa

Occipital bone

Superior view of the skull, calvaria removed

Greater wing

ViewCrista galli

Optic canal

Foramen rotundumForamen ovaleForamen spinosum

Jugular foramen

Hypoglossal canal

Foramen lacerumInternal acoustic meatus

Hypophyseal fossaof sella turcica

Middle cranialfossaTemporal bone(petrous part)

Posteriorcranial fossa

Frontal boneEthmoidbone

Parietal bone

Foramen magnum

Cribriform plate

Figure 7.7b The base of the cranial cavity.

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View Frontal boneCribriform foramina

Lesser wingSphenoid

Anterior cranial fossa

Parietal boneOccipital bone

Foramen magnumPhoto of superior view of the skull, calvaria removed

Greater wing

Cribriform plateCrista galli

Optic canal

Foramen rotundumForamen ovaleForamen spinosum

Jugular foramen

Foramen lacerum

Hypophyseal fossaof sella turcica

Middle cranialfossaTemporal bone(petrous part)

Posteriorcranial fossa

Ethmoidbone

Cranium (cont.)• Parietal bones and the major sutures

• Two large parietal bones form most of superior and lateral aspects of cranial vault

• Four sutures mark articulations of parietal bones with frontal, occipital, and temporal bones:

1. Coronal suture: between parietal bones and frontal bone

2. Sagittal suture: between right and left parietal bones

3. Lambdoid suture: between parietal bones and occipital bone

4. Squamous (squamosal) sutures: between parietal and temporal bones on each side of skull

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Figure 7.2a The skull.

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Bones of cranium

Coronalsuture

Squamoussuture

Facialbones

Lambdoidsuture

Cranial and facial divisions of the skull

Figure 7.4b Anterior and posterior views of the skull.

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Parietal bone Sagittal suture

Occipital bone

Suturalbone

Lambdoidsuture

Superior nuchallineExternaloccipitalprotuberanceOccipitomastoidsuture External

occipital crestOccipitalcondyle

Inferiornuchalline

Mastoidprocess oftemporalbone

Figure 7.5a Bones of the lateral aspect of the skull, external and internal views.

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Coronal suture

Lambdoid suture

Occipital bone

Occipitomastoid suture

External acoustic meatusMastoid processStyloid process

Zygomatic process

Squamous suture

Condylar processMandibular notchMandibular ramus

Mandibular angle Coronoid process

Ethmoid boneLacrimal bone

Lacrimal fossa

Nasal bone

Maxilla

Alveolar processes

MandibleMental foramen

Parietal bone

Temporal bone

External anatomy of the right sideof the skull

Frontal bone

Zygomatic bone

Sphenoid bone(greater wing)

Figure 7.5b Bones of the lateral aspect of the skull, external and internal views.

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Condylar process

Coronal suture

Parietal bone

Lambdoid suture

Squamous suture

Occipital bone

Mastoid processStyloid process

Mandibular angle

Zygomatic processTemporal bone

Frontal bone

Ethmoid boneLacrimal bone

Lacrimal fossa

Nasal bone

Zygomatic bone

Maxilla

MandibleMental foramenMandibular notchMandibular ramus

Coronoid process

Photograph of right side of skull

OccipitomastoidsutureExternal acousticmeatus

Sphenoid bone(greater wing)

Alveolarprocesses

Figure 7.5c Bones of the lateral aspect of the skull, external and internal views.

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Parietal bone

Coronal sutureFrontal bone

Sphenoid bone

Frontal sinusCrista galliNasal boneSphenoidal sinusEthmoid bone(perpendicular plate)

Vomer

MaxillaIncisive canal

Alveolar processes

Mandible

Palatine process of maxilla

Pterygoidprocess ofsphenoid boneMandibularforamenPalatine bone

OccipitomastoidsutureExternal occipitalprotuberanceInternal acousticmeatusSella turcicaof sphenoidbone

Squamoussuture

Lambdoidsuture

Temporalbone

Occipitalbone

GreaterwingLesserwing

Midsagittal section showing the internal anatomy of the left half of skull

Figure 7.5d Bones of the lateral aspect of the skull, external and internal views.

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Greater wing ofsphenoid boneLesser wing ofsphenoid bone

Frontal sinusCrista galli

Ethmoid bone(perpendicular plate)

Palatine bone

Petrous partof temporalbone

External occipitalprotuberanceInternal acousticmeatusSella turcica andsphenoidal sinus

Photo of skull cut through the midline, same view as in (c)

Cranium (cont.)• Occipital bone

• Forms most of skull’s posterior wall and posterior cranial fossa• Articulates with parietal, temporal, and sphenoid bones• Foramen magnum: “large hole” through which brain connects with spinal

cord• Flanked by pair of occipital condyles that articulate with 1st vertebra

• Hypoglossal canal allows cranial nerve XII to pass through

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Cranium (cont.)• External occipital protuberance: protrusion just superior to foramen magnum• External occipital crest: ridges that are site of attachment for ligamentum

nuchae • Superior and inferior nuchal lines: site of attachment for many neck and back

muscles

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Figure 7.4b Anterior and posterior views of the skull.

© 2017 Pearson Education, Inc.Posterior view

Parietal bone Sagittal suture

Occipital bone

Suturalbone

Lambdoidsuture

Superior nuchallineExternaloccipitalprotuberanceOccipitomastoidsuture External

occipital crestOccipitalcondyle

Inferiornuchalline

Mastoidprocess oftemporalbone

Figure 7.6a Inferior aspect of the skull, mandible removed.

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Incisive fossa

Median palatine sutureIntermaxillary suture

Infraorbital foramenMaxilla

Foramen ovale

Foramen lacerumCarotid canalExternal acoustic meatus

Jugular foramen

Foramen magnum

Occipital condyleInferior nuchal lineSuperior nuchal lineOccipital bone

Styloid process

External occipital crest

Inferior view of the skull (mandible removed)

Mastoid process

Parietal bone

Foramen spinosum

External occipitalprotuberance

Zygomatic bone Sphenoid bone(greater wing)

Temporal bone(petrous part)

Mandibularfossa

Temporal bone(zygomatic process)

Maxilla(palatine process)Palatine bone(horizontal plate)

Hardpalate

Stylomastoidforamen

Vomer

Basilar part of theoccipital bone

Figure 7.6b Inferior aspect of the skull, mandible removed.

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Hard palate

Zygomaticarch

Foramen lacerum

Carotid canal

Styloid process

Jugular foramen

Occipital condyle

Foramen magnum

Foramen spinosumMandibularfossa

Mastoidprocess

Foramen ovale

Superior nuchalline

Photo of inferior view of the skull

Cranium (cont.)• Temporal bones: paired bones that make up inferolateral aspects of

skull and parts of cranial base• Three major regions:

1. Squamous: zygomatic processes articulate with zygomatic bone to form zygomatic arch and mandibular fossa makes up part of temporomandibular joint

2. Tympanic: surround external acoustic meatus (external ear canal)

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Cranium (cont.)3. Petrous: houses middle and internal ear cavities

• Makes up part of the middle cranial fossa• Several foramina penetrate petrous region:

• Jugular foramen allows passage of three cranial nerves• Carotid canal: passageway for internal carotid artery• Foramen lacerum: jagged opening covered by cartilage in living human• Internal acoustic meatus and styloidmastoid foramen: cranial nerve passageways

• Mastoid and styloid processes: areas for attachment of several neck and tongue muscles

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Figure 7.5a Bones of the lateral aspect of the skull, external and internal views.

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Coronal suture

Lambdoid suture

Occipital bone

Occipitomastoid suture

External acoustic meatusMastoid processStyloid process

Zygomatic process

Squamous suture

Condylar processMandibular notchMandibular ramus

Mandibular angle Coronoid process

Ethmoid boneLacrimal bone

Lacrimal fossa

Nasal bone

Maxilla

Alveolar processes

MandibleMental foramen

Parietal bone

Temporal bone

External anatomy of the right sideof the skull

Frontal bone

Zygomatic bone

Sphenoid bone(greater wing)

Figure 7.5b Bones of the lateral aspect of the skull, external and internal views.

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Condylar process

Coronal suture

Parietal bone

Lambdoid suture

Squamous suture

Occipital bone

Mastoid processStyloid process

Mandibular angle

Zygomatic processTemporal bone

Frontal bone

Ethmoid boneLacrimal bone

Lacrimal fossa

Nasal bone

Zygomatic bone

Maxilla

MandibleMental foramenMandibular notchMandibular ramus

Coronoid process

Photograph of right side of skull

OccipitomastoidsutureExternal acousticmeatus

Sphenoid bone(greater wing)

Alveolarprocesses

Figure 7.8 The temporal bone.

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Squamouspart

External acousticmeatus

Petrouspart Mastoid process

Styloid processTympanicpart

Mandibularfossa

Zygomaticprocess

Figure 7.6a Inferior aspect of the skull, mandible removed.

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Incisive fossa

Median palatine sutureIntermaxillary suture

Infraorbital foramenMaxilla

Foramen ovale

Foramen lacerumCarotid canalExternal acoustic meatus

Jugular foramen

Foramen magnum

Occipital condyleInferior nuchal lineSuperior nuchal lineOccipital bone

Styloid process

External occipital crest

Inferior view of the skull (mandible removed)

Mastoid process

Parietal bone

Foramen spinosum

External occipitalprotuberance

Zygomatic bone Sphenoid bone(greater wing)

Temporal bone(petrous part)

Mandibularfossa

Temporal bone(zygomatic process)

Maxilla(palatine process)Palatine bone(horizontal plate)

Hardpalate

Stylomastoidforamen

Vomer

Basilar part of theoccipital bone

Figure 7.7a The base of the cranial cavity.

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Cribriform foraminaLesser wingSphenoid

Anterior cranial fossa

Occipital bone

Superior view of the skull, calvaria removed

Greater wing

ViewCrista galli

Optic canal

Foramen rotundumForamen ovaleForamen spinosum

Jugular foramen

Hypoglossal canal

Foramen lacerumInternal acoustic meatus

Hypophyseal fossaof sella turcica

Middle cranialfossaTemporal bone(petrous part)

Posteriorcranial fossa

Frontal boneEthmoidbone

Parietal bone

Foramen magnum

Cribriform plate

Clinical – Homeostatic Imbalance 7.1• Mastoid process contains cavities (sinuses) called mastoid air cells• Mastoiditis can develop if a middle ear infection spreads into mastoid

process area• Mastoid air cells are separated from brain by a very thin bony plate,

increasing chances that the infection could spread to brain

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Cranium (cont.)• Sphenoid bone: complex, bat-shaped bone

• Keystone bone that articulates with all other cranial bones• Sphenoidal sinuses found within body of sphenoid• Body also includes sella turcica prominence that includes hypophyseal fossa

area enclosing the pituitary gland

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