131, 7 Axial Skeleton

8/8/2019 131, 7 Axial Skeleton

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Axial Skeleton Chapter 7

IB 131

Lecturer: Tom Carlson

The Skeleton

Consists of:Bones, cartilage, joints, and ligaments

Composed of 206 named bonesgrouped into two divisions

Axial skeleton (80 bones)Appendicular skeleton (126 bones)

The Axial

Skeleton(in green)

Formed from80 named

bones

Consists ofskull, vertebral

column, and

bony thorax

Figure 7.1a

Skull

Thoracic cage(ribs andsternum)

(a) Anterior view

Facial bonesCranium

Sacrum

Vertebralcolumn

ClavicleScapulaSternumRibHumerusVertebraRadiusUlna

Carpals

PhalangesMetacarpalsFemurPatella

TibiaFibula

TarsalsMetatarsalsPhalanges

The

Axial

Skeleton(in green)

Figure 7.1b

(b) Posterior view

Cranium

Clavicle

Bones ofpectoralgirdle

Bones ofpelvic girdle

Upperlimb

Scapula

RibHumerusVertebraRadiusUlna

CarpalsPhalangesMetacarpalsFemur

Lowerlimb

TibiaFibula

Figure 7.6a

The Skull Formed by cranial and facial bones

Parietal bone

Squamous partof frontal boneNasal bone

Sphenoid bone(greater wing)

Temporal bone

Ethmoid boneLacrimal bone

Zygomatic bone

Maxilla

Mandible

Infraorbital foramen

Mentalforamen

(a) Anterior view of skull

Mentalprotuberance

Frontal bone

Glabella

Frontonasal suture

Supraorbital foramen(notch)

Supraorbital margin

Superior orbital fissure

Inferior orbital fissure

Middle nasal concha

Inferior nasal concha

Vomer

Optic canal

Perpendicular plateEthmoidbone

The CraniumBones of cranium (cranial vault)

Lambdoid

sutureFacial

bones

Squamous

suture

(a) Cranial and facial divisions of the skull

Coronal

suture

Figure 7.2a


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The Cranium

Is the bodys most complex bonystructure

Formed by cranial and facial bones The cranium

Encloses and protects brainProvides attachment for head and neck

muscles

The Face

Facial bones serve toForm framework of the faceForm cavities for the sense organs of sight,

taste, and smell

Provide openings for the passage of airand food

Hold the teeth in placeAnchor muscles of the face

Anterior cranialfossa

Middle cranialfossa

Posterior cranialfossa

(b) Superior view of the cranial fossae

Frontal lobeof cerebrum

Temporal lobeof cerebrum

Cerebellum

Posterior

Middle

Anterior

Cranial

fossae

(c) Lateral view of cranial fossae showing the containedbrain regions

Overview of Skull Geography

Facial bones form anterior aspect Cranium is divided into cranial vault and the

base

Internally, prominent bony ridges divide skullinto distinct fossae

Figure 7.2b, c

Anterior cranialfossa

Middle cranialfossa

Posterior cranialfossa

(b) Superior view of the cranial fossae

Frontal lobeof cerebrum

Temporal lobeof cerebrum

Cerebellum

Posterior

Middle

Anterior

Cranial

fossae

(c) Lateral view of cranial fossae showing the containedbrain regions

Cranial Fossae

Anterior cranial fossa Middle cranial fossa Posterior cranial fossa

Figure 7.2b, c

Small Cavities of Skull

The skull contains smaller cavitiesMiddle and inner ear cavitiesin lateral

aspect of cranial base

Nasal cavitylies in and posterior to thenose

Orbitshouse the eyeballsAir-filled sinusesoccur in several bones

around the nasal cavity

Overview of Skull Geography

The skull contains approximately 85named openings

Foramina, canals, and fissuresProvide openings for important structures

Spinal cord Blood vessels serving the brain 12 pairs of cranial nerves


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Cranial Bones

Formed from eight large bonesPaired bones include

Temporal bonesParietal bones

Unpaired bones includeFrontal boneOccipital boneSphenoid boneEthmoid bone

Figure 7.6a

The Skull Formed by cranial and facial bones

Parietal bone



Temporal bone

Ethmoid bone

Lacrimal bone

Zygomatic bone

Maxilla

Mandible


Mentalforamen


Mentalprotuberance

Frontal bone

Glabella

Frontonasal suture


Supraorbital margin



Middle nasal concha


Vomer

Optic canal


Major cavities of skull Lateral aspect of skull

Lateral aspect of skullThe Cranium

Bones of cranium (cranial vault)

Lambdoid

sutureFacial

bones

Squamous

suture

(a) Cranial and facial divisions of the skull

Coronal

suture

Figure 7.2a


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Parietal Bones and Sutures

Parietal bones form superior and lateralparts of skull

Four sutures of the craniumCoronal sutureruns in the coronal plane

Located where parietal bones meet the frontalbone

Squamous sutureoccurs where eachparietal bone meets a temporal boneinferiorly

Lambdoidsuture

Occipital bone

Superior nuchal line

External occipital

protuberance

Sutural bone

Inferior nuchal line

Occipitalcondyle

External occipital crestOccipitomastoidsuture

Parietal bone

Sagittal suture

The Skull Posterior View

Figure 7.5

Parietal Bones and Sutures

Four sutures of the cranium (continued)Sagittal sutureoccurs where right and

left parietal bones meet superiorly

Lambdoid sutureoccurs where theparietal bones meet the occipital boneposteriorly

Sutural Bones

Small bones that occur within sutures Irregular in shape, size, and location Not all people have sutural bones

Lambdoidsuture

Occipital bone


External occipitalprotuberance

Sutural bone


Occipitalcondyle


Parietal bone

Sagittal suture


Figure 7.5

Frontal Bone

Forms the forehead and roofs of orbits Supraorbital marginsuperior margin

of orbits

Glabellasmooth part of frontal bonebetween superciliary (eyebrow) arches

Frontal sinuses within frontal bone Contributes to anterior cranial fossa


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Figure 7.6a

Cranial & Facial Bones of Skull

Parietal bone



Temporal bone

Ethmoid bone

Lacrimal bone

Zygomatic bone

Maxilla

Mandible


Mentalforamen


Mentalprotuberance

Frontal bone

Glabella

Frontonasal suture


Supraorbital margin



Middle nasal concha


Vomer

Optic canal


Cranial and Facial Bones of Skull

Occipital Bone

Forms the posterior portion of thecranium and cranial base

Articulates with the temporal bones andparietal bones

Forms the posterior cranial fossa Foramen magnum located at its base

Maxilla

(palatine process)Hard

palate

Zygomatic bone

Incisive fossa

Median palatine sutureIntermaxillary suture

Infraorbital foramenMaxillaSphenoid bone(greater wing)

Foramen ovalePterygoid process

Foramen lacerumCarotid canalExternal acoustic meatusStylomastoid

foramenJugular foramen

Foramen magnum

Occipital condyle



Temporal bone

(zygomatic process)

Mandibular fossa

Vomer

Styloid process

External occipital crestExternal occipitalprotuberance(a) Inferior view of the skull (mandible removed)

Mastoid processTemporal bone(petrous part)

Basilar part ofthe occipital boneOccipital bone

Palatine bone

(horizontal plate)

Foramen spinosum

Inferior Aspect of the Skull

Figure 7.7a

Inferior Aspect of Skull

(b) Photograph of right side of skull

Sphenoid bone

(greater wing)Coronal suture

Parietal bone

Squamous suture

Zygomatic process

Temporal bone

Lambdoid sutureOccipital bone

External occipitalprotuberanceOccipitomastoidsutureExternal acousticmeatusMastoid process Styloid

processMandibular ramusMandibular angle

Mental foramen

Frontal bone


Nasal bone

Lacrimal fossaZygomatic

bone

Maxilla

Mandible

Coronoidprocess

Alveolarmargins

Mandibularcondyle

Mandibular

notch

Lateral Aspect of the Skull

Figure 7.4b


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Lambdoidsuture

Occipital bone


External occipital

protuberance

Sutural bone


Occipitalcondyle


Parietal bone

Sagittal suture


Figure 7.5

Occipital Bone

Features and structuresOccipital condylesHypoglossal foramenExternal occipital protuberanceSuperior nuchal linesInferior nuchal lines

Temporal Bones

Lie inferior to parietal bones Form the inferolateral portion of the

skull

Term temporal comes from Latin wordfor time

Specific regions of temporal boneSquamous, temporal, petrous, and mastoid

regions

Lateral aspect of skull

(b) Photograph of right side of skull

Sphenoid bone

(greater wing)Coronal suture

Parietal bone

Squamous suture

Zygomatic process

Temporal bone

Lambdoid sutureOccipital bone

External occipitalprotuberanceOccipitomastoidsutureExternal acousticmeatusMastoid process Styloid

processMandibular ramusMandibular angle

Mental foramen

Frontal bone


Nasal bone

Lacrimal fossaZygomatic

bone

Maxilla

Mandible

Coronoidprocess

Alveolarmargins

Mandibularcondyle

Mandibular

notch

Lateral Aspect of the Skull

Figure 7.4b

The Temporal Bone

Figure 7.8

Mastoid

region

External acoustic

meatus

Mastoid process

Styloid process Tympanicregion

Mandibularfossa

Zygomatic

process

Squamous

region


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The Temporal Bone The mastoid process

Site for neck muscle attachmentContains air sinuses

Petrous region (Fig 7.9)Projects medially, contributes to cranial baseAppears as a boney wedge between

occipetal bone posteriorly and sphenoid

bone anteriorly

Houses cavities of middle and internal ear Contributes to the middle and posterior cranial

fossae

Cranial cavity floor

Cranial cavity floorThe Temporal Bone

Foramina of the temporal bone (Fig 7.9)Jugular foramen

At boundary with occipital boneCarotid canalFormane lacerumInternal accoustic meatus

The Sphenoid Bone

Spans the width of the cranial floor Resembles a butterfly or bat Has of a body Has three pairs of processes Contains five important openings Is the keystone of the cranium

The Sphenoid Bone

Body

The superior part of the body bears asaddle-shaped prominence called a

sella turcica

The seat of this saddle holds thehypophyseal fossa , holds the the

pituitary gland (= hypophysis)


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The Sphenoid Bone

Processes (Fig 7.10)

Greater wings Lesser wings Pterygoid processes

(a) Superior view, as in Figure 7.9

Optic

canal

Greater

wingSellaturcica

Lesser wing

Foramen rotundumForamen ovale

Foramen spinosumBody of sphenoid

The Sphenoid Bone

Figure 7.10a

Greaterwing

Body of sphenoid

Superiororbital

fissure

Lesserwing

Pterygoidprocess

(b) Posterior view

The Sphenoid Bone

Figure 7.10b

The Sphenoid Bone

Openings (Figs 7.9, 7.10)

Optic canal: lies just anterior to sella tursica Superior orbital fissure: long slit between greater

and lesser wings

Foramen rotundum: in medial part of greaterwing

Foramen ovale: posteriolateral to foramenrotundum

Foramen spinosum: posteriolateral to foramenovale

Cranial cavity floor Lateral aspect of skull


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Figure 7.6a


Parietal bone



Temporal bone

Ethmoid bone

Lacrimal bone

Zygomatic bone

Maxilla

Mandible


Mentalforamen


Mentalprotuberance

Frontal bone

Glabella

Frontonasal suture


Supraorbital margin



Middle nasal concha


Vomer

Optic canal


The Ethmoid Bone

Lies between nasal and sphenoidbones

Forms most of the medial bony regionbetween the nasal cavity and orbits

Lateral aspect of skull

Figure 7.6a


Parietal bone



Temporal bone

Ethmoid bone

Lacrimal bone

Zygomatic bone

Maxilla

Mandible


Mentalforamen


Mentalprotuberance

Frontal bone

Glabella

Frontonasal suture


Supraorbital margin



Middle nasal concha


Vomer

Optic canal


Midsagittal section through skull Midsagittal section through skull


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Orbitalplate

Ethmoidalair cells

Perpendicularplate

Middlenasal concha

Cribriformplate

Olfactoryforamina

Crista galli

Leftlateralmass

Figure 7.12

The Ethmoid Bone The Ethmoid Bone

Cribiform platesuperior surface of theethmoid bone

Contain olfactory foramina Crista galliattachment for falx cerebri;

falx cerebri is large vertical sheet which

lies in between cerebral hemispheres

Perpendicular plateforms superiorpart of nasal septum

The Ethmoid Bone

Lateral massescontain air cells Superiorand middle nasal conchae

Extend medially from lateral masses

Bones of Nasal Cavity

Bones of Nasal Cavity Facial Bones

Unpaired bonesMandible and vomer

Paired bonesMaxillaeZygomatic bonesNasal bonesLacrimal bonesPalatine bonesInferior nasal conchae


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Parietal bone

Squamous partof frontal boneNasal boneSphenoid bone

(greater wing)Temporal boneEthmoid boneLacrimal boneZygomatic bone

Maxilla

Mandible


Mental

foramen


Mental

protuberance

Frontal bone

Glabella

Frontonasal suture

Supraorbital foramen

(notch)Supraorbital marginSuperior orbital fissure


Middle nasal concha


Vomer

Optic canal


Facial Bones

Figure 7.6a

Mandible

The lower jawbone is the largest andstrongest facial bone

Composed of two main partsHorizontal bodyTwo upright rami

Coronoid

process

Mandibular foramen

Mental

foramen

Mandibular

angle

Ramus

ofmandible

Mandibular

condyle

Mandibular notch

Mandibular fossa

of temporal bone

Body of mandible

Alveolar

margin

(a) Mandible, right lateral view

Temporomandibular

joint

Mandible

Figure 7.13a

Maxillary Bones

Articulate with all other facial bonesexcept the mandible

Contain maxillary sinuseslargestparanasal sinuses

Forms part of the inferior orbital fissure Are the keystone bones of the face

Maxillary Bones

Figure 7.13b

Frontal process

Articulates withfrontal bone

Anterior nasalspine

Infraorbitalforamen

Alveolarmargin

(b) Maxilla, right lateral view

Orbital surface

Zygomaticprocess

(cut)

Maxilla

(palatine process)Hardpalate

Zygomatic bone

Incisive fossa



Foramen ovalePterygoid process



Foramen magnum

Occipital condyle



Temporal bone

(zygomatic process)

Mandibular fossa

Vomer

Styloid process

External occipital crestExternal occipital

protuberance

(a) Inferior view of the skull (mandible removed)



Palatine bone

(horizontal plate)

Foramen spinosum

Maxillary Bones

Figure 7.7a


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Other Bones of the Face

Zygomatic bonesForm lateral wall of orbits

Nasal bonesForm bridge of nose

Lacrimal bonesLocated in the medial orbital walls

Palatine bonesComplete the posterior part of the hard

palate

Nasal Cavity

Figure 7.14a

Frontal sinus

Superiornasal conchaMiddle

nasal concha

Ethmoidbone


Nasal bone

Maxillary bone(palatine process)

Palatine bone(perpendicularplate)

Palatine bone(horizontal plate)

Pterygoidprocess

(a) Bones forming the left lateral wall of the nasal cavity(nasal septum removed)

Sphenoidsinus

Sphenoidbone

Superior, middle, andinferior meatus

Anterior nasal spine

Other Bones of the Face

VomerForms the inferior part of the nasal septum

Inferior nasal conchaeThin, curved bones that project medially

form the lateral walls of the nasal cavity

Maxilla

(palatine process)Hard

palate

Zygomatic bone

Incisive fossa



Foramen ovale

Pterygoid process



Foramen magnum

Occipital condyle



Temporal bone

(zygomatic process)

Mandibular fossa

Vomer

Styloid process

External occipital crestExternal occipitalprotuberance(a) Inferior view of the skull (mandible removed)



Palatine bone

(horizontal plate)

Foramen spinosum

Maxillary Bones

Figure 7.7a

Special Parts of the Skull

Orbits Nasal cavity Paranasal sinuses Hyoid bone

Vomer

Crista galliCribriformplate

Ethmoidbone Frontal sinus

Nasal bone

Septalcartilage

Alveolar marginof maxilla

Perpendicular

plate of

ethmoid bone

Sella turcica

Sphenoid sinus

Palatine bone

Palatine processof maxilla

(b) Nasal cavity with septum in place showing the contributions of theethmoid bone, the vomer, and septal cartilage

Hardpalate

Nasal Septum

Figure 7.14b


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Paranasal Sinuses

Air-filled sinuses are located withinFrontal boneEthmoid boneSphenoid boneMaxillary bones

Lined with mucous membrane Lighten the skull

Paranasal Sinuses

Figure 7.15a, b

Frontalsinus

Ethmoidalair cells(sinus)

Maxillarysinus

Sphenoid

sinus

(a) Anterior aspect

FrontalsinusEthmoidalair cells

Maxillarysinus

Sphenoidsinus

(b) Medial aspect

Orbit walls

Roof Lateral wall Medial wall Floor

Orbit

Orbit walls formed by parts of

seven bones

Frontal Sphenoid Zygomatic Maxillary Palatine Lacrimal Ethmoid

Orbits


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Orbit wall openings

Superior orbital fissures Inferior orbital fissures Optic canals Lacrimal fossa

Figure 7.17

The Hyoid Bone Associated with skull

but not directly incontact with any other

bone

Lies inferior to themandible in anterior

neck

The only bone with nodirect articulation with

any other bone

Acts as a movablebase for the tongue

Greater horn

Lesser horn

Body

The Vertebral Column

Formed from 26 bones in the adult Transmits weight of trunk to the lower

limbs

Surrounds and protects the spinal cord


Serves as attachment sites for musclesof the neck and back

Held in place by ligamentsAnterior and posterior longitudinal

ligaments

Ligamentum flavum

Posterior longitudinalligament

Anterior longitudinalligament

Body of a vertebra

Intervertebral disc

(b) Anterior view of part of the spinal column

Ligaments of the Spine

Supraspinous ligamentIntervertebraldisc

Anteriorlongitudinalligament

Intervertebral foramen


Anulus fibrosus

Nucleus pulposus

Sectioned body

of vertebra

Transverse process

Sectioned

spinous process

Ligamentum flavum

Interspinous

ligament

Inferior articular process

(a) Median section of three vertebrae, illustrating the composition

of the discs and the ligaments

Figure 7.19a, b


Figure 7.18

Cervical curvature(concave)

7 vertebrae, C1 C7

Thoraciccurvature

(convex)12 vertebrae,

T1 T12

Lumbarcurvature

(concave)5 vertebrae, L1 L5

Sacralcurvature

(convex) 5 fusedvertebrae sacrum

Coccyx4 fused vertebraeAnterior view Right lateral view

C1

T123456789101112

L1234

5

234567

SpinousprocessTransverseprocesses

IntervertebraldiscsIntervertebralforamen


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Regions and Normal

Curvatures

The Vertebral column has five majorregions7 cervical vertebrae of the neck region12 thoracic vertebrae5 lumbar vertebraeSacrumfive fused bonesCoccyxinferior to sacrum

Regions and Normal

Curvatures

Curvatures of the spineCervical and lumbar curvatures

Concave posteriorlyThoracic and sacral curvatures

Convexposteriority


Figure 7.18

Cervical curvature(concave)

7 vertebrae, C1 C7

Thoraciccurvature

(convex)12 vertebrae,

T1 T12

Lumbarcurvature

(concave)5 vertebrae, L1 L5

Sacralcurvature

(convex) 5 fusedvertebrae sacrum

Coccyx4 fused vertebraeAnterior view Right lateral view

C1

T123456789101112

L1234

5

234567

SpinousprocessTransverseprocesses

Intervertebraldiscs

Intervertebralforamen

Regions and Normal

Curvatures

Curvatures increase resilience of spine Thoracic and sacral curvatures

Primary curvatures Present at birth

Lumbar curvatureDevelops when baby begins to walk


Major supporting ligamentsAnterior longitudinal ligament

Attaches to bony vertebrae andintervertebral discs

Prevents hyperextensionPosterior longitudinal ligament

Narrow and relatively weakAttaches to intervertebral discs



Body of a vertebra

Intervertebral disc







Anulus fibrosus

Nucleus pulposus

Sectioned body

of vertebra

Transverse process

Sectioned

spinous process

Ligamentum flavum

Interspinous

ligament




Figure 7.19a, b


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Intervertebral Discs

Cushion-like pads between vertebraeComposed of

Nucleus pulposusAnulus fibrosus

Intervertebral Discs

Nucleus pulposusGelatinous inner sphereAbsorbs compressive stresses

Anulus fibrosusOuter fings formed of ligamentInner rings formed of fibrocartilageContain the nucleus pulposus

Intervertebral Discs of Spine

Herniated Intervertebral Disc

Figure 7.19c, d

Vertebral spinous process(posterior aspect of vertebra)

Spinal nerve root

Anulus fibrosusof disc

Herniated portionof disc

Nucleuspulposusof disc

Spinal cord

(c) Superior view of a herniated intervertebral disc

Transverseprocess

(d) MRI of lumbar region of vertebral column in sagittalsection showing normal and herniated discs

Nucleus pulposusof intact disc

Herniated nucleuspulposus

General Structure of Vertebrae

PLAY Spine (horizontal)

Figure 7.20

Posterior

Anterior

Lamina

Superiorarticularprocessandfacet

Transverse

process

Pedicle

Spinous

process

Vertebral

arch

Vertebral

foramen

Body

(centrum)

General Structure of

Vertebrae

Common structures to all regionsBodyVertebral archVertebral foramenSpinous processTransverse processSuperior and inferior articular processesIntervertebral foramina



Body of a vertebra

Intervertebral disc







Anulus fibrosus

Nucleus pulposus

Sectioned body

of vertebra

Transverse process

Sectioned

spinous process

Ligamentum flavum

Interspinous

ligament




Figure 7.19a, b


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Regions Vertebral

Characteristics

Specific regions of the spine performspecific functions

Types of movement that may occurbetween vertebrae

Flexion and extensionLateral flexionRotation in the long axis

Cervical Vertebrae

Seven cervical vertebrae (C1 C7)are the lightest vertebrae in thespine

Dens of axis

Transverse ligament

of atlasC1 (atlas)

C2 (axis)

C3

Bifid spinous

process

Transverse processes

C7 (vertebra

prominens)

(a) Cervical vertebrae

Inferior articular

process

Cervical Vertebrae

Figure 7.22a

Cervical Vertebrae

Table 7.2a

The Atlas

C1 is termed the atlas Lacks a body and spinous process Supports the skull

Superior articular facets receive theoccipital condyles

Allows flexion and extension of neckNodding the head yes

The Atlas

Figure 7.21a

Anterior arch

Superior articular

facet

Transverse

foramen

Posterior arch

Posterior tubercle

Anterior tubercle

Posterior

Lateral

masses

(a) Superior view of atlas (C1)

C1


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Lambdoidsuture

Occipital bone


External occipital

protuberance

Sutural bone


Occipitalcondyle


Parietal bone

Sagittal suture


Figure 7.5

The Atlas

Figure 7.21b

Facet for dens

Transverse

process Lateral

masses

Transverse foramen

Posteriorarch Posterior tubercle

Posterior

Anterior tubercle

Anteriorarch

(b) Inferior view of atlas (C1)

Inferior

articular

facet

C1

The Axis

Has a body and spinous process Dens (odontoid process) projects superiorly

Formed from fusion of the body of the atlas withthe axis

Acts as a pivot for rotation of the atlas and skullParticipates in rotating the head from side to

side

The Axis

Figure 7.21c

C2Posterior

Dens

(c) Superior view of axis (C2)

Inferior

articularprocess

Body

Superior

articularfacet

Transverse

process

Pedicle

Lamina

Spinous process

Dens of axis

Transverse ligamentof atlasC1 (atlas)

C2 (axis)

C3

Bifid spinousprocess

Transverse processes

C7 (vertebraprominens)

(a) Cervical vertebrae

Inferior articular

process

Cervical Vertebrae

Figure 7.22a

Cervical Vertebrae C3 C7 Body: small and wide laterally (side to side) Spinous process: short and bifid (except C7) and

project posteriorally

Vertebral foramen: triangular and large Transverse processes contain foramina Superior facets directed superposteriorly Inferior facets directed inferoanteriorly Spine region with the greatest range of motion

with the following movement allowed: flexion &

extension, lateral flexion, rotation


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Cervical, Thoracic, & Lumbar Vertebrae

Superior View


Right Lateral View

Cervical, Thoracic, & Lumbar VertebraeThoracic vertebrae

Thoracic Vertebrae

All articulate with ribs Body: larger than cervical bodies and heart-

shaped from superior view

Spinous processes are long and pointinferiorly

Vertebral foramen are circular

Costal Facets of Thoracic Vertebrae

which interface with ribs

Inferior costal facet for head of rib Superior costal facet for head of rib Transverse costal facet for tubercle of rib (except

for T11 T12)

Each of these above three facets are present onboth sides of vertebrae, so each vertebrae has a

total of six facets which interface with ribs

Usually, the head of a rib is attached to the bodiesof two vertebrae, the inferior costal facet of the

superior vertebra and the superior costal facet of

the inferior vertebra


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Right Lateral View Ribs

Figure 7.25a, b

Junction withcostal cartilage

ShaftHead Neck

Articular faceton tubercle

Costal angleCostal groove

Facets for articulationwith vertebrae

(a) A typical rib (rib 6, right), posterior view

Transverse costal facet(for tubercle of rib)

Superior costal facet(for head of rib)

Body of vertebra

Head of rib

Intervertebral disc

Tubercle of rib

Neck of rib

Shaft Sternum

Angleof rib

Cross-sectionof rib Costal groove

(b) Vertebral and sternal articulations of a typical true rib

Costal cartilage

Spinous process

Articular faceton tubercle of rib

Shaft

Ligaments

Neck of rib

Head of rib Body of

thoracic

vertebra

Transverse

costal facet

(for tubercleof rib)

Superior costal facet

(for head of rib)

(c) Superior view of the articulation between a rib and athoracic vertebra

Ribs

Figure 7.25c

Connections between Thoracic

Vertebral Bodies

Laterally each side of the vertebral bodybears two facets (demifacets), one at the

superior edge and one at the inferior edge

These demifacets interface with vertebralbodies above and below

Superior articular facets point posteriorly Inferior articular processes point anteriorly Allows rotation and limits flexion and

extension

Thoracic vertebraeThoracic Vertebrae

Table 7.2b


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Superior View


Right Lateral View

The Thoracic Cage

Forms the framework of the chest Components

Thoracic vertebraeposteriorlyRibslaterallySternum and costal cartilageanteriorly

Protects thoracic organs Supports shoulder girdle and upper limbs Provides attachment sites for muscles Intercostalspaces

True

ribs

(17

False

ribs(812)

Jugular notchClavicular notch

Manubrium

Sternal angleBody

Xiphisternal

jointXiphoid

process

L1

VertebraFloating ribs (11, 12)

(a) Skeleton of the thoracic cage, anterior view

Sternum

Costal cartilageCostal margin

The Thoracic Cage

Figure 7.24a

The Thoracic Cage

Figure 7.24b

XiphisternalXiphisternaljoint

Heart

Sternal angle

Jugular notch

(b) Midsagittal section through the thorax, showingthe relationship of surface anatomical landmarks

of the thorax to the vertebral column

T2

T4

T3

T9

Sternum

Formed from three sectionsManubriumsuperior section

Articulates with medial end of claviclesBodybulk of sternum

Sides are notched at articulations forcostal cartilage of ribs 27

Xiphoid processinferior end of sternum Ossifies around age 40


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Intercostal

spaces

Trueribs

(17

False

ribs

(812)


Manubrium

Sternal angleBodyXiphisternal

jointXiphoidprocess

L1Vertebra

Floating ribs (11, 12)(a) Skeleton of the thoracic cage, anterior view

Sternum


The Thoracic Cage

Figure 7.24a

Sternum

Anatomical landmarksJugular notch

Central indentation at superior border ofthe manubrium

Sternal angle A horizontal ridge where the manubriumjoins the body

Xiphisternal joint Where sternal body and xiphoid process

fuse

Lies at the level of the 9th thoracicvertebra

Ribs

All ribs attach to vertebral column posteriorlyRib pairs 1-7 (vertebrosternal ribs) - superior

seven pairs of ribs which attach to sternum by

costal cartilage

Rib pairs 8-10, (vertebrochondral ribs) pairsof ribs which attach to the sternum indirectly

Ribs pairs 1112 (floating ribs) are notattached to the sternum

Ribs 8-12 are sometimes called false ribsbecause they attach to the sternum indirectly

(ribs 8-10) or not at all (ribs 11-12)

Intercostal

spaces

True

ribs

(17

False

ribs(812)


Manubrium

Sternal angleBody

Xiphisternal

jointXiphoid

process

L1

VertebraFloating ribs (11, 12)

(a) Skeleton of the thoracic cage, anterior view

Sternum


The Thoracic Cage

Figure 7.24a

Ribs

Figure 7.25a, b

Junction withcostal cartilage

ShaftHead Neck

Articular faceton tubercle

Costal angleCostal groove

Facets for articulationwith vertebrae

(a) A typical rib (rib 6, right), posterior view

Transverse costal facet(for tubercle of rib)

Superior costal facet(for head of rib)

Body of vertebra

Head of rib

Intervertebral disc

Tubercle of rib

Neck of rib

Shaft Sternum

Angleof rib

Cross-sectionof rib Costal groove

(b) Vertebral and sternal articulations of a typical true rib

Costal cartilage

Spinous process

Articular facet

on tubercle of rib

Shaft

Ligaments

Neck of rib

Head of rib Body of

thoracic

vertebra

Transverse

costal facet

(for tubercleof rib)

Superior costal facet

(for head of rib)

(c) Superior view of the articulation between a rib and a

thoracic vertebra

Ribs

Figure 7.25c


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Superior

articularprocess

Transverse

process

Spinous

process

Intervertebral

disc

Body

Inferior

articular

process

(c) Lumbar vertebrae

Lumbar Vertebrae

Figure 7.22c

Lumbar Vertebrae (L1L5) Bodies are thick and robust Transverse processes are thin and tapered Spinous processes are thick, blunt, and point

posteriorly

Vertebral foramina are triangular Superior articular facets face posteromedially or

medially

Inferior articular facets face anterolaterally orlaterally

Allows flexion and extensionrotation prevented

Lumbar Vertebrae

Table 7.2c


Superior View


Right Lateral ViewSacrum (S1S5)

Shapes the posterior wall of pelvis Formed from 5 fused vertebrae Superior surface articulates with L5 Inferiorly articulates with coccyx


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Sacrum (S1S5) Anterior View

Sacral promontory: Where theanterosuperior margin of the first sacralvertebrae bulges into pelvic cavity

Human bodys center of gravity is 1 cmposterior to sacral promontory

Four transverse ridges cross the anteriorsurface of the sacrum, marking the lines offusion of sacral vertebrae

The anterior sacral foramina transmit theventral divisions (ventral rami) of the sacralspinal nerves

Sacrum

Figure 7.23

Body offirst

sacralvertebra

Transverseridges (sites

of vertebralfusion)

Coccyx Coccyx

Anteriorsacral

foraminaApexPosteriorsacral

foramina

Mediansacral

crest

Sacral promontorySacral

canal

Sacralhiatus

BodyFacet of superiorarticular process

Lateralsacral

crest

Auricularsurface

Ala

(a) Anterior view (b) Posterior view

Sacrum (S1S5) Posterior View

On the posterior surface in the midline is thebumpy median sacral crest which representsthe fused spinous processes of the sacralvertebrae

Lateral to the medial sacral crest are theposterior sacral foramina which transmit thedorsal rami of the sacral spinal nerves

Just lateral to these is the lateral sacral crest Ala (wing)develops from fused rib elements

Sacrum

Sacral foraminaVentral foramina

Passage for ventral rami of sacral spinalnerves

Dorsal foramina Passage for dorsal rami of sacral spinal

nerves

Sacrum

Figure 7.23

Body offirst

sacralvertebra

Transverseridges (sites

of vertebralfusion)

Coccyx Coccyx

Anteriorsacral

foraminaApexPosteriorsacral

foramina

Mediansacral

crest

Sacral promontorySacralcanal

Sacralhiatus

BodyFacet of superiorarticular process

Lateral

sacralcrest

Auricularsurface

Ala

(a) Anterior view (b) Posterior view

Coccyx

Is the tailbone Formed from 35 fused vertebrae Offers only slight support to pelvic

organs


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Disorders of the Axial

Skeleton

Cleft palateA common congenital disorderRight and left halves of palate fail to fuse

medially

Stenosis of the lumbar spineNarrowing of the vertebral canalCan compress roots of spinal nerves

Cleft palate

Disorders of the Axial

Skeleton

Abnormal spinal curvaturesScoliosisan abnormal lateral curvatureKyphosisan exaggerated thoracic

curvature

Lordosisan accentuated lumbarcurvature; swayback

Abnormal spinal curvatures

The Axial Skeleton Throughout Life

Flat membrane bones begin to ossify insecond month of embryonic

development

Bone tissue grows outward fromossification centers

At birth, skull bones are separated bystill-unossified remnants of membranes

call fontanelles

Fontanelles Fontanelles are unossified remnants of

membranes present at birth

Anterior, posterior, mastoid, and sphenoidalfontanelles

Allows skull to be safely compressed and moldedas infant passes through narrow birth canal

A visible arterial pulse may be seen in thefontanelles

Fontanelles tend to be replaced by bone by theend of the 1st year, however, the anterior

fontanelle may take 1.5 to 2 years to ossify and

close


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Fontanelles

Figure 7.28a

Occipital

bone

Parietal bone

Anteriorfontanelle

Frontal suture

Frontal bone

Ossification

center

(a) Superior view

Posterior fontanelle

Fontanelles

Figure 7.28b

Frontal bone

Sphenoidal

fontanelle

(b) Lateral view

Posterior

fontanelle

Mastoid

fontanelle

Parietal boneOssification

center

Occipital bone

Temporal bone

(squamous

portion)

Bone formation

Many bones of the face and skullcapform by intramembranous ossification

Endochondral bones of the skullOccipital boneSphenoidEthmoid bonesParts of the temporal bone

Skull and face growth

9 months of age: skull adult size 2 years of age: skull adult size 8-9 years: cranium almost adult size 6-13 years: accelerated growth of jaws,

cheekbones, large permanent teeth,

nose, and paranasal sinuses

The Axial Skeleton

Throughout Life

Aging of the axial skeletonWater content of the intervertebral discs

decreases with age

By age 55, loss of a few centimeters inheight is common

Thorax becomes more rigid as costalcartilage gradually ossifies

Bones lose mass with age

Documents

131, 7 Axial Skeleton