head and neck anatomy for dental medicine

Head and Neck Anatomyfor Dental Medicine

Schuenke / SchulteSchum

acherH

ead and Neck Anatomy

for Dental Medicine

Dies ist ein Blindtext ohne Sinn, trotzdem ist er nicht sinnlos. Er zeigt die Textgestaltung auf der U4 mit einer Mindest-Schriftgröße und einem entsprechenden Mindest-Zeilenabstand.

Dies ist immer noch ein Blindtext ohne Sinn, trotzdem ist er nicht sinnlos. Er zeigt die Textgestaltung auf der U4 mit einer Mindest-Schriftgröße und einem entsprechenden Mindest-Zeilenabstand. Dies ist ein Blindtext ohne Sinn, trotzdem ist er nicht sinnlos. Er zeigt die Textgestaltung auf der U4 mit einer Mindest-Schriftgröße und einem entsprechenden Mindest-Zeilenabstand. Schon wieder ein sinnvoller Blindtext.

www.thieme.com

ISBN 978-1-60406-209-0

Michael SchuenkeErik SchulteUdo Schumacher

Consulting EditorEric Baker

Illustrations byMarkus VollKarl Wesker

© 2009 Georg Thieme Verlag KG

Upper lip

Lower lip

Oral fissure Angle ofmouth

Nasolabialcrease

Philtrum

Upper lip

Oralvestibule

Softpalate

Faucialisthmus

Oral cavityproper

Oralvestibule

Lower lip

Frenulum oflower lip

Dorsumof tongue

Palatinetonsil

Palatopharyn-geal arch

Palatoglossalarch

Uvula

Hardpalate

Frenulum ofupper lip

Nasalseptum

Oral cavityproper

Upper lip

Lower lip

Mandible

Mylohyoid

Hyoid bone

Epiglottis

Tongue

Geniohyoid

Uvula

Softpalate

Torustubarius

Hardpalate

A

Superiorlabial

vestibule

B

Airway Foodway

Laryngo-pharynx

Oro-pharynx

Naso-pharynx

Fig. 9.2 Oral cavityAnterior view. The dental arches (with the alveolar processes of the maxilla and mandible) subdivide the oral cavity into two parts:

• Oralvestibule:portionoutsidethedentalarches,boundedononeside by the lips/cheek and on the other by the dental arches.

• Oralcavityproper:regionwithinthedentalarches,boundedposte-riorlybythepalatoglossalarch.

Theoralcavityislinedbyoralmucosa,whichisdividedintolining,mas-ticatory,andgingivalmucosa.Themucosalliningconsistsofnonkera-tinized,stratifiedsquamousepitheliumthatismoistenedbysecretionsfromthesalivaryglands.Thekeratinized,stratifiedsquamousepithe-liumof the skinblendswith thenonkeratinized, stratified squamousepithelium of the oral cavity at the vermilion border of the lip. The mas-ticatory mucosa is orthokeratinized to withstand masticatory stress. Thegingivathatsupportstheteethiskeratinized.

Fig. 9.3 Organization and boundaries of the oral cavityMidsagittal section, left lateralview.Theoralcavity is locatedbelowthe nasal cavity and anterior to the pharynx. The inferior boundary of the oral cavity proper is formed by mylohyoid muscle. The roof of the oral cavity is formed by the hard palate in its anterior two thirds and

Fig. 9.1 Lips and labial creasesAnteriorview.Theupperandlowerlipsmeetattheangleofthemouth.Theoralfissureopensintotheoralcavity.Changesinthelipsnotedonvisual inspectionmay yield importantdiagnostic clues: Blue lips (cy-anosis)suggestadiseaseoftheheart,lung,orboth,anddeepnasola-bialcreasesmayreflectchronicdiseasesofthedigestivetract.

bythesoftpalate(velum)initsposteriorthird.Theuvulahangsfromthe soft palate between the oral cavity and pharynx. The midportion of the pharynx (oropharynx) is the area in which the airway and food-way intersect (B).

178

Regions of the Head 9. Oral Cavity & Perioral Regions

Oral Cavity: Overview

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B

Interalveolar septum

Molars

Premolars

Canine

Incisors

Mental (genial)spines

Angle ofmandible

Coronoidprocess

Head (condyle)of mandible

Pterygoidfovea

A

Incisivesuture

Interalveolarseptum

Incisive fossa

Molars

Premolars

Canine

Incisors

Medianpalatinesuture

Greaterpalatineforamen

Lesserpalatineforamen

Posteriornasal spine

Transversepalatine suture

Fig. 9.4 Maxillary and mandibular archesA Maxilla. Inferior view.B Mandible. Superior view.There are three basic types of teeth — incisiform (incisors), caniniform (canines), and molari-form (premolars and molars) — that perform cutting,piercing,andgrindingactions,respec-tively. Each half of the maxilla and mandible containsthefollowingsetsofteeth:

• Anteriorteeth:twoincisorsandonecaninetooth.

• Posterior(postcanine)teeth:twopremolars and three molars.

Each tooth is given an identification code todescribethespecificlocationofdentallesionssuch as caries (see p. 180).

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3130

29 28 27 26 25

18192021222324

1514

131211109

23

4 5 6 7 8

1 16

32 17

LabialMesial

Palatal

Distal

Buccal Distal

Mesial

Lingual

Labial

Buccal

A B

Fig. 9.5 Coding the permanent teethIntheUnitedStates,thepermanentteetharenumberedsequentially,not assigned to quadrants. Progressing in a clockwise fashion (from theperspectiveoftheviewer),theteethoftheupperarcarenumbered

Fig. 9.6 Designation of tooth surfacesA Inferior view of the maxillary dental arch. B Superior view of the mandibular dental arch. The mesial and distal tooth surfaces are those closesttoandfarthestfromthemidline,respectively.Thetermlabial is

1to16,andthoseofthelowerareconsidered17to32.Note: The third uppermolar(wisdomtooth)onthepatient’srightisconsidered1.

usedforincisorsandcanineteeth,andbuccal is used for premolar and molar teeth. Palataldenotestheinsidesurfaceofmaxillaryteeth,andlingualdenotestheinsidesurfaceofmandibularteeth.Thesedesigna-tions are used to describe the precise location of small carious lesions.

180


Permanent Teeth

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Mandibularcanal

Articulartubercle

Nasalseptum

Maxillarysinus

Mandibularangle

Bite guideof scanner25

16

17

Condylarprocess

Mandibular (glenoid) fossa

Orbit

26272829

30

31

32Third molar

(wisdom tooth)

1

Fig. 9.7 Dental panoramic tomogramThedentalpanoramictomogram(DPT)isasurveyradiographthatal-lowsapreliminaryassessmentofthetemporomandibularjoints,max-illary sinuses, maxilla, mandible, and dental status (carious lesions,location of the wisdom teeth). It is based on the principle of conven-tional tomography inwhich thex-ray tubeandfilmaremovedaboutthe plane of interest to blur out the shadows of structures outside the sectionalplane.TheplaneofinterestintheDPTisshapedlikeaparab-ola,conformingtotheshapeof the jaws. In thecaseshownhere,allfourwisdomteeth(thirdmolars)shouldbeextracted:teeth1,16,and

17arenotfullyerupted,andtooth32ishorizontallyimpacted(cannoterupt).IftheDPTraisessuspicionofcariesorrootdisease,itshouldbefollowedwithspotradiographssothatspecificregionsofinterestcanbeevaluatedathigherresolution.(TomogramcourtesyofProf.Dr.U. J.Rother,directorof theDepart-mentofDiagnosticRadiology,CenterforDentistryandOromaxillofacial Surgery,EppendorfUniversityMedicalCenter,Hamburg,Germany.)

Note:Theupperincisorsarebroaderthanthelowerincisors,leadingtoa“cusp-and-fissure”typeofocclusion(seep.183).

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Root

Neck(cementoenamel

junction)

Crown

A

Crown

Neck

Root

Enamel

Dentine

Pulp chamber

Gingival margin

Alveolar bone

Cementum

Apex of root

B

Cusp of tooth

Periodontal ligament

Apical foramen

Table 9.1 Structures of the tooth

Protective coverings:Thesehard,avascular layers of tissue protect the underlyingbodyofthetooth.Theymeetatthecervicalmargin(neck,cementoenamel junction).

Enamel:Hard,translucentcoveringofthecrownofthetooth.Maximumthickness(2.5mm)occursoverthecusps.Theenamelcoveringmeetsthecementumattheneck(cervicalmargin,cementoenameljunc-tion).Failuretodosoexposestheunderlyingdentine,whichhasextremelysensitivepainresponses.

Cementum:Bonelikecoveringofthedentalroots,lackingneurovascularstructures.

Body of the tooth: The tooth is primarily composedofdentine,whichissupportedby the vascularized dental pulp.

Dentine:Toughtissuecomposingthemajorityofthebodyofthetooth.Itconsistsofextensivenetworksoftubules(intratubulardentine)surroundedbyperitubulardentine.Thetubulesconnecttheunderlyingdentalpulptotheoverlyingtissue.Exposeddentineisextremelysensitiveduetoextensiveinnervationvia the dental pulp.

Dental pulp:Locatedinthepulpchamber,thedentalpulpisawell-vascularizedlayeroflooseconnectivetissue. Neurovascular structures enter the apical foramen at the apex of the root. The dental pulp receivessympatheticinnervationfromthesuperiorcervicalganglionandsensoryinnervationfromthetrigeminalganglion(CNV).

Periodontium: The tooth is anchored andsupportedbytheperiodontium,which consists of several tissue types. Note: The cementum is also considered part of the periodontium.

Periodontal ligament: Denseconnectivetissuefibersthatconnectthecementumoftherootsintheosseous socket to the alveolar bone.

Alveolar bone (alveolar processes of maxilla and mandible): The portion of the maxilla or mandible in which the dental roots are embedded are considered the alveolar processes (the more proximal portion of the bones are considered the body).

Gingiva:Theattachedgingivaebindthealveolarperiosteumtotheteeth;thefreegingivacomposesthe 1mmtissueradiussurroundingtheneckofthetooth.Amucosogingivallinemarkstheboundarybetweenthekeratinizedgingivaeofthemandibulararchandthenonkeratinizedlingualmucosa.Thepalatalmucosaismasticatory(orthokeratinized),sonovisualdistinctioncanbemadewiththegingiva ofthemaxillaryarch.Thirdmolars(wisdomteeth)ofteneruptthroughthemucosogingivalline.Theoralmucosacannotsupportthetooth,andfoodcanbecometrappedintheregionslackingattachedgingiva.

Fig. 9.8 Parts of the toothA Individual tooth (mandibular molar). B Crosssection of a tooth (mandibular incisor). The teeth consist of an enamel-covered crown that meets the cementum-covered roots at the neck (cervicalmargin).Thebodyofthetoothispri-marily dentine.

182


Structure of the Teeth

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Decussatinginterdental

fibers

Circularfibers

Interdentalpapilla

Gingiva

Alveolar wall

Sharpey fibers

Cementum

A B

A

Occlusalplanes

MolarsPremolars

Canine

Incisors

B C

Fig. 9.9 PeriodontiumThe tooth is anchored in the alveolus by a special type of syndesmosis (gomphosis).Theperiodontium,theall-encompassingtermforthetis-suesthatcollectivelyinvestandsupportthetooth,consistsof:

• Cementum• Periodontalligament• Alveolarwallofalveolarbone• Gingiva

TheSharpeyfibersarecollagenousfibersthatpassobliquelydownwardfrom the alveolar bone and insert into the cementum of the tooth. This downwardobliquityofthefiberstransformsmasticatorypressuresonthedentalarchintotensilestressesactingonthefibersandanchoredbone (pressure would otherwise lead to bone atrophy).

Fig. 9.10 Connective tissue fibers in the gingivaManyofthetoughcollagenousfiberbundlesintheconnectivetissuecoreofthegingivaabovethealveolarbonearearrangedinascrewlikepatternaroundthetooth,furtherstrengtheningitsattachment.

Fig. 9.11 Occlusal plane and dental archesA Occlusal plane. The maxilla and mandible present a symmetrical

arrangementofteeth.Theocclusalplane(formedwhenthemouthisclosed)oftenformsasuperiorlyopenarch(vonSpeecurve,red).

B Cusp-and-fissure dentition. With the mouth closed (occlusal posi-tion),themaxillaryteethareapposedtotheirmandibularcounter-parts.Theyareoffset relative tooneanother so that thecuspsof

onetoothfitintothefissuresofthetwoopposingteeth(cusp-and-fissure dentition, blue). Because of this arrangement, every toothcomesintocontactwithtwoopposingteeth.Thisoffsetresultsfromtheslightlygreaterwidthofthemaxillaryincisors.

C Dental arches.Theteethofthemaxilla(green)andmandible(blue)arearrangedinsuperiorandinferiorarches.Thesuperiordentalarchformsasemi-ellipse,andtheinferiorarchisshapedlikeaparabola.

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PalatalDistalLabial

B

PalatalDistalLabial

A

Incisaledge

Labial Distal

C

Central incisors

Root(flattenedmesiodistally)

Labialcusp

PalatalDistalLabialA Occlusal

Labialcusp

LingualDistalLabialB

Table 9.2 Incisors and canines

Tooth Crown Surfaces Root(s)

Incisors:Theincisorshaveasharp-edgedcrownforbitingoffbitsoffood.Thepalatalsurfaceoftenbearsablindpit(foramencecum),asiteofpredilectionfordentalcaries.Themaxillaryincisorsareconsiderablylargerthanthemandibularincisors.Thisresultsincusp-and-fissuredentition (see Fig. 9.11).

Maxillary Centralincisor(8,9);seeFig. 9.12A Roughlytrapezoidalinthelabialview;containsanincisaledgewith3tubercles(mamelons)

Labial:Convex Palatal:Concavoconvex

1 rounded root

Lateralincisor(7,10);seeFig. 9.12B

Mandibular Centralincisor(25,24);seeFig. 9.12C Labial:Convex Lingual:Concavoconvex

1root,slightlyflattened

Lateralincisor(26,23)seeFig. 9.12C

Canines:Theseteeth(alsoknownascuspidsoreyeteeth)aredevelopedforpiercingandgrippingfood.Thecrownisthickermesiallythandistallyandhasgreatercurvature(arrow,Fig. 9.13A).

Maxillary(upper)canine(6,11);seeFig. 9.13A Roughlytrapezoidalwith1labialcusp

Labial:Convex Palatal:Concavoconvex

1root,thelongest of the teeth (note: mandibular canines are occasionallybifid)Mandibular(lower)canine(27,22);seeFig. 9.13B Labial:Convex

Lingual:Concavoconvex

Fig. 9.12 IncisorsA Centralmaxillaryincisor(9).B Lateral maxillary incisor (10). C Mandibularincisors(23–26).

Fig. 9.13 Canines (cuspids)A Maxillary canine (11). B Mandibularcanine(22).

184


Incisors, Canines & Premolars

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Mesiodistalfissure

DistalBuccalA

Buccalroot

Buccalcusp

Palatal root

Occlusal

Palatalcusp

Longitudinal groove

DistalBuccalB Occlusal

Distalocclusal pit

DistalBuccalC

Buccalcusp

Mesialocclusal pit

Occlusal

Mesiodistalfissure

DistalBuccalD Occlusal

Buccal cusp

Table 9.3 Premolars

Thepremolarsrepresentatransitionalformbetweentheincisorsandmolars.Likethemolars,theyhavecuspsandfissures,indicatingthattheirprimaryfunctionisthegrindingoffoodratherthanbitingortearing.


Maxillary 1stpremolar(5,12);see Fig. 9.14A

2cusps(1buccal,1palatal,separatedbyamesodistalfissure)

Buccal, distal, palatal/lingual, and mesial:Allconvex,slightlyflattened.The mesial surface often bears a smallpitthatisdifficulttocleanandvulnerable to caries.

Occlusal: The occlusal surfaces of the maxillary premolars tend to be more oval(lesscircularorsquare)thanthemandibular premolars.

Theonlypremolarwith2roots(1buccal,1palatal)

2ndpremolar(4,13);see Fig. 9.14B

1 root divided by a longitudinalgrooveandcontaining2rootcanals

Mandibular 1stpremolar(28,21);see Fig. 9.14C

2cusps(1tallbuccalcuspconnectedto1smallerlingualcusp);theridgebetweenthecusps creates a mesial and a distal occlusal pit

1root(occasionallybifid)

2ndpremolar(29,20);see Fig. 9.14D

3cusps(1tallbuccalcuspseparatedfrom2smallerlingualcuspsbyamesiodistalfissure)

1 root

Fig. 9.14 Premolars (bicuspids)A Firstmaxillarypremolar(12).B Secondmaxillarypremolar(13). C Firstmandibularpremolar(21).D Secondmandibularpremolar(20).

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Table 9.4 Molars

Mostofthemolarshavethreerootstowithstandthegreatermasticatorypressuresinthemolarregion.Becausethemolarscrushandgrindfood, theyhaveacrownwithaplateau.Thefissuresbetweenthecuspsareafrequentsiteofcariesformationinadolescents.Note: The roots of the third molars(wisdomteeth,whicheruptafter16yearsofage,ifatall)arecommonlyfusedtogether,particularlyintheupperthirdmolar.Themandibularthirdmolarseruptanterosuperiorly,andthemaxillarythirdmolarseruptposteroinferiorly.Impactionsarethereforemostcommoninmandibularwisdom teeth.


Maxillary 1stmolar(3,14);see Fig. 9.15A

4cusps(1ateachcornerofitsocclusalsurface);aridgeconnectsthemesiopalatal and distobuccal cusps

Buccal, distal, palatal/lingual, and mesial:Allconvex,slightlyflattened.

Occlusal:Rhomboid

3roots(2buccaland1palatal)

2ndmolar(2,15);see Fig. 9.16A

4cusps(thoughthedistopalatalcuspisoften small or absent)

3roots(2buccaland1palatal),occasionally fused

3rdmolar(wisdomtooth,1,16);seeFig. 9.17A

3cusps(nodistopalatal) 3roots(2buccaland1palatal),often fused

Mandibular 1stmolar(30,19);see Fig. 9.15B

5cusps(3buccaland2lingual),allofwhichareseparatedbyfissures

Buccal, distal, palatal/lingual, and mesial:Allconvex,slightlyflattened.

Occlusal:Rectangular

2roots(1mesialand1distal);widely spaced

2ndmolar(31,18);see Fig. 9.16B

4cusps(2buccaland2lingual) 2roots(1mesialand1distal)

3rdmolar(wisdomtooth,32,17);seeFig. 9.17B

Mayresembleeitherthe1stor2ndmolar

2roots,oftenfused

186


Molars

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Mesio-palatalcusp

PalatalDistalBuccalA

Palatal root

Occlusal

Disto-buccalcusp

OcclusalPalatalDistalBuccalA

Palatal root

Disto-palatalcusp

OcclusalPalatalDistalBuccalA

Palatal root (fusedwith buccal roots)

OcclusalLingualDistalBuccalB OcclusalLingualDistalBuccalB

OcclusalLingualDistalBuccalB

Fig. 9.15 First molarsA Maxillaryfirstmolar (14).B Mandibularfirstmolar (19).Note: The term lingual isusedforthemandibularteeth,thetermpalatal for the maxillary.

Fig. 9.17 Third molars (wisdom teeth)A Maxillary third molar (16). B Mandibularthirdmolar(17).

Fig. 9.16 Second molarsA Maxillarysecondmolar(15).B Mandibular second molar (18).

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A B C D E

12 years

10 years

8 years

6 years

4 years

2½ years

1 year

6 months

Birth

Table 9.5 Eruption of the teeth

The eruptions of the deciduous and permanent teeth are called the firstandseconddentitions,respectively.Typesofteethareorderedbythetimeoferuption;individualteetharelistedfromlefttoright(viewer’s perspective).

Type of tooth Tooth Time of eruption

First dentition (deciduous teeth)

Centralincisor E,F P,O 6–8months

Lateral incisor D,G Q,N 8–12months

First molar B,I S,L 12–16months

Canine C,H R,M 15–20months

Second molar A,J T,K 20–40months

Second dentition (permanent teeth)

First molar 3,14 30,19 6–8years(“6-yrmolar”)

Centralincisor 8,9 25,24 6–9years

Lateral incisor 7,10 26,23 7–10years

First premolar 5,12 28,21 9–13years

Canine 6,11 27,22 9–14years

Second premolar 4,13 29,20 11–14years

Second molar 2,15 31,18 10–14years(“12-yrmolar”)

Third molar 1,16 32,17 16–30years(“wisdomtooth”)

Fig. 9.18 Deciduous teethLeftside.Thedeciduousdentition(babyteeth)consistsofonly20teeth. Eachofthefourquadrantscontainsthefollowingteeth:

A Central incisor (first incisor). B Lateral incisor (second incisor). C Canine(cuspid).D First molar (6-yr molar). E Secondmolar(12-yrmolar).

Todistinguishthedeciduousteethfromthepermanentteeth,theyarecodedwithletters.TheupperarchislabeledAtoJ,thelowerislabeledKtoT.

Fig. 9.19 Eruption pattern of the deciduous and permanent teethLeftmaxillaryteeth.Deciduousteeth(black),permanentteeth(red).Eruptiontimescanbeusedtodiagnosegrowthdelaysinchildren.

188


Deciduous Teeth

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Infraorbitalforamen

Anteriornasal spine

Intermaxillary suture

Second deciduous molar

First deciduous molar

Deciduouscanine

Deciduouslateral incisor

Permanentcentral incisor

Secondpermanent

premolar

Firstpermanent

premolar

Permanentcanine

Permanentlateral incisorA

Second deciduousmolar

Firstdeciduous molar

Deciduouscanine


Secondpermanent molar

First permanentmolar

Second permanentpremolar

First permanentpremolar

Permanentcanine

Permanentlateral incisor


D

First per-manent molar

Second decid-uous molar

First deciduousmolar

Deciduouscanine


Deciduouscentral incisor

Second per-manent molar

Second per-manent premolar

Mentalforamen

First permanent premolar

Permanentcanine



B

E F G H I JDCBA

O N M L KPQRST

Second deciduous molarFirst decid-

uous molarDeciduous

canineDeciduous

lateral incisor

Deciduouscentral incisor

Second permanent molar

First permanent molar

Second permanent premolar

Firstpermanent

premolar

Permanentcanine


C

Fig. 9.21 Dentition of a 6-year-old childAnterior (A,B) and left lateral (C,D) views of maxillary (A,C) and mandibular (B,D) teeth. The anterior bony plate over the roots of the deciduous teeth has been removed to display theunderlyingpermanenttoothbuds(blue).At6yearsofage,allthedeciduousteethhaveeruptedandare still present, alongwith thefirstpermanenttooth,thefirstmolar.

Fig. 9.20 Coding the deciduous teethThe upper right molar is considered A. Thelettering then proceeds clockwise along theupper arc and back across the lower.

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Floor of maxillary sinus (palatine and alveolar processes)

Palatine bone,perpendicular

plate

Palatine bone,horizontal plate

Palatine process of maxilla(floor of nasal cavity)

A

Alveolar processof maxilla

Lateral pterygoid plateof sphenoid bone

Medial pterygoid plate of sphenoid bonePalatine bone,

pyramidal process

Vomer

Sphenoidbone

Palatine bone,horizontal plate

Maxilla, palatineprocess (roof oforal cavity)

Choanae

B

Maxilla, zygomaticprocess

Maxilla, alveolar process

Palatine bone,pyramidal process

Incisive fossa

Choanae

Middle nasal concha (ethmoid bone)

VomerSphenoid

bone, lateral pterygoid plate Palatine bone,

horizontal plate

Maxilla, palatine process

Palatine bone,pyramidal process

C

Maxilla, zygomatic process

Maxilla, alveolarprocess

Inferior nasal concha

Incisive fossa (openingof incisive canal)

Fig. 9.22 Hard palate in the skull baseInferior view.

Fig. 9.23 Bones of the hard palateA,C Superior view. The upper part of the

maxilla is removed. The floor of the nasalcavity (A) and the roof of the oral cavity (B) are formed by the union of the palatine processes of two maxillary bones with the horizontal plates of two palatine bones. Cleftpalate results froma failed fusionofthe palatine processes at the median pala-tine suture.

B,D Inferior view. The nasal cavity commu-nicates with the nasopharynx via the choa-nae,whichbeginattheposteriorborderofthe hard palate. The two nasal cavities com-municate with the oral cavity via the inci-sive canals (D),whichcombineandemergeat the incisive foramen (E).

C,E Oblique posterior view. This view illus-trates the close anatomical relationship be-tween the oral and nasal cavities. Note: The pyramidal process of the palatine bone is integratedintothelateralplateoftheptery-goidprocessofthesphenoidbone.Thepal-atinemarginofthevomerarticulateswiththehardpalatealongthenasalcrest.

190


Hard Palate

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Greaterpalatine canal Palatine bone,

pyramidal process

Pterygoid process,lateral plate (sphenoid bone)

Pterygoid process, medialplate (sphenoid bone)

Palatine bone, perpendicular plate

Palatine bone,posterior nasal spine


Palatine processof maxilla

Maxillarysinus

Nasal crest(cut)

Anterior nasal spine (cut)

Incisivecanal

D

Incisive foramen(opening of

incisive canal)

Inferiororbital fissure

Choana

Posteriornasal spine

Vomer

Pterygoid fossa

Foramenovale

Pterygoid process,lateral plate

Pterygoid process,medial plate

Pyramidal processof palatine bone

Lesser palatine foramen

Greaterpalatine foramen

Palatine process of maxilla

Median (intermaxillary) palatine suture

E


Pterygoidcanal

Septum ofsphenoid sinus

Opticcanal

Anteriorclinoid process

Superior orbital fissure

Inferiororbital fissure

Choana

Medianpalatine suture

Incisiveforamen Palatine process of maxilla



Pterygoidfossa

Inferior concha

Ethmoid bone, perpendicular plate

Middle concha

Ostium ofsphenoid sinus

F

Vomer

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Ramusof mandible

Obliqueline

Alveoli(toothsockets)

Mentalprotuberance

Body ofmandible

Alveolarpart of

mandible

Coronoidprocess

Head (condyle) of mandible

A

Condylarprocess

Mylohyoidline

Mandibularforamen

Coronoidprocess


B

Lingula

Submandibularfossa

Superior andinferior genial (mental) spines

Digastricfossa

Mylohyoidgroove

C

Angle

Obliqueline

Mentalforamen

Alveolarpart

Mentaltubercle

Mandibularforamen

Mandibularnotch

Coronoidprocess

Ramusof mandible

Pterygoid fovea


Condylar process

Fig. 9.24 MandibleA Anterior view. B Posterior view. C Oblique left lateral view. Themandibular teeth are embedded in the alveolar processes of the man-diblethatrunalongthesuperiorborderofthebodyofthemandible.The vertical ramus joins the body of the mandible at the mandibular angle.The ramuscontainsacoronoidprocess (siteofattachmentofthe temporalis) and a condylar process that are separated by the man-dibular notch. The convex surface of the condylar process (the head of

themandible)articulatesviaanarticulardiskwiththemandibular(gle-noid) fossa of the temporal bone at the temporomandibular joint (see p.194).Thedepressionontheanteromedialsideofthecondylarpro-cess(pterygoidfovea)isasiteofattachmentofthelateralpterygoid.The inferior alveolar nerve (a branch of CNV3) enters the mandibu-larforamenandrunsthroughthemandibularcanalinthebodyofthemandible,exitingthementalforamenasthementalnerve.

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Mandible & Hyoid Bone

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B

C

D

A

Greater hornLesser horn

BodyA

Greater hornLesser horn

BodyB

Greater horn

Lesser horn

C

Fig. 9.25 Age-related changes in the mandibleThe structure of the mandible is greatly influenced by the alveolar processes of the teeth. Because the angle of the mandible adaptsto changes in thealveolarprocess, theanglebetween thebodyandramusalsovarieswithage-relatedchangesinthedentition.Theanglemeasuresapproximately150degreesatbirth,andapproximately120to130degreesinadults,decreasingto140degreesintheedentulousmandibleofoldage.

A At birththemandibleiswithoutteeth,andthealveolarparthasnotyet formed.

B In children the mandible bears the deciduous teeth. The alveolar part is still relatively poorly developed because the deciduous teeth are considerably smaller than the permanent teeth.

C In adults themandiblebearsthepermanentteeth,andthealveolarpart of the bone is fully developed.

D Old age is characterized by an edentulous mandible with resorption of the alveolar process.

Note: Theresorptionofthealveolarprocesswithadvancedageleadstoachangeinthepositionofthementalforamen(whichisnormallylocated belowthesecondpremolartooth,asinC).Thischangemustbetakenintoaccountinsurgeryordissectionsinvolvingthementalnerve.

Fig. 9.26 Hyoid boneA Anterior view. B Posterior view. C Oblique left lateral view. Thehyoidboneissuspendedbymusclesandligamentsbetweentheoral

floorandthelarynx.Thegreaterhornandbodyofthehyoidbonearepalpable intheneck.Thephysiologicalmovementofthehyoidbonecanbepalpatedduringswallowing.

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Petrotympanicfissure

Articulartubercle

Mandibularfossa of TMJ

Externalacoustic meatus(auditory canal)

Zygomatic processof temporal bone

Styloid process

Mastoid process

Postglenoidtubercle

Atlanto-occipital joint

Stylomandibular ligament

Joint capsule

Lateral ligament

Mylohyoid groove

Mandibular foramen

Lingula

Neck of mandible

Neck ofmandible

Coronoidprocess

Pterygoidfovea


A B

Fig. 9.27 Mandibular fossa of the TMJInferior view of skull base. The head (condyle) of the mandible artic-ulates with the mandibular fossa of the temporal bone via an articu-lardisk.Themandibularfossaisadepressioninthesquamouspartofthetemporalbone,boundedbyanarticulartubercleandapostglenoid

Fig. 9.28 Head of the mandible in the TMJA Anterior view. B Posteriorview.Thehead(condyle)ofthemandibleismarkedly smaller than the mandibular fossa and has a cylindrical shape. Both factors increase themobility of themandibular head, allowing rotational movements about a vertical axis.

Fig. 9.29 Ligaments of the lateral TMJLeftlateralview.TheTMJissurroundedbyarelativelylaxcapsulethatpermitsphysiologicaldislocationduringjawopening.Thejointisstabi-lizedbythreeligaments:lateral,stylomandibular,andsphenomandib-ular (see also Fig. 9.30).Thestrongestoftheseligamentsisthelateralligament,whichstretchesoverandblendswiththejointcapsule.

tubercle.Unlikeotherarticular surfaces, themandibular fossa iscov-ered by fibrocartilage, not hyaline cartilage. As a result, it is not asclearly delineated on the skull (compare to the atlanto-occipital joints). The external auditory canal lies just posterior to the mandibular fossa. Traumatothemandiblemaydamagetheauditorycanal.

194


Temporomandibular Joint (TMJ)

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Stylomandibularligament

Sphenomandib-ular ligament

Mandibularnotch

Pterygospinousligament

Joint capsule

Stylomandibular ligament


Articular disk

Articulartubercle

Postglenoidtubercle

Mandibular nerve (CN V3)

Masseteric nerve

Deep temporal nerve, posterior branch

Auriculotemporalnerve

Posterior division

Anterior division

Fig. 9.33 Sensory innervation of the TMJ capsuleSuperiorview.TheTMJcapsule issuppliedbyarticularbranchesaris-ingfromthreenervesfromthemandibulardivisionofthetrigeminalnerve(CNV3):

• Auriculotemporalnerve• Deeptemporalnerve,posteriorbranch• Massetericnerve

Fig. 9.30 Ligaments of the medial TMJLeftmedial view.Note thesphenomandibular ligament.Thevariablepterygospinousligamentisalsopresent.

Fig. 9.31 Opened TMJLeftlateralview.TheTMJcapsulebeginsatthearticulartubercleandextendsposteriorlytothepetrotympanicfissure(seeFig. 9.27). Inter-posedbetweenthemandibularheadandfossaisthefibrocartilaginousarticulardisk,whichisattachedtothejointcapsuleonallsides.

Fig. 9.32 Dislocation of the TMJThe head of the mandible may slide past the articular tubercle when themouthisopened,dislocatingtheTMJ.Thismayresultfromheavyyawningorablowtotheopenedmandible.Whenthejointdislocates,themandiblebecomeslockedinaprotrudedpositionandcannolonger beclosed.Thisconditioniseasilydiagnosedclinicallyandisreducedbypressingonthemandibularrowofteeth.

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Median plane

Head of mandible

Transverse axis throughhead of mandible(axis of rotation)

150°

AProtrusion

Retrusion

B

Working side(laterotrusion)

Balance side(mediotrusion)

Bennett angle

Axis ofrotation

Resting condyle

Swingingcondyle

C

Balance sideWorking side

D

Axis ofrotation

Fig. 9.34 Movements of the mandible in the TMJSuperiorview.MostofthemovementsintheTMJarecomplexmotionsthat have three main components:

• Rotation(openingandclosingthemouth)• Translation(protrusionandretrusionofthemandible)• Grindingmovementsduringmastication

A Rotation. The axis for joint rotation runs transversely throughbothheadsofthemandible.Thetwoaxesintersectatanangleofapproximately150degrees(rangeof110to180degreesbetweenindividuals). During thismovement the TMJ acts as a hinge joint(abduction/depression and adduction/elevation of the mandible). Inhumans,purerotationintheTMJusuallyoccursonlyduringsleepwiththemouthslightlyopen(apertureangleuptoapproximately15degrees).Whenthemouthisopenedpast15degrees,rotationiscombinedwithtranslation(gliding)ofthemandibularhead.

B Translation. In this movement the mandible is advanced (protruded) and retracted (retruded). The axes for this movement are parallel to themedianaxesthroughthecenterofthemandibularheads.

C Grinding movements in the left TMJ. In describing these lateralmovements, a distinction ismade between the “resting condyle”andthe“swingingcondyle.”Therestingcondyleontheleftworkingsiderotatesaboutanalmostverticalaxis throughtheheadof themandible(alsoarotationalaxis),whereastheswingingcondyleontherightbalancesideswingsforwardandinwardinatranslationalmovement. The lateral excursion of the mandible is measured in de-grees and is called the Bennett angle. During thismovement themandiblemovesinlaterotrusionontheworkingsideandinmedio-trusion on the balance side.

D Grinding movements in the right TMJ.Here,therightTMJistheworkingside.Therightrestingcondylerotatesaboutanalmostver-ticalaxis,andthe leftcondyleonthebalancesideswingsforwardand inward.

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Temporomandibular Joint (TMJ): Biomechanics

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Lateral pterygoid muscle, inferior head

Head of mandible

Joint capsule

Articular disk

Articulartubercle

Lateral pterygoid muscle,superior head

A

Mandibular fossa


Joint capsule

Head of mandible


B

Articular disk

Axis of rotation15°


Joint capsule

Articular disk


C

Mandibular fossa

>15°

Fig. 9.35 Movements of the TMJLeftlateralview.EachdrawingshowstheleftTMJ,includingthearticu-lardiskandcapsuleandthelateralpterygoidmuscle.Eachschematicdiagramatrightshowsthecorrespondingaxisofjointmovement.Themuscle, capsule, and disk form a functionally coordinatedmusculo- disco-capsular system and work closely together when the mouthis opened and closed. Note: The space between the muscle heads is greatlyexaggeratedforclarity.

A Mouth closed. When themouth is in a closed position, the headofthemandiblerestsagainstthemandibularfossaofthetemporalbonewiththeinterveningarticulardisk.

B Mouth opened to 15 degrees. Upto15degreesofabduction,thehead of the mandible remains in the mandibular fossa.

C Mouth opened past 15 degrees. At this point the head of the man-dibleglidesforwardontothearticulartubercle.Thejointaxisthatruns transversely through themandibularhead is shifted forward.The articular disk is pulled forward by the superior part of the lateral pterygoidmuscle,andtheheadofthemandibleisdrawnforwardbythe inferior part of that muscle.

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①

②

④

③

⑧

⑤

⑥

⑦

Table 9.6 Masseter and temporalis muscles

Muscle Origin Insertion Innervation* Action

Masseter ①Superficialhead

Zygomaticbone(maxillaryprocess)andzygomaticarch(lateralaspectofanterior⅔)

Mandibularangleandramus (lower posterior lateral surface)

Masseteric n. (anterior division ofCNV3)

Elevatesmandible;alsoassistsinprotraction,retraction,andside-to-sidemotion

Middle head Zygomaticarch(medialaspectofanterior⅔)

Mandibular ramus (central part)

②Deephead Zygomaticarch(deepsurfaceofposterior⅓)

Mandibular ramus (upper portion) and lateral side of coronoid process

Temporalis ③Superficialhead

Temporal fascia Coronoidprocessofmandible (apex and medial and anterior surfaces)

Deeptemporalnn.(anterior division ofCNV3)

Vertical (anterior) fibers: Elevate mandible Horizontal (posterior) fibers: Retract(retrude)mandible Unilateral: Lateral movement ofmandible(chewing)

④Deephead Temporal fossa (inferior temporal line)

*Themusclesofmasticationareinnervatedbymotorbranchesofthemandibularnerve(CNV3),the3rddivisionofthetrigeminalnerve(CNV).

Table 9.7 Lateral and medial pterygoid muscles

Muscle Origin Insertion Innervation Action

Lateral pterygoid

⑤ Superior head Greaterwingofsphenoidbone(infratemporal crest)

Mandible(pterygoidfovea) and temporomandibular joint (articular disk)

Mandibular n. (CNV3) via lateral pterygoidn.(fromanterior division of CNV3)

Bilateral:Protrudesmandible (pulls articular disk forward) Unilateral: Lateral movements of mandible(chewing)⑥ Inferior head Lateralpterygoidplate(lateral

surface)Mandible(pterygoidfovea and condylar process)

Medial pterygoid

⑦Superficialhead Maxilla (maxillary tuberosity) and palatine bone (pyramidal process)

Pterygoidtuberosityon medial surface of themandibularangle

Mandibular n. (CNV3) via medial pterygoidn.(fromtrunkofCNV3)

Raises(adducts)mandible

⑧Deephead Medialsurfaceoflateralpterygoidplateandpterygoidfossa

Themuscles ofmastication are derived from the first branchial archand are located at various depths in the parotid and infratemporal re-gionsoftheface.Theyattachtothemandibleandreceivetheirmotor

Fig. 9.36 Masseter Fig. 9.37 Temporalis Fig. 9.38 Pterygoids

innervationfromthemandibulardivisionofthetrigeminalnerve(CNV3).Themusclesoftheoralfloor(mylohyoidandgeniohyoid)arefoundonpp.178,203.

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Muscles of Mastication: Overview

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Coronoidprocess

Joint capsule

Lateralpterygoid

Masseter

Lateral ligament

Temporalis

B

Zygomaticarch

Superiortemporal

line

Frontal bone Parietal boneZygomaticarch

External acoustic meatus

Mastoid process

Joint capsule

Lateral ligament

Styloid process

Masseter,deep head

Masseter,superficial head

Temporalis

A

Superior temporal line

Fig. 9.39 Temporalis and masseterLeft lateral view.

A Superficialdissection.B Deep dissection. The masseter and zygo-

matic arch have been partially removed to show the full extent of the temporalis.

The temporalis is the most powerful muscle ofmastication, doing approximatelyhalf thework. Itworkswith themasseter (consistingofasuperficialandadeeppart)toelevatethemandible and close the mouth. Note: A small portionofthelateralpterygoidisvisibleinB.

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Masseter (cut)

Medial pterygoid,superficial and deep heads

Lateral pterygoid,superior andinferior heads

Temporalis (cut)

A

Lateral plate, pterygoid process (sphenoid bone)

Medial pterygoid,deep head

Lateral pterygoid,inferior head (cut)

Articulardisk

Lateral pterygoid,superior head (cut)

BMedial pterygoid,superficial head

Articular disk

Head of mandible,articular surface

Masseter, superficial part

Medial pterygoid,deep head

Masseter, deep part

Lateral pterygoid, inferior head

Lateral pterygoid, superior head

Temporalis

Mandibular angle

Pterygoid process, medial plate

Mandibular fossa, articular surface

Lateral pterygoid, inferiorhead, in pterygoid fovea

Coronoid process(with temporalis)

Fig. 9.40 Lateral and medial pterygoid musclesLeft lateral views.A Thecoronoidprocessofthemandiblehasbeenremovedherealong

withthelowerpartofthetemporalissothatbothpterygoidmusclescan be seen.

B Here the temporalishasbeencompletely removed,and the supe-riorandinferiorheadsofthelateralpterygoidhavebeenwindowed.The lateralpterygoidinitiatesmouthopening,whichisthencontin-uedbythedigastricandthesuprahyoidmuscles,alongwithgravity.

Withthetemporomandibular jointopened,wecanseethatfibersfromthelateralpterygoidblendwiththearticulardisk.Thelateralpterygoidfunctionsastheguidemuscleofthetemporomandibularjoint.Becausebothitssuperiorandinferiorheadsareactiveduringallmovements,itsactionsaremorecomplexthanthoseoftheothermuscles of mastication. The medialpterygoid runsalmostperpen-diculartothelateralpterygoidandcontributestotheformationofamuscularsling,alongwiththemasseter,thatpartiallyencompassesthe mandible (see Fig. 9.41).

Fig. 9.41 Masticatory muscular sling

Obliqueposteriorview.Themasseterand medialpterygoidformamuscu-larslinginwhichthemandibleissus-pended.Bycombiningtheactionsofbothmusclesintoafunctionalunit,this sling enables powerful closureof the jaws.

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Muscles of Mastication: Deep Muscles

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Ethmoidair cells

Sphenoidsinus

Nasopharynx

Parotid gland

Oropharynx

Tongue

Submandibulargland

Mylohyoidmuscle

Digastric muscle,anterior belly

Platysma

Masseter, superficial head

Masseter, deep head

Lateral pterygoid, inferior head

Temporalis, superficial and deep heads

Lateral pterygoid, superior head

Medial pterygoid,deep and superficial heads

Superior sagittal sinus

Dura materTemporal

lobe

Optic nerve (CN II)

Frontallobe

Falx cerebri

Mandible

Geniohyoidmuscle

Temporalfascia

Zygomaticarch

Pterygoidprocess,

lateral plate

Hyoglossus

Inferior alveolar nerve(CN V3) in mandibularcanal

Lingual septum

Inferiorsagittal sinus

Fig. 9.42 Muscles of mastication, coronal section at the level of the sphenoid sinusPosteriorview.

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Mylohyoidraphe

1b

1a

②

④

③

B

②

③

④

1b

1a

A

Table 9.8 Suprahyoid muscles


Suprahyoid muscles: The suprahyoid muscles are also considered accessory muscles of mastication.

Digastric 1a Anterior belly Mandible(digastricfossa) Hyoidbone (body)

Viaanintermediatetendon with a fibrousloop

Mylohyoid n. (fromCNV3)

Elevateshyoidbone(duringswallowing);assistsindepressingmandible

1b Posteriorbelly Temporal bone (mastoid notch,medialtomastoidprocess)

Facial n. (CNVII)

② Stylohyoid Temporal bone (styloid process)

Viaasplittendon

③ Mylohyoid Mandible (mylohyoid line) Viamediantendonof insertion (mylohyoid raphe)

Mylohyoid n. (fromCNV3)

Tightensandelevatesoralfloor;drawshyoidboneforward(duringswallowing);assistsinopeningmandibleandmovingitsidetoside(mastication)

④Geniohyoid Mandible(inferiorgenial[mental] spine)

Bodyofhyoidbone VentralramusofC1

Drawshyoidboneforward(duringswallowing);assistsinopeningmandible

Fig. 9.43 Suprahyoid muscles: schematicA Left lateral view. B Superior view.

The suprahyoid and infrahyoid muscles attach to the hyoid bone infe-riorlyandsuperiorly,respectively.Theinfrahyoidmusclesdepressthe

hyoidduringphonationandswallowing.Theyarediscussedwith thesuprahyoidmusclesandlarynxintheneck(seep.255).

202


Suprahyoid Muscles

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Sublingualfold

Genioglossus(cut)

Geniohyoid

Mylohyoid

Hyoid bone

Oral mucosa

Sublingualpapilla

Stylohyoid

Hyoglossus

B

Mylohyoid

Digastric(anterior belly)

Hyoglossus

Hyoid boneInfrahyoid muscles (sternohyoid,

thyrohyoid, and omohyoid)

Connective tissue sling

Digastric(intermediate tendon)

Stylohyoid

Digastric(posterior belly)

Mastoid process

Styloid process

A

Fig. 9.44 Suprahyoid musclesA Left lateral view. B Superior view.

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Table 9.9 Muscles of the tongue


Extrinsic lingual muscles

Genioglossus Mandible(superiorgenial[mental] spine via an intermediatetendon);more posteriorly the two genioglossiareseparatedbythelingualseptum

Inferiorfibers:Hyoidbody(anterosuperior surface)

Hypoglossaln.(CNXII) Protrusionofthetongue Bilaterally: Makes dorsum concave Unilaterally:DeviationtooppositesideIntermediatefibers:

Posteriortongue

Superiorfibers:Ventralsurfaceoftongue(mixwith intrinsic muscles)

Hyoglossus Hyoidbone(greatercornu and anterior body)

Lateraltongue,betweenstyloglossusandinferiorlongitudinalmuscle

Depressesthetongue

Styloglossus Styloid process of temporal bone (anterolateral aspect of apex) and stylomandibu-larligament

Longitudinalpart:Dorsolateraltongue(mixwithinferiorlongitudinalmuscle)

Superior and posterior movement of the tongue

Obliquepart:Mixwithfibersofthehyoglossus

Palatoglossus Palatineaponeurosis(oralsurface)

Lateraltonguetodorsumandfibersofthetransverse muscle

Vagusn.(CNX)viathepharyngealplexus

Elevatestherootofthetongue;closestheoropharyngealisthmusbycontractingthepalatoglossalarch

Intrinsic lingual muscles

Superior longitudinalmuscle

Thinlayerofmuscleinferiortothedorsalmucosa;fibersrunanterolaterallyfromtheepiglottisandmedianlingualseptum

Hypoglossaln.(CNXII) Shortenstongue;makesdorsumconcave(pullsapexandlateralmarginupward)

Inferior longitudinalmuscle

Thinlayerofmusclesuperiortothegenioglossusandhyoglossus;fibersrunanteriorlyfromtheroottotheapexofthetongue

Shortenstongue;makesdorsumconvex(pulls apex down)

Transverse muscle

Fibersrunlaterallyfromthelingualseptumtothelateraltongue

Narrowstongue;elongatestongue

Verticalmuscle

Intheanteriortongue,fibersruninferiorlyfromthedorsumofthetonguetoitsventralsurface

Widensandflattenstongue

Thereare twosetsof lingualmuscles:extrinsicand intrinsic.Theex-trinsicmuscles,whichareattachedtospecificbonysitesoutsidethetongue,movethetongueasawhole.Theintrinsicmuscles,whichhave

noattachmentstoskeletalstructures,altertheshapeofthetongue.Withtheexceptionofthepalatoglossus,thelingualmusclesaresup-pliedbythehypoglossalnerve(CNXII).

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Lingual Muscles

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Dorsum of tongue

Genio-glossus

Genio-hyoid

Hyoid bone

Hyoglossus

Styloglossus

Styloidprocess

Palato-glossus (cut)

A

Mandible

Apex oftongue Stylomandibular ligament

Stylopharyngeus

Middle pharyngeal constrictor

Inferior pharyngeal constrictor

Lingualaponeurosis

Superior longi-tudinal muscle

Inferior longi-tudinal muscle

Hyoglossus

Genioglossus

Geniohyoid

Mylohyoid

Sublingualgland

Transversemuscleof tongue

Vertical muscleof tongue

Lingualmucosa

B

Lingual septum

Anterior bellyof digastric

Apex of tongue

Paralyzedgenioglossuson affectedside

BA

Fig. 9.45 Extrinsic and intrinsic lingual muscles

A Left lateral view. B Anterior view of coronal section.

Fig. 9.46 Unilateral hypoglossal nerve palsy Activeprotrusionofthetonguewithanintacthypoglossalnerve(A) and withaunilateralhypoglossalnervelesion(B).Whenthehypoglossalnerveisdamagedononeside,thegenioglossusmuscleisparalyzedontheaffectedside.Asaresult,thehealthy(inner-vated)genioglossusontheoppositesidedominatesthetongueacrossthemidlinetowardtheaffectedside.Whenthetongue isprotruded,therefore,itdeviatestoward the paralyzed side.

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Palatopharyngealarch

Palatinetonsil

Palato-glossal

arch

Lingualtonsil

Sulcusterminalis

Medianfurrow

Dorsum

Apex

Anterior(oral) part

Posterior(pharyngeal)part

Foramencecum

Epiglottis

See detail in Fig. 9.48A

Vallatepapilla

Filiformpapillae

Lingual muscles

Lingual aponeurosis

Nonkeratinized, stratifiedsquamous epithelium

Fungiformpapilla

A

SulcusPapilla

Taste buds

Excretoryduct of a

serous gland

Wall of papilla

B

Serousglands(von Ebnerglands)

Connectivetissue cox

Tip of papilla(partially covered

by keratinizedepithelium)

C

Keratinized squamousepithelium ontips of papillae

D

Serousgland

Excretoryduct of gland

Taste buds

Foliatepapillae

E

Fig. 9.47 Surface anatomy of the lingual mucosaSuperior view. The tongue is endowedwith a very powerfulmuscu-larbody,makingpossibleitsmotorfunctionsinmastication,swallow-ing, and speaking.However, its equally important sensory functions(includingtasteandfinetactilediscrimination)aremadepossiblebythespecializedmucosalcoatcoveringthedorsumofthetongue.Thepartsofthetonguecanbediscussedasaroot,aventral(inferior)sur-face,anapex,andadorsalsurface.TheV-shapedfurrowonthedorsum(sulcus terminalis) divides the dorsal surface into an oral portion (com-prisingtheanteriortwothirds)andapharyngealportion(comprisingthe posterior one third).

Fig. 9.48 Papillae of the tongueThe mucosa of the anterior dorsum is composed of numerous papillae (A),andtheconnectivetissuebetweenthemucosalsurfaceandmus-culaturecontainsmanysmallsalivaryglands.Thepapillaearedividedintofourmorphologicallydistincttypes(seeTable 9.10):

• Circumvallate(B):Encircledandcontainingtastebuds.• Fungiform (C):Mushroom-shaped and containingmechanical and

thermal receptors and taste buds.• Filiform(D): Thread-shaped and sensitive to tactile stimuli (the only

lingualpapillaewithouttastebuds).• Foliate(E):Containingtastebuds.

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Lingual Mucosa

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Table 9.10 Regions and structures of the tongue

Region Structures

Anterior (oral, presulcal) portion of the tongue

Theanterior⅔ofthetonguecontainstheapexandthemajorityofthedorsum.Itistetheredtotheoralfloorbythelingualfrenulum.•Mucosa: ◦ Dorsallingualmucosa:Thisportion(withnounderlyingsubmu-

cosa) contains numerous papillae. ◦ Ventralmucosa:Coveredwiththesamesmooth(nonkeratinized,

stratifiedsquamousepithelial)mucosathatlinestheoralfloorandgums.

• Innervation:Theanteriorportionisderivedfromthefirst(mandibu-lar)archandisthereforeinnervatedbythelingualnerve,abranchofthemandibularnerve(CNV3).

Median furrow (midline septum): Thefurrowrunninganteriorlydownthemidlineofthetongue;thiscorrespondstothepositionofthelingualseptum. Note:Musclefibersdonotcrossthelingualseptum.

Papillae (Fig. 9.48A):Thedorsalmucosa,whichhasnosubmucosa,iscovered with nipplelike projections (papillae) that increase the surface areaofthetongue.Therearefourtypes,allofwhichoccurinthepresulcalbutnotpostsulcalportionofthetongue.• Circumvallate(Fig. 9.48B):Encircledbyawallandcontaining

abundant taste buds.• Fungiform(Fig. 9.48C): Mushroom-shaped papillae located on the

lateralmarginoftheposteriororalportionnearthepalatoglossalarches.Thesehavemechanicalreceptors,thermalreceptors,andtastebuds.

• Filiform(Fig. 9.48D): Thread-shaped papillae that are sensitive to tactile stimuli. These are the only papillae that do not contain taste buds.

• Foliate(Fig. 9.48E):Locatednearthesulcusterminalis,thesecontainnumerous taste buds.

Sulcus terminalis

ThesulcusterminalisistheV-shapedfurrowthatdividesthetonguefunctionally and anatomically into an anterior and a posterior portion.

Foramen cecum:Theembryonicremnantofthepassageofthethyroidglandthatmigratesfromthedorsumofthetongueduringdevelopment.Theforamencecumislocatedattheconvergenceofthesulciterminalis.

Posterior (pharyngeal, postsulcal) portion of the tongue

Thebaseofthetongueislocatedposteriortothepalatoglossalarchesand sulcus terminalis.• Mucosa:Thesamemucosathatlinesthepalatinetonsils,pharyngeal

walls,andepiglottis.Thepharyngealportionofthetonguedoesnotcontain papillae.

• Innervation:Theposteriorportionisinnervatedbytheglossopharyn-gealnerve(CNIX).

Lingual tonsils: The submucosa of the posterior portion contains embeddedlymphnodesknownasthelingualtonsils,whichcreatetheuneven surface of the posterior portion.

Oropharynx:Theregionposteriortothepalatoglossalarch.Theoropharynx,whichcontainsthepalatinetonsils,communicateswiththeoralcavityviatheoropharyngealisthmus(definedbythepalatoglossalarches).

Glossoepiglottic folds and epiglottic valleculae:The(nonkeratinized,stratifiedsquamous)mucosalcoveringoftheposteriortongueandpharyngealwallsisreflectedontotheanterioraspectoftheepiglottis,formingonemedianandtwolateralglossoepiglotticfolds.Themedianglossoepiglotticfoldisflankedbytwodepressions,theepiglotticvalleculae.

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Nasalconchae

Soft palate

Lymphatic tissueof lateral bands

(salpingo-pharyngeal fold)

Epiglottis

Lingual tonsil (postsulcal portion of tongue)

Palatine tonsil

Uvula

Tubaltonsil

Pharyngealtonsil

Roof of pharynx(sphenoid and occipital bones)

Palatopharyngeal arch

B

Tonsillarfossa

Palatoglossalarch

Palatinetonsil

C

Enlargedpalatine tonsil

Tonsillarfossa

Uvula Palatinetonsil

Palato-pharyngeal arch

Palato-glossal arch

Softpalate

A

Fig. 9.49 Waldeyer’s ringPosteriorviewoftheopenedpharynx.Waldey-er’s ring is composed of immunocompetentlymphatic tissue (tonsils and lymph follicles). Thetonsilsare“immunologicalsentinels”sur-rounding the passageways from the mouthand nasal cavity to the pharynx. The lymph fol-liclesaredistributedoveralloftheepithelium,showingmarked regional variations.Waldey-er’sringconsistsofthefollowingstructures:

• Unpairedpharyngeal tonsil on the roof ofthe pharynx

• Pairedpalatinetonsilsintheoropharynx• Lingualtonsil,thelymphnodesembedded

inthepostsulcalportionofthetongue• Paired tubal tonsils (tonsillae tubariae),

whichmaybe thoughtofas lateralexten-sionsofthepharyngealtonsil

• Pairedlateralbandsinthesalpingopharyn-gealfold

Fig. 9.50 Palatine tonsils: location and abnormal enlargementAnterior view of the oral cavity. The palatine tonsils occupy a shallow recessoneachside,thetonsillar fossa,which is locatedbetweentheanteriorandposteriorpillars(palatoglossalarchandpalatopharyngealarch). The palatine tonsil is examined clinically by placing a tongue

depressorontheanteriorpillaranddisplacingthetonsilfromitsfossawhilea second instrumentdepressesthetongue(B).Severeenlarge-mentofthepalatinetonsil(duetoviralorbacterialinfection,asinton-sillitis)maysignificantlynarrowtheoutletof theoral cavity,causingdifficultyinswallowing(dysphagia,C).

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Pharynx & Tonsils

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Choana

Nasalseptum

Torustubarius

Softpalate

Uvula

Salpingo-pharyngeal fold

Dens of axis(C2)

Pharyngeal orificeof pharyngo-tympanic tube

Pharyngeal tonsil

A

Sphenoid sinus

Anterior arch of axis (C1)

Roof of pharynx (sphenoid and occipital bones)

Pharyngeal recess

B

Choana

Enlargedpharyngealtonsil

Lymphfollicles

LymphocytesEpithelium

ASecondary

follicles

RespiratoryepitheliumCrypts

BRemnants of sloughed

epithelial cells

Connective tissue capsule

Secondaryfollicles

Crypts

Nonkeratinized, stratifiedsquamous epithelium

C

Fig. 9.52 Histology of the lymphatic tissue of the oral cavity and pharynx

Becauseofthecloseanatomicalrelationshipbetweentheepitheliumand lymphatic tissue, the lymphatic tissue ofWaldeyer’s ring is alsodesignatedlymphoepithelialtissue.

A Lymphoepithelial tissue. Lymphatic tissue, both organized anddiffusely distributed, is found in the lamina propria of allmucousmembranes and is known as mucosa-associated lymphatic tissue (MALT). The epithelium acquires a looser texture, with abundantlymphocytes and macrophages. Besides the well-defined tonsils,smaller collections of lymph follicles may be found in the lateral

Fig. 9.51 Pharyngeal tonsil: location and abnormal enlargementSagittalsectionthroughtheroofofthepharynx.Locatedontheroof of the pharynx, the unpaired pharyngeal tonsil can be examined bymeans of posterior rhinoscopy. It is particularly well developed in (small) children andbegins to regress at6or7 yearsof age. An en-larged pharyngeal tonsil is very common in preschool-aged children(B). (Chronic recurrent nasopharyngeal infections at this age often

bands (salpingopharyngeal folds). They extend almost verticallyfrom the lateral wall to the posterior wall of the oropharynx and nasopharynx.

B Pharyngeal tonsil. Themucosalsurfaceofthepharyngealtonsilisraised into ridges thatgreatly increase itssurfacearea.Theridgesandinterveningcryptsarelinedbyciliatedrespiratoryepithelium.

C Palatine tonsil. The surface area of the palatine tonsil is increased bydeepdepressionsinthemucosalsurface(creatinganactivesur-faceareaaslargeas300cm2). The mucosa is covered by nonkerati-nized,stratifiedsquamousepithelium.

evoke a heightened immune response in the lymphatic tissue, caus-ing“adenoids”or“polyps.”)Theenlargedpharyngealtonsilblocksthechoanae,obstructingthenasalairwayandforcingthechildtobreathethroughthemouth.Becausethemouthisthenconstantlyopenduringrespirationatrest,anexperiencedexaminercanquicklydiagnosetheadenoidal condition by visual inspection.

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Nasal septum

Soft palate

Thyroid gland

Corniculate tubercle

Cuneiform tubercle

Aryepiglottic fold

Epiglottis

Root of tongue

Medial pterygoidUvula

Faucial (oropharyngeal) isthmus, posterior border

Salpingo-pharyngeal fold

Masseter

Inferior nasalturbinate

Digastric muscle, posterior belly

Stylohyoid

Middle nasalturbinate

Choanae

Pharyngeal raphe (cut)

Laryngeal inlet

Piriformrecess

Pharyngeal tonsil

Sigmoid sinus

Palatopharyngealarch

Sphenoid bone

Pharyngeal recess

Palatine tonsil

A

Trachea

Esophagus

Table 9.11 Levels of the pharynx

Theanteriorportionofthemuscularpharyngealtubecommunicateswiththreecavities(nasal,oral,andlaryngeal).Thethreeanterioropeningsdividethepharynxintothreepartswithcorrespondingvertebrallevels.

Region Level Description Communications

Nasopharynx (Epipharynx)

C1 Upperportion,lyingbetweentheroof(formedby sphenoid and occipital bones) and the soft palate

Nasal cavity Viachoanae

Tympanic cavity Viapharyngotympanictube

Oropharynx(Mesopharynx)

C2–C3 Middleportion,lyingbetweentheuvulaandtheepiglottis

Oralcavity Viaoropharyngealisthmus(formedbythepalatoglossalarch)

Laryngopharynx(Hypopharynx)

C4–C6 Lowerportion,lyingbetweentheepiglottisandtheinferiorborderofthecricoidcartilage

Larynx Vialaryngealinlet

Esophagus Viacricopharyngeus(pharyngealsphincter)

Fig. 9.53 Pharyngeal mucosa and musculaturePosterior view.A Mucosal lining.B Internal musculature. The mus-cularposteriorwallof thepharynxhasbeendividedalongthemid-

line(pharyngealraphe)andspreadopentodemonstrateitsmucosalanatomy.

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Pharynx: Divisions & Contents

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Tensor velipalatini

Circular muscle fibers of esophagus

Posterior cricoarytenoid

Transverse arytenoid


Digastric,posterior belly

Stylohyoid

Levator velipalatini

Medial pterygoid

Stylopharyngeus

Oblique arytenoid

Styloid process

Salpingo-pharyngeus

Palato-pharyngeus

Superior pharyngealconstrictor

UvulaPharyngeal

elevators

Angle of mandible

Masseter, superficialand deep heads

B


B

Nasal septum

Pharyngeal tonsil

Pharyngo-tympanic tube orifice

UvulaA

Fig. 9.54 Posterior rhinoscopyThe nasopharynx can be visually inspected by posterior rhinoscopy.

A Techniqueofholdingthetonguebladeandmirror.Theangulationof the mirror is continually adjusted to permit complete inspection of the nasopharynx.

B Compositeposterior rhinoscopic imageacquiredatvariousmirrorangles.Thepharyngotympanic (auditory) tubeorificeandpharyn-gealtonsilcanbeidentified.

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Musculusuvulae

Softpalate

Levator veli palatini

Tensor veli palatini

Uvula

Pterygoid hamulus

Palatineaponeurosis

Masticatory mucosa lining hard palate

Carotidcanal

Pharyngeal tubercle(occipital bone)

Palatine bone(posterior portionof hard palate)

Lateral plate ofpterygoid process(sphenoid bone)

B

Palato-pharyngeus

Superiorpharyngealconstrictor

Salpingo-pharyngeus


Pharyngeal tonsil

Uvula

Tubal orifice

Cartilaginous part of pharyngotympanic (auditory) tube

Medial plate of pterygoid process(sphenoid bone)

Pterygoidhamulus


Roof of pharynx(sphenoid and occipital bones)

A

Thesoftpalateistheaponeuroticandmuscularregionhangingfromthe hard palate at the posterior portion of the oral cavity. It separates the nasopharynxfromtheoropharynx.Duringswallowing,itcanbetensedto further restrict the communication between the cavities. The palato-glossusrestrictsthecommunicationbetweentheoralcavityandphar-

Fig. 9.55 Muscles of the soft palate and pharyngotympanic tubeA Posteriorview.B Inferior view.

ynx. The pharyngealmuscles elevate and constrict the pharynx (seeTable 9.12,Table 9.13,andFig. 9.56).Thoughseveralmusclesorig-inate on thepharyngotympanic (auditory) tube, only the tensor velipalatiniplaysasignificantroleinitsopening.

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Muscles of the Soft Palate & Pharynx

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Table 9.12 Muscles of the soft palate and pharyngeal elevators



Sphenoid bone (scaphoid fossa of pterygoidprocessandmedialaspectofthespine);itisconnectedto the anterolateral membranous wallofthepharyngotympanic(auditory) tube

Palatineaponeurosisandpalatine bone (horizontal plate) via a tendon that is redirected medially by the pterygoidhamulus

N. to medial pterygoid (CNV3)

Bilaterally: Tenses anterior portion of thesoftpalateandflattensitsarch,separatingthenasopharynxfromtheoropharynx.Openspharyngo-tympanic (auditory) tube. Unilaterally: Deviatessoftpalatelaterally.


Vaginalprocessandpetrouspartoftemporalbone(viaatendon,anteriortothecarotidcanal);itisconnected to the inferior portion of thecartilaginouspharyngotym-panic tube

Palatineaponeurosis(thetwo levators combine to formamuscularsling)

Vagusn. (CNX)viapharyngealplexus

Bilaterally:Pullstheposteriorportionofthesoftpalatesuperoposteriorly,separatingthenasopharynxfromthe oropharynx.

Musculus uvulae Palatinebone(posteriornasalspine) and palatine aponeurosis (superior surface)

Mucosa of the uvula Pullstheuvulaposterosuperiorly,separatingthenasopharynxfromthe oropharynx.

Palatoglossus(palatoglossalarch)

Palatineaponeurosis(oralsurface) Lateraltonguetodorsumor intrinsic transverse muscle

Pullstherootofthetonguesuperiorly and approximates the palatoglossalarch,separatingtheoral cavity from the oropharynx.

Palatopharyn-geus(palatopha-ryngealarch)

Palatineaponeurosis(superiorsurface) and posterior border of palatine bone

Thyroidcartilage(posteriorborder) or lateral pharynx

Bilaterally: Elevates the pharynx anteromedially.

Salpingo- pharyngeus

Cartilaginouspharyngotympanictube (inferior surface)

Alongsalpingopharyngealfoldtopalatopharyngeus

Bilaterally:Elevatesthepharynx;mayalsoopenthepharyngotympanictube.

Stylopharyngeus Styloid process (medial surface of base)

Lateralpharynx,mixingwithpharyngealconstrictors,palatopharyn-geus,andthyroidcartilage(posterior border)

Glosso- pharyngealn.(CNIX)

Bilaterally: Elevates the pharynx and larynx.

Table 9.13 Pharyngeal constrictors


Superior pharyngealconstrictor

Pterygopharyngeus Pterygoidhamulus(occasionallytothemedialpterygoidplate)

Occipitalbone (pharyngealtubercle of basilarpart,via median pharyngealraphe)

Vagusn.(CNX)viapharyngealplexus

Constrictstheupperpharynx

Buccopharyngeus Pterygomandibularraphe

Mylopharyngeus Mylohyoid line of mandible

Glossopharyngeus Lateraltongue

Middle pharyngealconstrictor

Chondropharyngeus Hyoid(lessercornu)andstylohyoidligament

Constrictsthemiddlepharynx

Ceratopharyngeus Hyoid(greatercornu)

Inferior pharyngealconstrictor

Thyropharyngeus Thyroid lamina and hyoid bone (inferior cornu)

Constrictsthelowerpharynx

Cricopharyngeus Cricoidcartilage(lateralmargin) Recurrentlaryngealn.(CNX)and/or external laryngealn.

Sphincter at intersection of laryngopharynxandesophagus

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Superior pharyngeal constrictor

Digastric muscle,anterior belly

Sternohyoid

Thyrohyoid

Esophagus



HyoglossusMylohyoid

Stylopharyngeus

Digastric muscle, posterior belly

Stylohyoid

Styloglossus

Levatorveli palatini

Tensorveli palatini

CricothyroidStraight part

Oblique part

A

Buccinator

Pharyngobasilarfascia

Thyrohyoid membrane

Trachea


Tensor velipalatini

Straightpart

Obliquepart

Trachea Esophagus

Cricopharyngeal part

Thyropharyngeal part

Cerato-pharyngeal part

Chondro-pharyngeal part

Glossopharyngeal part

Mylopharyngeal part

Buccopharyngeal part

Pterygopharyngeal part

Superior pharyngeal constrictor


Crico-thyroid

B

Hyoid bone


2nd gap

3rd gap

4th gap

1st gap

Table 9.14 Pharyngeal gaps

Gap Transmitted structures

1stgap Pharyngotympanictube


2ndgap Stylopharyngeus(insertsonlarynx)

Glossopharyngealn.(CNIX)

3rdgap Internallaryngealn.

Superiorlaryngeala.andv.

4thgap Recurrentlaryngealn.

Inferiorlaryngeala.

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Muscles of the Pharynx

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Stylohyoid

Stylopharyngeus

Thyropharyngeus (inferior pharyngeal constrictor)


Masseter muscle, superficial part

Medial pterygoid

Masseter muscle, deep part

Digastricmuscle,

posteriorbelly

Superiorpharyngealconstrictor

Thyroid gland

Pharyngobasilar fascia

Pharyngealraphe

Hyoid bone,greater horn

C

Cricopharyngeus (inferiorpharyngeal constrictor)

Esophagus

Laimertriangle

Fundiform part

Oblique part

A

Killiantriangle

(dehiscence)

Cricopharyngeus

BZenker diverticulum

Fundiform part of crico-pharyngeus

Vomer

Medial plate of pterygoid process

Foramenlacerum

Foramenovale

Body ofsphenoid bone

Carotid canal

Fig. 9.56 Pharyngeal musculatureLeft lateral (A) and posterior (C) view of the pharyngeal muscles. B Left lateral view of pharyngealconstrictors.Thepharynxisamus-cular tube composed of three pharyngeal con-strictors (Table 9.13) and three longitudinalpharyngeal elevators (Table 9.12). The striated muscles of the pharynx attach to the skull base andpharyngealrapheandarecontinuouswiththeesophagusatthelevelofthecricoidcarti-lage(C6vertebralbody).Thecricopharyngeusis continuous across the midline and acts as a pharyngeal sphincter. When the constrictorsarerelaxed, it isconstrictedandviceversa. Ittherefore has a separate innervation (recur-rentlaryngealnerveand/orexternallaryngealnerve,andgenerallynotpharyngealplexus).

Fig. 9.58 Development of diverticulaA Posteriorview.B Leftlateralview.Thecricopharyngealpartoftheinferior pharyngeal constrictor is divided into an oblique and a fun-diform part. Between them is an area ofmuscular weakness knownas theKillian triangle (or dehiscence). Thisweak spotmay allow themucosaofthehypopharynxtobulgeoutwardthroughthefundiformpart (B), producing a saclike protrusion (Zenker or pharyngoesopha-gealdiverticulum).Thecollectionof food residuesmaygraduallyex-pandthesac,increasingtheriskofobstructingtheesophageallumen.Zenkerdiverticulaaremostcommoninmiddle-agedandelderlyindi-viduals.Symptomsincludetheregurgitationoftrappedfoodresidues.Inolderpatientswhoarenotoptimal surgicalcandidates, treatmentconsistsofdividing the fundiformpartof the inferior constrictoren-doscopically. Note:Diverticulathatdevelop intheLaimertriangleareconsiderably rarer.

Fig. 9.57 Pharyngobasilar fascia at the base of the skull Inferiorview.Thepharyngealmusculaturearisesfromthebaseoftheskull by a thick sheet of connective tissue, the pharyngobasilar fas-cia (shown inred).Thepharyngobasilar fasciaensuresthatthenaso-pharynx is always open.

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Genioglossus

Geniohyoid

Hyoid bone

Thyrohyoid ligament

Thyroid gland

Vocal fold

Vestibular fold

Palatoglossalarch

Uvula Dens of axis (C2)

Soft palate Anterior arch of atlas (C1)

Salpingopharyngeal fold with lateral lymphatic band

Pharyngeal orifice of pharyngotympanic tube

Pharyngeal tonsil in nasopharynx

Torus tubarius with lymphatic tissue (tonsilla tubaria)

Palatine tonsil in oropharynx

Lingual tonsil (on postsulcalportion of the tongue)

Right choana

Cricoid cartilage

Epiglottis

Trachea

Frontal sinus

Nasal septum

Sphenoid sinus

Vallecula

Laryngopharynx

Esophagus

A

Mylohyoid

Naso-pharynx

Oro-pharynx

Laryngo-pharynx

Airway

Foodway

B

Table 9.15 Pharyngeal levels

Region Level Borders

Nasopharynx C1 Roof(sphenoidandoccipitalbones),choanae,andsoftpalate

Oropharynx C2–C3 Uvula,palatoglossalarch,andepiglottis

Laryngopharynx C4–C6 Epiglottis,laryngealinlet,andcricoidcartilage(inferiorborder)

Fig. 9.59 Topography of the pharynxMidsagittalsection,leftlateralview.Thepharynxcommunicateswiththenasalcavity,tympaniccavity,oralcavity,larynx,andesophagus.Itsthreeanteriorcommunicationsdivideitintothreeparts:nasopharynx,oropharynx,andlaryngopharynx(seeTable 9.15). The extensive com-munications make the spread of bacteria from the pharynx a real and dangerouspossibility.Theinflowportions(junctionswiththenasalandoralcavities)arethereforelinedwithlymphatictissue(Waldeyer’sring;see Fig. 9.49). This defense system includes:

• Pharyngealtonsil(ontheroofofthenasopharynx)• Pairedpalatinetonsils(betweenthepalatoglossalandpalatopharyn-

gealarchesoftheoropharynx)• Lingualtonsils(coveringthepostsulcalportionofthetongue)• Pairedtonsillatubaria(aroundthepharyngealorificeofthepharyn-

gotympanictube)withtheirinferiorextensionsalongthesalpingo-pharyngealfolds(lateralbands)

Swellingofthetonsillatubariamayoccludethepharyngealorificeofthe pharyngotympanic(auditory)tube,preventingtheequalizingofpres-sureinthemiddleear.Themobilityofthetympaniccavityisrestricted,resultinginmildhearingloss.Note:Enlargementofthepharyngealton-sil(e.g.,polyps insmallchildren)mayalsoobstructtheorificeofthepharyngotympanictube.

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Pharynx: Topography & Innervation

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To thalamus and cortex (medial lemniscus)

To nucleus of reticular formation (gag and swallowing reflex)

Sensation (pain,temperature, touch)

From the ear(tympanic nerve)

Spinal nucleusof trigeminal nerve

(CN V)

Sensation

Taste

Pharyngeal constrictor

Stylo-pharyngeus

Vagus nerve (CN X)

Superior and inferiorganglia

Nucleus ambiguus

Solitary nucleusPrincipal sensory (pontine) nucleus

of trigeminal nerve (CN V)

Mesencephalic nucleusof trigeminal nerve (CN V)

Special visceral sensory

General somatic sensory

Branchiomotor

Corticonucleartract

IX

X

Glossopharyngeal nerve (CN IX)

Direct motor branchto stylopharyngeus

Pharyngeal plexus

General visceral sensory

A

Oral floorThyroid cartilage

Cricoid cartilage

Epiglottic cartilage

Thyrohyoid

Hyoid bone

Soft palate

Oralfloor Thyroid

cartilage

Cricoid cartilage

Epiglottic cartilage

Passavant ridge (contracted superior pharyngeal constrictor)

B

Thyrohyoid

Hyoid bone

Softpalate

Esophagus

Fig. 9.61 Pharyngeal plexusThepharynxreceivessensoryandmotorinnervationviathepharyngealplexus,formedbyboththeglossopharyngeal(CNIX)andvagus(CNX)nerves,alongwithpostganglionicsympatheticfibersfromthesuperiorcervicalganglion.Note:Onlythevagusnervecontributesmotorfiberstotheplexus(thestylopharyngeusissupplieddirectlybyCNIX).

Fig. 9.60 SwallowingThe larynx,partof theairway, is locatedatthe inlet tothedigestivetract.During swallowing, theairwaymustbeoccluded tokeep foodfromenteringthe larynxandthetrachea(preventingchoking).Swal-lowingconsistsofthreephases:

1.Oralstage(voluntaryinitiation):Thelingualmusclesmovethefoodbolus to theoropharyngeal isthmus,whichfirstexpandsandthencontracts.

2.Pharyngealstage(reflexclosureofairway):Thelongitudinalpharyn-gealmuscleselevatethelarynx.Thelowerairway(laryngealinlet)iscoveredbytheepiglottis.Meanwhile,thesoftpalateistensedandelevatedagainsttheposteriorpharyngealwall,sealingofftheupperairway.

3.Pharyngoesophagealstage(reflextransport):Theconstrictorsmovethe food bolus to the stomach.

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Buccinator

Parotid duct

Masseter

Facial arteryand vein

Submandibulargland

Sternocleido-mastoid

Parotid gland

Accessoryparotid gland

A

Sublingualfold

Genioglossus

Geniohyoid

Mylohyoid

Hyoid boneLingual artery

Submandib-ular gland,intraoral lobe

Submandib-ular duct

Sublingualgland

Oral mucosa

Sublingualpapilla

B Stylohyoid

Hyoglossus

Submandibular gland,extraoral lobe

Fig. 9.62 Major salivary glandsA Left lateral view. B Superior view. There arethreemajor(large,paired)salivaryglands:parotid,submandibular,andsublingual.Theycollectivelyproduce0.5to2.0 litersofsalivaperday,excretedintotheoralcavityviaexcre-tory ducts. The saliva keeps the oral mucosa moist. It also has digestive and protectivefunctions: saliva contains the starch-splittingenzyme amylase and the bactericidal enzyme lysozyme.

1.Parotidglands:Purelyserousglands(watery secretions). The parotid duct crosses super-ficialtothemasseter,piercesthebuccinator, and opens into the oral vestibule opposite the second upper molar.

2. Submandibular glands: Mixed seromucousgland.Thesubmandibularductopensonthesublingualpapillabehindthelowerincisors.

3. Sublingual glands: Predominantly mucous-secreting gland (mucoserous). The sublin-gualglandhasmanysmallerexcretoryductsthatopenonthesublingualfoldorintothesubmandibular duct.

218


Salivary Glands

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Pharyngealglands

Palatineglands

Labialglands

Submandibulargland

Lymph node

Sublingualgland

Parotid gland,superficial

part

Parotidplexus

Parotid gland,deep part

Sternocleido-mastoid

Facial nerve

Superficial temporalartery and vein

Submandib-ular lymphnodes

Hypoglossalnerve

Jugularlymph nodes

Internaljugular vein

Parotidtumor

Facial nerve

Intraparotidlymph nodes

Fig. 9.63 Minor salivary glandsInadditiontothethreemajorpairedglands,700to1000minorglandssecretesalivaintotheoralcavity.Theyproduceonly5to8percentofthe total output, but this amount suffices to keep themouthmoistwhenthemajorsalivaryglandsarenotfunctioning.

Fig. 9.64 Bimanual examination of the salivary glandsThetwosalivaryglandsofthemandible,thesubmandibularglandandsublingualgland,andtheadjacent lymphnodesaregroupedaroundthemobileoralfloorandthereforemustbepalpatedagainstresistance. This is done with bimanual examination.

Fig. 9.65 Spread of malignant parotid tumorsMalignanttumorsoftheparotidglandmayinvadesurroundingstruc-turesdirectly(whitearrowheads)orindirectlyviaregionallymphnodes(red arrowheads). They may also spread systematically (metastasize) throughthevascularsystem.

Fig. 9.66 Intraglandular course of the facial nerve in the parotid gland

Thefacialnervedividesintobrancheswithintheparotidglandandisvulnerableduringthesurgicalremovalofparotidtumors.Topreservethe facial nerve during parotidectomy, it is first necessary to locateandidentifythefacialnervetrunk.Thebestlandmarkforlocatingthenervetrunkisthetipofthecartilaginousauditorycanal.

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Anteriorlingual glands

Apex of tongue

B

Submandibularduct

Lingual nerve

Deep lingualartery and vein

Frenulum

Sublingualfold

Sublingualpapilla

Deep lingualartery

Sublingualartery

Mandible

Submental arteryand vein (from

facial artery and vein)

Hyoid bone

Submandibular ganglion

Lingual arteryand vein

Hypoglossal nerve

Glossopharyngeal nerve

StyloidprocessLingual nerve

A

Dorsal lingual artery

C1 fibers to thyrohyoid

Sublingualvein

Deep lingual vein

Hyoglossus

Thyrohyoid membrane

Fig. 9.67 Nerves and vessels of the tongueA Left lateral view. B Viewoftheinferiorsur-faceofthetongue.The tongue is supplied by the lingual artery (from the maxillary artery), which dividesinto its terminal branches, the deep lingualarteryandthesublingualartery.Thelingualvein usually runs parallel to the artery but on themedialsurfaceofthehyoglossusmuscleand drains into the internal jugular vein. The anteriortwothirdsofthelingualmucosare-ceives its somatosensory innervation (sensi-tivity to thermal and tactile stimuli) from the lingual nerve,whichisabranchofthetrigem-inalnerve’smandibulardivision(CNV3). The lingualnervetransmitsfibersfromthechordatympaniof the facialnerve(CNVII),amongthem the afferent taste fibers for the anterior two thirds of the tongue. The chorda tym-pani also contains presynaptic, parasympa-thetic visceromotor axons that synapse in thesubmandibularganglion,whoseneuronsin turn innervate the submandibular and sublingualglands.Thepalatoglossusreceivesits somatomotor innervation fromthevagusnerve (CNX)via thepharyngealplexus, theother lingual muscles from the hypoglossalnerve(CNXII).

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Neurovasculature of the Tongue

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Vagus nerve (CN X)

Glossopharyngealnerve (CN IX)

Facial nerve (CN VII via chorda tympani)

Lingual nerve(mandibular nerve, CN V3)

Glossopharyngealnerve (CN IX)

Vagus nerve (CN X)

Taste Somatic sensation

BA

Submentallymph nodes

Submandibularlymph nodes

Internaljugular vein

Jugulofacialvenous junction

Deep cervicallymph nodes

Jugularlymph nodes

Lingual vein

Fig. 9.68 Innervation of the tongueAnteriorview.Leftside:Somatosensoryinnervation.Rightside:Tasteinnervation.The posterior one third of the tongue (postsulcal part) primarily re-ceivessomatosensoryandtasteinnervationfromtheglossopharyngealnerve(CNIX),withadditionaltastesensationconveyedbythevagus

Fig. 9.69 Lymphatic drainage of the tongue and oral floorA Left lateral view. B Anterior view.The lymphatic drainage of the tongue and oral floor ismediated bysubmentalandsubmandibulargroupsoflymphnodesthatultimatelydrain intothe lymphnodesalongthe internal jugularvein(A,jugular

lymphnodes).Because the lymphnodes receivedrainage fromboththe ipsilateral and contralateral sides (B), tumor cells may becomewidelydisseminatedinthisregion(e.g.,metastaticsquamouscellcar-cinoma,especiallyonthelateralborderofthetongue,frequentlyme-tastasizes to the opposite side).

nerve(CNX).Theanteriortwothirdsofthetongue(presulcalpart)re-ceivesitssomatosensoryinnervation(e.g.,touch,pain,andtempera-ture)fromthelingualnerve(branchofCNV3) and its taste sensation from the chorda tympani branchof the facial nerve (CNVII).Distur-bancesofsensation inthepresulcaltonguecanthereforebeusedtodeterminefacialortrigeminalnervelesions.

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Postcentralgyrus

Insula

Solitary tract nucleus

Epiglottis

Chordatympani

Vagus nerve

Glossopharyngealnerve

Geniculate ganglion

Ventral posteromedialnucleus of thalamus

Dorsal tegmentalnucleus

Facial nerve

Medial para-brachial nucleus

Spinal nucleus oftrigeminal nerve

Dorsal vagal nucleus

Gustatory partInferior (petrosal)

ganglion

Dorsal trigemino-thalamic tract

Inferior(nodose)ganglion

Lingual nerve

Oval nucleus

Fig. 9.70 Gustatory pathwayThereceptorsforthesenseoftastearethetastebudsofthetongue(see Fig. 9.71). Unlike other receptor cells, the receptor cells of thetastebudsarespecializedepithelialcells (secondarysensorycells,asthey do not have an axon). When these epithelial cells are chemically stimulated,thebaseofthecellsreleasesglutamate,whichstimulatestheperipheralprocessesofafferentcranialnerves.Thesedifferentcra-nialnervesservedifferentareasofthetongue.Itisrare,therefore,foracompletelossoftaste(ageusia)tooccur.

• Theanterior two thirdsofthetongueissuppliedbythefacialnerve(CNVII),theafferentfibersfirstpassinginthelingualnerve(branchof the trigeminal nerve) and then in the chorda tympani to thegeniculateganglionofthefacialnerve.

• Theposterior third of the tongue and the vallate papillae are supplied bytheglossopharyngealnerve(CNIX).Asmallareaontheposteriorthirdofthetongueisalsosuppliedbythevagusnerve(CNX).

• Theepiglottis and valleculaearesuppliedbythevagusnerve(CNX).

Peripheralprocessesfrompseudounipolarganglioncells(whichcorre-spondtopseudounipolarspinalganglioncells)terminateonthetastebuds. The central portions of these processes convey taste information to thegustatorypartof thenucleusof the solitary tract. Thus, theyfunction as thefirst afferentneuronof thegustatorypathway. Their

perikaryaarelocatedinthegeniculateganglionforthefacialnerve,in theinferior(petrosal)ganglionfortheglossopharyngealnerve,andin the inferior (nodose) ganglion for the vagus nerve. After synapsing inthegustatorypartofthenucleusofthesolitarytract,theaxonsfromthe second neuron are believed to terminate in the medial parabrachial nucleus,wheretheyarerelayedtothethirdneuron.Mostoftheaxonsfrom the third neuron cross to the opposite side and pass in the dorsal trigeminothalamictracttothecontralateralventralposteromedialnu-cleus of the thalamus. Some of the axons travel uncrossed in the same structures.Thefourthneuronsofthegustatorypathway,locatedinthethalamus,project to thepostcentralgyrusand insular cortex,wherethefifthneuron is located.Collaterals fromthefirstandsecondneu-ronsofthegustatoryafferentpathwayaredistributedtothesuperiorand inferior salivatorynuclei. Afferex impulses in these fibers inducethesecretionofsalivaduringeating(“salivaryreflex”).Theparasympa-theticpreganglionicfibersexitthebrainstemviacranialnervesVIIandIX(seethedescriptionsofthesecranialnervesfordetails).Besidesthispurely gustatorypathway, spicy foodsmay also stimulate trigeminalfibers(notshown),whichcontributetothesensationoftaste.Finally,olfaction(thesenseofsmell),too,isamajorcomponentofthesenseof taste as it is subjectively perceived: patients who cannot smell (anos-mosia) report that their food tastes abnormally bland.

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Gustatory System

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Foramencecum

Foliatepapillae (D)

Fungiformpapillae (C)

Vallatepapilla (B)

Terminalsulcus

A

Epiglottis

Vallecula

Medianglossoepiglottic fold

Lateralglossoepiglotticfold

Seromucousglands

Taste bud

B

C

Taste bud

Taste bud

D

Tastepore

Nonkeratinizedsquamous epithelium

Nerve Basal cellDark taste cell

Lighttaste cell

Fig. 9.72 Microscopic structure of a taste budNerves induce the formation of taste buds in the oral mucosa. Axons of cranial nerves VII, IX, and X grow into the oralmucosa from thebasalsideandinducetheepitheliumtodifferentiateintothelightanddark taste cells (=modified epithelial cells). Both types of taste cellhavemicrovillithatextendtothegustatorypore.Forsweetandsalty,the taste cell is stimulated by hydrogen ions and other cations. Theother tastequalities aremediatedby receptorproteins towhich thelow-molecular-weightflavoredsubstancesbind(detailsmaybefoundintextbooksofphysiology).Whenthe low-molecular-weightflavoredsubstancesbindtothereceptorproteins,theyinducesignaltransduc-tionthatcausesthereleaseofglutamate,whichexcitestheperipheralprocesses of the pseudounipolar neurons of the three cranial nerve ganglia.Thetastecellshavealifespanofapproximately12daysandregeneratefromcellsatthebaseofthetastebuds,whichdifferentiateinto new taste cells.

Note:Theoldnotionthatparticularareasofthetonguearesensitivetospecifictastequalitieshasbeenfoundtobefalse.

Fig. 9.71 Organization of the taste receptors in the tongueThehumantonguecontainsapproximately4600tastebuds inwhichthe secondary sensory cells for taste perception are collected. The tastebudsareembeddedintheepitheliumofthelingualmucosaandarelocatedonthesurfaceexpansionsofthelingualmucosa—theval-latepapillae(principalsite,B),thefungiformpapillae(C),andthefo-liate papillae (D).Additionally, isolated tastebuds are located in the

mucousmembranesofthesoftpalateandpharynx.Thesurroundingserousglandsofthetongue(Ebnerglands),whicharemostcloselyas-sociatedwiththevallatepapillae,constantlywashthetastebudscleantoallowfornewtasting.Humanscanperceivefivebasictastequalities:sweet, sour, salty, bitter, and a fifth “savory” quality, called umami,whichisactivatedbyglutamate(atasteenhancer).

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head and neck anatomy for dental medicine

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