head and neck anatomy for dental medicine
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Selections from chapter 9: Oral Cavity & Perioral Regions from the Head and Neck Anatomy for Dental MedicineTRANSCRIPT
Head and Neck Anatomyfor Dental Medicine
Schuenke / SchulteSchum
acherH
ead and Neck Anatomy
for Dental Medicine
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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.
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ISBN 978-1-60406-209-0
Michael SchuenkeErik SchulteUdo Schumacher
Consulting EditorEric Baker
Illustrations byMarkus VollKarl Wesker
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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).
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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.
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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.
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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).
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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.
Tooth Crown Surfaces Root(s)
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.
Tooth Crown Surfaces Root(s)
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
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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.
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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
Deciduouslateral incisor
Secondpermanent molar
First permanentmolar
Second permanentpremolar
First permanentpremolar
Permanentcanine
Permanentlateral incisor
Permanentcentral incisor
D
First per-manent molar
Second decid-uous molar
First deciduousmolar
Deciduouscanine
Deciduouslateral incisor
Deciduouscentral incisor
Second per-manent molar
Second per-manent premolar
Mentalforamen
First permanent premolar
Permanentcanine
Permanentlateral incisor
Permanentcentral incisor
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
Permanentlateral incisor
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.
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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
Transversepalatine suture
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
Transversepalatine suture
Pterygoidcanal
Septum ofsphenoid sinus
Opticcanal
Anteriorclinoid process
Superior orbital fissure
Inferiororbital fissure
Choana
Medianpalatine suture
Incisiveforamen Palatine process of maxilla
Pterygoid process,medial plate
Pterygoid process,lateral plate
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
Head (condyle) of mandible
B
Lingula
Submandibularfossa
Superior andinferior genial (mental) spines
Digastricfossa
Mylohyoidgroove
C
Angle
Obliqueline
Mentalforamen
Alveolarpart
Mentaltubercle
Mandibularforamen
Mandibularnotch
Coronoidprocess
Ramusof mandible
Pterygoid fovea
Head (condyle) of mandible
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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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
Head (condyle)of mandible
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.
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Pterygoid process,medial plate
Pterygoid process,lateral plate
Stylomandibularligament
Sphenomandib-ular ligament
Mandibularnotch
Pterygospinousligament
Joint capsule
Stylomandibular ligament
Head (condyle)of mandible
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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Lateral pterygoid muscle, inferior head
Head of mandible
Joint capsule
Articular disk
Articulartubercle
Lateral pterygoid muscle,superior head
A
Mandibular fossa
Lateral pterygoid muscle, inferior head
Joint capsule
Head of mandible
Lateral pterygoid muscle,superior head
B
Articular disk
Axis of rotation15°
Lateral pterygoid muscle, inferior head
Joint capsule
Articular disk
Lateral pterygoid muscle,superior head
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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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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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
Muscle Origin Insertion Innervation Action
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).
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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
Muscle Origin Insertion Innervation Action
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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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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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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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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Tensor velipalatini
Circular muscle fibers of esophagus
Posterior cricoarytenoid
Transverse arytenoid
Middle pharyngeal constrictor
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
Inferior pharyngeal constrictor
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
Levator velipalatini
Pharyngeal tonsil
Uvula
Tubal orifice
Cartilaginous part of pharyngotympanic (auditory) tube
Medial plate of pterygoid process(sphenoid bone)
Pterygoidhamulus
Tensor veli palatini
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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Table 9.12 Muscles of the soft palate and pharyngeal elevators
Muscle Origin Insertion Innervation Action
Tensor veli palatini
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.
Levator veli palatini
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
Muscle Origin Insertion Innervation Action
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
Inferior pharyngeal constrictor
Middle pharyngeal constrictor
HyoglossusMylohyoid
Stylopharyngeus
Digastric muscle, posterior belly
Stylohyoid
Styloglossus
Levatorveli palatini
Tensorveli palatini
CricothyroidStraight part
Oblique part
A
Buccinator
Pharyngobasilarfascia
Thyrohyoid membrane
Trachea
Levator velipalatini
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
Middle pharyngeal constrictor
Crico-thyroid
B
Hyoid bone
Inferior pharyngeal constrictor
2nd gap
3rd gap
4th gap
1st gap
Table 9.14 Pharyngeal gaps
Gap Transmitted structures
1stgap Pharyngotympanictube
Levator veli palatini
2ndgap Stylopharyngeus(insertsonlarynx)
Glossopharyngealn.(CNIX)
3rdgap Internallaryngealn.
Superiorlaryngeala.andv.
4thgap Recurrentlaryngealn.
Inferiorlaryngeala.
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Stylohyoid
Stylopharyngeus
Thyropharyngeus (inferior pharyngeal constrictor)
Middle 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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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.
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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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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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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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