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ANATOMY OF THE NECK. Kaan Yücel M.D., Ph.D . 24. October . 2011 Monday. The neck is the transitional area between the base of the cranium superiorly and the clavicles inferiorly .

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slide1

ANATOMY OF THE NECK

Kaan Yücel M.D., Ph.D.

24. October. 2011Monday

slide2

Theneck is thetransitionalareabetweenthebase of thecraniumsuperiorlyandtheclaviclesinferiorly.

  • Neck is a passagewayformanyimportantstructuresextendingbetweentheheadandthetrunksuch as thelarynxandthethyroidandparathyroidglands.
slide3

Theneck is relativelyslendertoallowtheflexibilitynecessarytopositiontheheadtomaximizetheefficiency of itssensoryorgans (mainlytheeyeballs but alsotheears, mouth, andnose).

  • Thusmanyimportantstructuresarecrowdedtogether in theneck, such as muscles, glands, arteries, veins, nerves, lymphatics, trachea, esophagus, andvertebrae.
  • Consequently, theneck is a well-knownregion of vulnerability.
slide4

Themainarterialbloodflowtotheheadandneck (thecarotidarteries) andtheprincipalvenousdrainage (thejugularveins) lieanterolaterally in theneck.

  • Carotid/jugularbloodvesselsarethemajorstructurescommonlyinjured in penetratingwounds of theneck.
slide5

Thebrachialplexuses of nervesoriginate in theneckandpassinferolaterallytoentertheaxillaeandcontinueintoandsupplytheupperlimbs.

slide6

Bones of theNeck

  • Theskeleton of theneck is formedbythecervicalvertebrae, hyoid bone, manubrium of thesternum, andclavicles.
  • Thesebonesareparts of theaxialskeletonexcepttheclavicles, whicharepart of theappendicularskeleton.
slide7

CervicalVertebrae

  • 7 cervicalvertebrae form thecervicalregion of thevertebralcolumn, whichenclosesthespinalcordandmeninges.
  • Thecentrallyplacedvertebralbodies
  • Supportthehead, andtheintervertebral (IV) articulations
  • especiallythecraniovertebraljoints at itssuperiorend
  • Providetheflexibilitynecessarytoallowpositioning of thehead.
slide8

HyoidBone (Hyoid)

Liesin theanteriorpart of theneck at thelevel of the C3 in theanglebetweenthemandibleandthethyroidcartilage.

Suspendedbymusclesthatconnect it tothemandible, styloidprocesses, thyroidcartilage, manubrium, andscapulae.

Doesnot articulatewithanyother bone.

slide9

It is suspendedfromthestyloidprocesses of thetemporalbonesbythestylohyoidligamentsand is firmlyboundtothethyroidcartilage.

slide10

The hyoid consists of a body and greater and lesser horns (L. cornua; the lesser horn is the attachment for the sytlohyoid ligament.).

Functionally, the hyoid serves as an attachment for anterior neck muscles and a prop to keep the airway open.

slide11

Fascia of theNeck

Structuresin theneckaresurroundedby a layer of subcutaneoustissue (superficialfascia) andarecompartmentalizedbylayers of deepcervicalfascia.

The knowledge of the organization of the cervical fascia is critical in figuring out where the infections of this region may spread.

slide12

Superficial cervical fascia

Layerof fattyconnectivetissuethatliesbetweenthedermis of the skin andtheinvestinglayer of deepcervicalfascia. Thistissue is usuallythinnerthan in otherregions, especiallyanteriorly.

Containscutaneousnerves, bloodandlymphaticvessels, superficiallymphnodes, andvariableamounts of fat. Anterolaterally, it containstheplatysma.

slide13

Theplatysma (G. flatplate) is a broad, thinsheet of muscle in thesubcutaneoustissue of theneck.

Theexternaljugularvein (EJV) andthe main cutaneousnerves of theneckaredeeptotheplatysma.

Theplatysmacoverstheanterolateralaspect of theneck.

slide14

Actingfromitssuperiorattachment, theplatysmatensesthe skin, producingvertical skin ridgesandreleasingpressure on thesuperficialveins.

Actingfromitsinferiorattachment, theplatysmahelpsdepressthemandibleanddrawthecorners of themouthinferiorly.

slide15

As a muscle of facialexpression, theplatysmaservestoconveytensionorstress.

Theplatysma is suppliedbythecervicalbranch of CN VII.

slide16

Deepcervicalfascia

Thedeepcervicalfasciaconsists of threefasciallayers (sheaths): investing, pretracheal, andprevertebrallayerssupporttheviscera (e.g., thethyroidgland), muscles, vessels, anddeeplymphnodes.

Thedeepcervicalfasciaalsocondensesaroundthecommoncarotidarteries, internaljugularveins (IJVs), andvagusnervesto form thecarotidsheath.

slide17

Investinglayer of deepcervicalfascia

Mostsuperficialdeepfasciallayer,

Surroundstheentireneckdeeptothe skin andsubcutaneoustissue.

Anteriorly, surroundstheinfrahyoidmuscles.

slide18

Theinvestingfascia is attached:

  • Superiorlytotheexternaloccipitalprotuberanceandthesuperiornuchalline;
  • Laterallytothemastoidprocessandzygomaticarch; and
  • Inferiorlytothespine of thescapula, theacromion, theclavicle, andthemanubrium of sternum.
slide19

Pretracheallayer of deepcervicalfascia

Extendsbetween the hyoid bone and thorax.

At the thorax blends with the fibrous pericardium.

Has twolayers:

Muscularlayerenclosestheinfrahyoidmuscles

Viscerallayerencloses the thyroid gland, trachea and esophagus.

slide21

Posteriorly, thepretracheallayer is referredto as thebuccopharyngealfascia(a fascia enclosing the pharynx, superior continuation of the fascia covering the buccinator muscle) andseparatesthepharynxandtheesophagusfromtheprevertebrallayer.

slide22

Thebuccopharyngealfasciabeginssuperiorly at thebase of theskullandendsinferiorly in thethoraciccavity.

Laterally, it blends with the carotid sheath.

slide23

Prevertebrallayer of deepcervicalfascia

Forms a tubularsheathforthevertebralcolumnandthemusclesassociatedwith it.

Extendsbetweenthebase of theskulland T3 vertebra.

Attached posteriorlyalongthelength of theligamentumnuchae, andsuperiorlyforms a continuouscircularlineattachingtothebase of theskull.

slide24

The prevertebral layer of deep fascia is fixed to the cranial base superiorly.

Infero-laterally it extends to axilla and continuous with the axillary sheath enclosing the axillary vessels and the brachial plexus.

slide26

CarotidSheath

  • Tubularfascialinvestment;extendsfromthecranialbasetotheroot of theneck.
  • Contains :
  • Commonandinternalcarotidarteries.
  • Internaljugularvein.
  • Vagusnerve (CN X).
  • Somedeepcervicallymphnodes.
  • Carotidsinusnerve.
  • Sympatheticnervefibers (carotidperiarterialplexuses)
slide27

Thecarotidsheathandpretrachealfasciacommunicatefreelywiththemediastinum of thethoraxinferiorlyandthecranialcavitysuperiorly.

  • Thesecommunicationsrepresentpotentialpathwaysforthe spread of infectionandextravasatedblood.
slide28

Fascial spaces

Between the fascial layers in the neck are spaces that may provide a conduit for the spread of infections from the neck to the mediastinum.

Three spaces could be involved in this process:

Pretrachealspace between the investing layer of cervical fascia and the pretrachealfascia,which passes between the neck and the anterior part of the superior mediastinum;

Retropharyngealspace

Withinthe prevertebral layer covering the anterior surface of the transverse processes and bodies of the cervical vertebrae.

slide29

Retropharyngealspace

Largestandmostimportantinterfascialspace in theneck.

Potentialspacethatconsists of looseconnectivetissuebetweenthevisceralpart of theprevertebrallayer of deepcervicalfasciaandthebuccopharyngealfasciasurroundingthepharynxsuperficially.

slide30

Itpermitsthemovement of pharynx, larynxandesophagus

  • Theretropharyngealspace is closedwiththeskullbasesuperiorlyandthecarotidsheathlaterally.
  • Itextendsfromthebase of theskulltotheupperpart of theposteriormediastinum.
slide32

CervicalRegions

Toallowclearcommunicationregardingthelocation of structures, injuries, orpathologies, theneck is dividedintoregions.

Betweenthecranium (mandibleanteriorlyandoccipital bone posteriorly) andtheclavicles, theneck is dividedinto4 majorregions.

Basedon theusuallyvisibleand/orpalpableborders of thelargeandrelativelysuperficialSCMandtrapeziusmuscles.

slide33

SternocleidomastoidRegion

  • Thesternocleidomastoid (SCM) muscle is a keymuscularlandmark in theneck, formingthesternocleidomastoidregion [1].
  • TheSCM visiblydivideseachside of theneckintotheanterior [2] andlateralcervical[3] regions(anteriorandposteriortriangles).

2

1

3

slide34

The SCM is a broad, strap-likemusclethat has twoheads:

Sternalheadattachestothemanubrium

Clavicularheadattachestotheclavicle

slide35

TheSCMsproducemovement at thecraniovertebraljoints, thecervicalintervertebraljoints, or at both.

Thecranialattachments of theSCMslieposteriortotheaxis of theatlanto-occipital (AO) joints.

Bilateralcontraction of theSCMswillcauseextension of thehead at the AO joints, elevatingthechin

Actingbilaterally, theSCMs can alsoflextheneck.

slide36

PosteriorCervicalRegion

  • Theregionposteriortotheanteriorborders of (i.e., correspondingtothearea of) thetrapezius is theposteriorcervicalregion.
  • Thesuboccipitalregion is deeptothesuperiorpart of thisregion.
  • Thetrapezius is a large, flattriangularmusclethatcoverstheposterolateralaspect of theneckandthorax.
slide37

Thetrapezius is a:

  • Superficialmuscle of theback
  • Posterioraxioappendicularmuscle, thatacts on thepectoralgirdle
  • Cervicalmuscle, that can producemovement of thecranium.
  • Thetrapeziusattachesthepectoralgirdletothecraniumandthevertebralcolumnandassists in suspending it.
slide38

LateralCervicalRegion

  • Thelateralcervicalregion (posteriortriangle) is bounded:
  • Anteriorlybytheposteriorborder of the SCM.
  • Posteriorlybytheanteriorborder of thetrapezius.
  • Inferiorlybythemiddlethird of theclaviclebetweenthetrapeziusandthe SCM.
slide39

Muscles in theLateralCervicalRegion

Thefloor of thelateralcervicalregion is usuallyformedbytheprevertebralfasciaoverlyingfourmuscles: spleniuscapitis, levatorscapulae, middlescalene(L. scalenusmedius), andposteriorscalene(L. scalenusposterior).

slide40

Nerves of theLateralCervicalRegion

Thespinalaccessorynerve (CN XI) passesdeeptothe SCM, supplying it beforeenteringthelateralcervicalregion at orinferiortothejunction of thesuperiorandmiddlethirds of theposteriorborder of the SCM.

slide41

Theroots of thebrachialplexus (anterior rami of C5-C8 and T1)appearbetweentheanteriorandthemiddlescalenemuscles.

  • Thefive rami uniteto form thethreetrunks of thebrachialplexus, whichdescendinferolaterallythroughthelateralcervicalregion.
  • Theplexusthenenterstheaxilla, providinginnervationformost of theupperlimb.
slide42

Vesselsin the

LateralCervicalRegion

Thelateralbranches of thethyrocervicaltrunk

Thethirdpart of thesubclavianartery

Partof theoccipitalartery

slide43

Veins in lateralcervicalregion

Theexternaljugularvein (EJV) is formedbytheunion of theposteriordivision of theretromandibularveinwiththeposteriorauricularvein.

slide44

TheEJVterminates in anddrainsintothesubclavianvein.

  • Thesubclavianvein, themajorvenouschanneldrainingtheupperlimbuniteswiththeIJVto form thebrachiocephalicvein.
slide45

Lymphnodes in theLateralCervicalRegion

  • Lymphfromsuperficialtissues in thelateralcervicalregionentersthesuperficialcervicallymphnodes.
  • Efferentvesselsfromthesenodesdrainintothedeepcervicallymphnodes, which form a chainembedded in thefascia of thecarotidsheath.
slide46

AnteriorCervicalRegion

  • Theanteriorcervicalregion (anteriortriangle) has thefollowing:
  • An anteriorboundaryformedbythemedianline of theneck.
  • A posteriorboundaryformedbytheanteriorborder of the SCM.
  • A superiorboundaryformedbytheinferiorborder of themandible.
  • An apexlocated at thejugularnotch in themanubrium.
  • A roofformedbysubcutaneoustissuecontainingtheplatysma.
  • A floorformedbythepharynx, larynx, andthyroidgland.
slide47

Formorepreciselocalization of structures, theanteriorcervicalregion is subdividedintofoursmallertrianglesbythedigastricandomohyoidmuscles: theunpairedsubmentaltriangle (smen)andthreesmallpairedtriangles—submandibular(sm), carotid (car), andmuscular (mus).

slide48

Submentaltriangle

  • Inferiortothechin
  • A suprahyoidareaboundedinferiorlybythe body of thehyoidandlaterallybytherightandleftanteriorbellies of thedigastricmuscles.
  • Containsseveralsmallsubmentallymphnodesandsmallveinsthatuniteto form theanteriorjugularvein.

Anteriordigastricmuscles (abd). Mylohyoidmuscle (mh)

slide49

Submandibulartriangle

  • A glandularareabetweentheinferiorborder of themandibleandtheanteriorandposteriorbellies of thedigastricmuscle.
  • anterior belly of digastric(abd)
  • posterior belly of digastric (pbd)
  • Submandibularlymphnodes
  • Hypoglossalnerve (CN XII)
  • Nervetothemylohyoidmuscle (a branch of CN V3, whichalsosuppliestheanteriorbelly of thedigastric)
  • Partsof thefacialarteryandvein
  • Submentalartery (a branch of thefacialartery)
slide50

Musculartriangle (omotrachealtriangle)

  • Boundedbythesuperiorbelly of theomohyoidmuscle, theanteriorborder of the SCM, andthemedianplane of theneck.

Containstheinfrahyoidmusclesandviscera (e.g., thethyroidandparathyroidglands).

slide51

MUSCLES IN ANTERIOR CERVICAL REGION

Intheanterolateralpart of theneck, thehyoidprovidesattachmentsforthesuprahyoidmusclessuperiorto it andtheinfrahyoidmusclesinferiorto it.

Thesehyoidmusclessteadyormovethehyoidandlarynx. Fordescriptivepurposes, theyaredividedintosuprahyoidandinfrahyoidmuscles.

slide53

Musclesinferiortothehyoidareinfrahyoidmuscles

  • omohyoid (superficialplane)
  • sternohyoid(superficialplane)
  • thyrohyoid (deepplane)
  • sternothyroid (deepplane)
slide55

AnteriorCervicalRegion

Arteries in anteriorcervicalregion

Theanteriorcervicalregioncontainsthecarotidsystem of arteries, consisting of thecommoncarotidarteryandits terminal branches, theinternalandexternalcarotidarteries.

Italsocontainsthe IJV anditstributariesandtheanteriorjugularveins.

slide56

Commoncarotidartery

  • The common carotid artery arises from the brachiocephalic trunk on the right side and from the arch of aorta on the left side.
  • Thecommoncarotidarteryandone of its terminal branches, theexternalcarotidartery, arethe main arterialvessels in thecarotidtriangle.
slide57

Thecarotidtriangle is bounded:

  • posteriorlybythesternocleidomastoideus;
  • inferiorly, bythesuperiorbelly of theomohyoideus
  • superiorly, bythestylohyoideusandtheposteriorbelly of thedigastricus.
slide58

Eachcommoncarotidarteryascendswithinthecarotidsheathwiththe IJV andvagusnervetothelevel of thesuperiorborder of thethyroidcartilage.

  • Here, eachcommoncarotidarteryterminatesbydividingintotheinternalandexternalcarotidarteries.
slide59

Theinternalcarotidartery has nobranches in theneck; theexternalcarotid has several.

  • Therightcommoncarotidarterybegins at thebifurcation of thebrachiocephalictrunk.
  • Therightsubclavianartery is theotherbranch of thistrunk.
  • Fromthearch of the aorta, theleftcommoncarotidarteryascendsintotheneck.
slide60

Theinternalcarotidarteriesaredirectcontinuations of thecommoncarotidssuperiortotheorigin of theexternalcarotidartery, at thelevel of thesuperiorborder of thethyroidcartilage.

slide61

Thecarotid body (carotidglomusorglomuscaroticum) is located in thecleftbetweentheinternalandtheexternalcarotidarteries.

Whilethecarotidbodiescontainchemoreceptors, thecarotidsinus, a slight dilatation of the proximal part of internal carotidartery, containsbaroreceptors. Thecarotidsinus is sensitivetoblood pressure changes.

slide62

Role of thecarotidbodies

  • Carotidbodiesaresensitivetodecreased O2andincreased CO2content of theblood
  • Inbothcasesvisseralreflexesareactivatedleadingtoincreasedventilation (increaseddepthand rate of repiration) and as well as rise of heart rate andbloodpressure
  • Boththeafferentandefferentpathwaysforthisreflex is throughthevagusandglossopharyngealnerves.
slide63

Internalcarotidartery

  • Theinternalcarotidarteriesenterthecraniumthroughthecarotidcanals in thepetrousparts of thetemporalbonesandbecomethe main arteries of thebrainandstructures in theorbits.
  • No namedbranchesarisefromtheinternalcarotidarteries in theneck.
slide64

Theinternalcarotidarterysuppliesthebraintogetherwiththevertebralarterywhich is a branch of thesubclavianartery.

  • Afterenteringthecranialvault it formsthepolygon of Willistogetherwiththevertebralartery.
slide65

Externalcarotidartery

  • Suppliesmoststructuresexternaltothecranium; theorbitandthepart of theforeheadandscalpsuppliedbythesupraorbitalarteryarethemajorexceptions.
  • Extendstothelevel of theparotidgland.Terminatesbydividingintotwobranches, themaxillaryarteryandthesuperficialtemporalarterywithin the tissue of the parotidgland
slide66

Veins in anteriorcervicalregion

  • Mostveins in theanteriorcervicalregionaretributaries of theinternaljugularvein (IJV), typicallythelargestvein in theneck.
  • Internaljugularvein is the main veindrainingtheintracranialveins, as well as theheadandneck.
slide67

Veins in anteriorcervicalregion

Itcommences at thejugularforamen in theposteriorcranial fossa as thedirectcontinuation of thesigmoid sinus.

IJVuniteswiththesubclavianveintofromthebrachiocephalicvein.

slide68

NERVES IN ANTERIOR CERVICAL REGION

Severalnerves, includingbranches of cranialnerves, arelocated in theanteriorcervicalregion.

Transversecervicalnerve (C2 and C3): suppliesthe skin coveringtheanteriorcervicalregion.

slide69

Hypoglossalnerve (CN XII): the motor nerve of thetongue, entersthesubmandibulartriangledeeptotheposteriorbelly of thedigastricmuscletosupplytheintrinsicandfour of thefiveextrinsicmuscles of thetongue.

Thenervegivesoffthesuperiorroot of the ansa cervicalisandthen a branchtothegeniohyoidmuscle.

slide70

Branchesof theglossopharyngeal(CN IX) andvagus(CN X) nerves: in thesubmandibularandcarotidtriangles. CN IX is primarilyrelatedtothetongueandpharynx. Intheneck, CN X givesrisetopharyngeal, laryngeal, andcardiacbranches.

slide71

ROOT OF THE NECK

  • Junctionalareabetweenthethoraxandtheneck.
  • Cervicalside of thesuperiorthoracicaperture, throughwhichpassallstructuresgoingfromthethoraxtotheheadorupperlimbandviceversa.
slide72

Theinferiorboundary of theroot of theneck is thesuperiorthoracicaperture, formedlaterallybythe 1st pair of ribsandtheircostalcartilages, anteriorlybythemanubrium of thesternum, andposteriorlybythe body of T1 vertebra.

slide73

NERVES IN ROOT OF NECK

Therearethreepairs of majornerves in theroot of theneck:

vagusnerves

phrenicnerves

sympathetictrunks

slide74

VagusNerves (CN X)

Afteritsexitfromthejugularforamen, eachvagus

nervepassesinferiorly in theneckwithinthe

posteriorpart of thecarotidsheath in theanglebetweenthe

IJV andthecommoncarotidartery.

slide75

Therightvagusnervepassesanteriortothefirstpart of thesubclavianarteryandposteriortothebrachiocephalicveinandtoenterthethorax.

  • Theleftvagusnervedescendsbetweentheleftcommoncarotidandtheleftsubclavianarteriestoenterthethorax.
slide76

Therecurrentlaryngealnervesarisefromthevagusnerves in theinferiorpart of theneck.

  • Thecardiacbranches of CN X originate in theneck as well as in thethoraxandconveypresynapticparasympatheticandvisceralafferentfiberstothecardiacplexus of nerves.
slide77

PhrenicNerves

  • Thephrenicnervespassundertheprevertebrallayer of deepcervicalfascia, betweenthesubclavianarteriesandveins, andproceedtothethoraxtosupplythediaphragm.
  • Thephrenicnervesareimportantbecause, in additiontotheirsensorydistribution, theyprovidethe sole motor supplytotheirownhalf of thediaphragm.
slide78

SympatheticTrunks

  • Eachsympathetictrunksdescend at theantero-lateralparts of thevertebralcolumn. Sympathetictrunksareformed of sympatheticgangliaandnervefibersextendingbetweenthem.
  • Thecervicalportion of thesympathetictrunksliesanterolateraltothevertebralcolumn, extendingsuperiorlytothelevel of the C1 vertebraorcranialbase.
slide79

Thesympathetictrunksreceive no white rami communicantes in theneck (white rami associatedwithcervicalspinalnerves).

  • Thecervicalportion of thetrunksincludesthreecervicalsympatheticganglia: superior, middle, andinferior.
  • Thesegangliareceivepresynapticfibersconveyedtothetrunkbythesuperiorthoracicspinalnervesandtheirassociatedwhite rami communicantes, whichthenascendthroughthesympathetictrunktotheganglia.
slide81

Aftersynapsingwiththepostsynapticneuron in thecervicalsympatheticganglia, postsynapticneuronssendfiberstothe:

  • Cervicalspinalnervesviagray rami communicantes
  • Thoracicvisceraviacardiopulmonarysplanchnicnerves
  • Headandviscera of theneckviacephalicarterialbranches (rami)
slide82

Root of Neck

  • Arteries in root of neck
  • Thebrachiocephalictrunkis coveredanteriorlybytherightsternohyoidandsternothyroidmuscles; it is thelargestbranch of thearch of the aorta.
  • Itarises in themidlinefromthebeginning of thearch of theaorta.
slide83

Itpassessuperolaterallytotherightwhere it dividesintotherightcommoncarotidandrightsubclavianarteries.

  • Thebrachiocephalictrunkusually has nobranches.
slide84

Subclavian artery

  • Thesubclavianarteriessupplytheupperlimbs; theyalsosendbranchestotheneckandbrain.
  • Therightsubclavianarteryarisesfromthebrachiocephalictrunk.
  • Theleftsubclavianarteryarisesfromthearch of the aorta distaltotheleftcommoncarotidartery.
slide86

Veins in root of neck

Twolargeveinsterminating in theroot of theneckaretheexternaljugularvein (EJV), drainingbloodreceivedmostlyfromthescalpandface, andthevariableanteriorjugularvein (AJV), usuallythesmallest of thejugularveins.

slide88

Thesubclavianvein, thecontinuation of theaxillaryvein, begins at thelateralborder of the 1st ribandendswhen it uniteswiththeinternaljugularvein (IJV).

  • Thesubclavianvein is separatedfromthesubclavianarterybytheanteriorscalenemuscle. Itusually has onlyonenamedtributary, the EJV.
slide90

Theinternaljugularvein (IJV) is the main veindrainingtheintracranialveins, as well as theheadandneck.

  • Itendsposteriorbyunitingwiththesubclavianveinto form thebrachiocephalicvein.
  • Thisunion is commonlyreferredto as thevenousangleand is the site wherethethoracicduct (leftside) andtherightlymphatictrunk (rightside) drainlymphcollectedthroughoutthe body intothevenouscirculation.
slide91

Right andleftbrachiocephalicveinsuniteto form thesuperior vena cava (opensintotherightatrium of theheart).

slide92

VISCERA OF NECK

  • Thecervicalvisceraaredisposed in threelayers, namedfortheirprimaryfunction. Superficialtodeep, theyarethe:
  • Endocrinelayer: thethyroidandparathyroidglands.
  • Respiratorylayer: thelarynxandtrachea.
  • Alimentarylayer: thepharynxandesophagus
slide93

Endocrine Layer of Cervical Viscera

  • The cervical organs in the endocrine layer are part of the body's endocrine system of ductless, hormone-secreting glands.
  • The thyroid gland is the body's largest endocrine gland. It produces thyroid hormone, which controls the rate of metabolism, and calcitonin, a hormone controlling calcium metabolism.
  • The thyroid gland affects all areas of the body except itself and the spleen, testes, and uterus.
slide94

The hormone produced by the parathyroid glands, parathormone (PTH), controls the metabolism of phosphorus and calcium in the blood.

  • The parathyroid glands target the skeleton, kidneys, and intestine.
slide95

THYROID GLAND

  • Thethyroidglandliesdeeptothesternothyroidandsternohyoidmuscles, locatedanteriorly in theneck.
  • Itconsistsprimarily of rightandleftlobes, anterolateraltothelarynxandtrachea.
slide96

A relativelythinisthmusunitesthelobesoverthetrachea, usuallyanteriortothesecondandthirdtrachealrings.

  • A pyramidallobe is oftenpresent, and it projectsupwardfromtheisthmus, usuallytotheleft of themidline.
slide97

Vasculature of theThyroidGland

  • Thehighlyvascularthyroidgland is suppliedbythesuperiorandinferiorthyroidarteries.
  • Thesevesselsliebetweenthefibrouscapsuleandtheloosefascialsheath.
  • Threepairs of thyroidveinsusually form a thyroidplexus of veins on theanteriorsurface of thethyroidgland.
  • Thelymphfromthethyroidglanddrainsintosuperficialanddeepcervicallymphnodes.
slide100

Nervesof ThyroidGland

  • Thenerves of thethyroidglandarederivedfromthesuperior, middle, andinferiorcervical (sympathetic) ganglia.
  • Theyreachtheglandthroughthecardiacandsuperiorandinferiorthyroidperiarterialplexusesthataccompanythethyroidarteries.
  • Thesefibersarevasomotor, not secretomotor. Theycauseconstriction of bloodvessels. Endocrinesecretionfromthethyroidgland is hormonallyregulatedbythepituitarygland.
slide103

PARATHYROID GLANDS

  • Thesmallflattened, oval parathyroidglandsusuallylieexternaltothethyroidcapsule on themedialhalf of theposteriorsurface of eachlobe of thethyroidgland, inside itssheath.
  • Mostpeoplehavefourparathyroidglands.
slide105

Vesselsof theParathyroidGlands

  • Becausetheinferiorthyroidarteriesprovidetheprimarybloodsupplytotheposterioraspect of thethyroidglandwheretheparathyroidglandsarelocated.
  • Parathyroidveinsdrainintothethyroidplexus of veinsof thethyroidglandandtrachea.
  • Lymphaticvesselsdrainintodeepcervicallymphnodesandparatracheallymphnodes.
slide106

Nerves of theParathyroidGlands

  • Thenervesupply of theparathyroidglands is abundant; it is derivedfromthyroidbranches of thecervical (sympathetic) ganglia.
  • Likethenervestothethyroid, theyarevasomotorratherthansecretomotorbecausetheseglandsarehormonallyregulated.