head and neck embryology

8/8/2019 Head and Neck Embryology

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Head and Neck Head and Neck EmbryologyEmbryology



Head & Neck EmbryologyHead & Neck Embryology

BranchialBranchial Apparatus Apparatus Thyroid GlandThyroid Gland

TongueTongue Development of the faceDevelopment of the face

– – NoseNose

– – PalatePalate

EarEar



BranchialBranchial Apparatus Apparatus

4 arches are well developed by 44 arches are well developed by 4thth week of gestationweek of gestation

55thth and 6and 6thth arches are still rudimentaryarches are still rudimentary

Development takes place over weeks 4 to 7Development takes place over weeks 4 to 7

Contribute mostly to neck development but the firstContribute mostly to neck development but the first

arch contributes to facial developmentarch contributes to facial development




Arches Arches – – mesenchymalmesenchymal tissue surrounded by ectodermtissue surrounded by ectoderm

and endodermand endoderm

Clefts (or grooves)Clefts (or grooves) – – Separate adjacent arches alongSeparate adjacent arches along ectodermalectodermal

surfacesurface

PouchesPouches – – OutpouchingOutpouching of endoderm from foregutof endoderm from foregut

– – Penetrate adjacentPenetrate adjacent mesenchymemesenchyme



BranchialBranchial Arches Arches

Each arch contains:Each arch contains:

A A cartilagenouscartilagenous componentcomponent

A muscular component A muscular component

An aortic arch (artery) An aortic arch (artery)

A nerve A nerve



FirstFirst BranchialBranchial Arch Arch

Divides early into 2 portionsDivides early into 2 portions – – MaxillaryMaxil lary process dorsally (maxilla,process dorsally (maxilla, zygomazygoma,, squamoussquamous

temporal bone)temporal bone)

– – MandibularMandibular process ventrallyprocess ventrally




Cartilage (Cartilage (MeckelMeckel’ ’ ss Cartilage)Cartilage) – – Dorsal end becomes theDorsal end becomes the malleusmalleus andand incusincus

– – Intermediate portion regresses, but theIntermediate portion regresses, but the perichondriumperichondrium

forms:forms:

Anterior ligament of the Anterior ligament of the malleusmalleus SphenomandibularSphenomandibular ligamentligament

– – Ventral portion forms the mandible Ventral portion forms the mandible




Muscular componentMuscular component

Muscles of mastication (Muscles of mastication (temporalistemporalis,, massetermasseter, med & lat, med & lat

pterygoidspterygoids))

Accessorymuscles Accessorymuscles of mastication (of mastication (mylohyoidmylohyoid, ant belly of , ant belly of digastricdigastric))

Tensor tympaniTensor tympani

TensorTensor veliveli palatinipalatini




Aortic arch Aortic arch Maxillary arteryMaxillary artery

NerveNerve Trigeminal nerve (CN V)Trigeminal nerve (CN V)



SecondSecond BranchialBranchial Arch Arch

Cartilage (ReichertCartilage (Reichert’ ’ s Cartilage)s Cartilage) – – Dorsal end becomes stapes (except footplate) andDorsal end becomes stapes (except footplate) and styloidstyloid

processprocess

– – Intermediate portion regresses andIntermediate portion regresses and perichondriumperichondrium formsforms

thethe stylohyoidstylohyoid ligamentligament – – Ventral end forms the lesser Ventral end forms the lesser cornucornu of the hyoid and theof the hyoid and the

upper half of the hyoid boneupper half of the hyoid bone




Muscular ComponentMuscular Component – – Migrates over superficial face to form the muscles of facialMigrates over superficial face to form the muscles of facial

expressionexpression

– – StapediusStapedius musclemuscle

– – StylohyoidStylohyoid musclemuscle – – Posterior belly of Posterior belly of digastricdigastric

Aortic Arch Aortic Arch – – Hyoid arteryHyoid artery

– – StapedialStapedial arteryartery




NerveNerve Facial Nerve (CN VII)Facial Nerve (CN VII)



ThirdThird BranchialBranchial Arch Arch

CartilageCartilage – – Located ventrally and forms the lower half of the body of Located ventrally and forms the lower half of the body of the hyoid and the greaterthe hyoid and the greater cornucornu

Muscular ComponentMuscular Component – – Only one muscle:Only one muscle: stylopharyngeusstylopharyngeus

Aortic Arch Aortic Arch – – Common carotid, external carotid, proximal internalCommon carotid, external carotid, proximal internalcarotidcarotid



ThirdThird BranchialBranchial Arch Arch

NerveNerve – – GlossopharyngealGlossopharyngeal (CN IX)(CN IX)



FourthFourth BranchialBranchial Arch Arch

CartilageCartilage – – Thyroid cartilageThyroid cartilage

Muscular ComponentMuscular Component

– – The 3 pharyngeal constrictorsThe 3 pharyngeal constrictors – – CricothyroidCricothyroid musclemuscle

Aortic Arch Aortic Arch – – Left: Aortic archLeft: Aortic arch

– – Right: RightRight: Right subclaviansubclavian

NerveNerve – – Superior laryngeal branch of Superior laryngeal branch of vagusvagus (CN X)(CN X)



SixthSixth BranchialBranchial Arch Arch

CartilageCartilage – – CricoidCricoid cartilage,cartilage, arytenoidarytenoid,, corniculatecorniculate and cuneiformand cuneiform

Muscular ComponentMuscular Component

– – Intrinsic muscles of larynxIntrinsic muscles of larynx

Aortic Arch Aortic Arch – – Left: pulmonary artery,Left: pulmonary artery, ductusductus arteriosusarteriosus

– – Right: pulmonary artery, distal end degeneratesRight: pulmonary artery, distal end degenerates

NerveNerve – – Recurrent laryngeal nerve of Recurrent laryngeal nerve of vagusvagus (CN X)(CN X)



BranchialBranchial Arches ArchesSummarySummary



BranchialBranchial CleftsClefts(or grooves)(or grooves)

4 clefts4 clefts

The 2The 2ndnd to 4to 4thth clefts become buried by theclefts become buried by the

overgrowth of the 2overgrowth of the 2ndnd arch to form the cervicalarch to form the cervical

sinussinus

Cervical sinus hasCervical sinus has dissapeareddissapeared by week 7by week 7

The first cleft persists and invades theThe first cleft persists and invades the mesenchymemesenchyme

opposite the first pouchopposite the first pouch

This becomes the EAC and ectoderm of the TMThis becomes the EAC and ectoderm of the TM



BranchialBranchial CleftsClefts



Pharyngeal PouchesPharyngeal Pouches



11 stst Pharyngeal PouchPharyngeal Pouch

Elongates into theElongates into the tubotympanictubotympanic recessrecess

The distal part contacts the 1The distal part contacts the 1stst pharyngeal cleft andpharyngeal cleft and

forms the inner lining of the TMforms the inner lining of the TM

TheThe tubotympanictubotympanic recess becomes the tympanicrecess becomes the tympanic

cavity and mastoidcavity and mastoid antrumantrum

Connection of the recess with the pharynx becomesConnection of the recess with the pharynx becomesthethe eustachianeustachian tubetube



22 ndnd Pharyngeal PouchPharyngeal Pouch

Forms theForms the tonsillartonsillar fossafossa

Endoderm forms the surface epithelium and liningEndoderm forms the surface epithelium and lining

of of tonsillartonsillar cryptscrypts

At 20 weeks lymphoid tissue invades the endoderm At 20 weeks lymphoid tissue invades the endoderm

and forms the palatine tonsilsand forms the palatine tonsils



33 rdrd Pharyngeal PouchPharyngeal Pouch

Forms 2Forms 2 diverticuladiverticula: dorsal and ventral: dorsal and ventral Endoderm of Endoderm of dorsaldorsal diverticuladiverticula:: inf inf parathyroidparathyroid

Endoderm of Endoderm of ventraventra ll diverticuladiverticula: lobule of thymus: lobule of thymus

TheseThese diverticuladiverticula become detached from the wallbecome detached from the wall

and migrate caudally.and migrate caudally.

Thymus comes to lie in the superiorThymus comes to lie in the superior mediastinummediastinum



44 thth Pharyngeal PouchPharyngeal Pouch

Also develops dorsal and ventral Also develops dorsal and ventral diverticuladiverticula TheThe dorsaldorsal bud becomes the sup. parathyroidbud becomes the sup. parathyroid

TheThe ventralventral bud becomes thebud becomes the UltimobranchialUltimobranchial

bodybody

TheThe ultimobranchialultimobranchial body fuses with the thyroidbody fuses with the thyroid

gland and disseminates within it to give thegland and disseminates within it to give the

parafollicularparafollicular C cells which produceC cells which produce calcitonincalcitonin




55thth

pouch never developspouch never develops Controversy re:Controversy re: originof originof ultimobranchialultimobranchial

bodybody



ThyroidThyroid

In 4In 4thth week begins asweek begins as endodermalendodermal thickening in floor of thickening in floor of

primitive pharynxprimitive pharynx

The thickening becomes anThe thickening becomes an outpouchingoutpouching: thyroid: thyroid diverticulumdiverticulum

Thyroid descends anterior to hyoid and thyroid cartilageThyroid descends anterior to hyoid and thyroid cartilage

Connected to tongue byConnected to tongue by thyroglossalthyroglossal ductduct

Week 7: Thyroid reaches final positionWeek 7: Thyroid reaches final position

ThyroglossalThyroglossal duct has degeneratedduct has degenerated

Pyramidal lobe: Persistence of distal end of Pyramidal lobe: Persistence of distal end of thyroglossalthyroglossal ductductPresent in 50% of peoplePresent in 50% of people



ThyroidThyroid



TongueTongue

44thth week: elevation on floor of week: elevation on floor of

pharynx, justpharynx, just rostralrostral to foramento foramen

cecumcecum:: Median Tongue BudMedian Tongue Bud

((TuberculumTuberculum imparimpar))

Distal Tongue BudsDistal Tongue Buds developdevelop just lateral to median tongue bud just lateral to median tongue bud

Both of the above originate inBoth of the above originate in

mesenchymemesenchyme of firstof first branchialbranchialarcharch



TongueTongue

Distal tongue buds overgrow theDistal tongue buds overgrow the

median tongue bud and merge withmedian tongue bud and merge with

each othereach other

These form the ant 2/3 of the tongueThese form the ant 2/3 of the tongue

Median tongue bud forms no adultMedian tongue bud forms no adult

structurestructure



TongueTongue

At same time 2 elevations develop caudal At same time 2 elevations develop caudal

to foramento foramen cecumcecum::

1. Copula: from 21. Copula: from 2ndnd archarch

2.2. HypobranchialHypobranchial emminenceemminence::

from 3from 3rdrd & 4& 4thth archesarches

TheThe hypobranchialhypobranchial emminenceemminenceovergrows the copula which disappearsovergrows the copula which disappears

The post 1/3 of the tongue is formed byThe post 1/3 of the tongue is formed by

thethe rostralrostral part of thepart of the hypobranchialhypobranchial

emminenceemminence (Arch 3)(Arch 3)

Caudal part of Caudal part of hypobranchialhypobranchial emminenceemminence(Arch 4) forms the epiglottis(Arch 4) forms the epiglottis



TongueTongue

BranchialBranchial mesenchymemesenchyme

forms the soft tissue,forms the soft tissue,vascular andvascular and lymphaticslymphatics

of the tongue.of the tongue.

Tongue musclesTongue muscles

originate from theoriginate from theoccipitaloccipital somitessomites whichwhich

bring with thembring with them

innervationinnervation (CN XII)(CN XII)



TongueTongue

InnervationInnervation

to tongue:to tongue:

Ant 2/3: CN V Ant 2/3: CN V

Post 1/3: CN IXPost 1/3: CN IX



Development of the FaceDevelopment of the Face

Five facialFive facial primordiaprimordia contribute to development of the face:contribute to development of the face:

– – TheThe frontonasalfrontonasal prominenceprominence

– – Paired Maxillary prominencesPaired Maxillary prominences

– – PairedPaired MandibularMandibular prominencesprominences




44thth week: thickening of ectoderm in theweek: thickening of ectoderm in the ventrolateralventrolateral parts of parts of

the FNP:the FNP: NasalNasal PlacodesPlacodes

MesenchymeMesenchyme on the edges of theon the edges of the placodesplacodes proliferates toproliferates to

form:form: medial and lateral nasal prominencesmedial and lateral nasal prominences

As a result the nasal As a result the nasal placodesplacodes now lie in a depression callednow lie in a depression called

nasal pitsnasal pits which enlarge dorsally to form the nasal cavities.which enlarge dorsally to form the nasal cavities.

These nasal cavities are separated from the oral cavity by theThese nasal cavities are separated from the oral cavity by the

oronasaloronasal membranesmembranes which rupture to form the primitivewhich rupture to form the primitive

choanachoana




Growth of maxillaryGrowth of maxillaryprominences pushes medialprominences pushes medial

nasal prominences mediallynasal prominences medially

These fuse to form theThese fuse to form thenasal bulb, thenasal bulb, the philtrumphiltrum,,

thethe premaxillarypremaxillary segment of segment of

the maxilla and thethe maxilla and the

primitive palateprimitive palate




The lateral nasal prominences, which become the ala areThe lateral nasal prominences, which become the ala are

separated from the maxillary prominences by theseparated from the maxillary prominences by thennasolacrimalasolacrimal groovesgrooves which become thewhich become the nasolacrimalnasolacrimal

ducts.ducts.

The sinuses form asThe sinuses form as outpouchingsoutpouchings of the ectoderm of lateralof the ectoderm of lateralnasal wallsnasal walls

The olfactory epithelium develops from ectodermThe olfactory epithelium develops from ectoderm



PalatePalate

Primary and Secondary PalatePrimary and Secondary Palate

Primary PalatePrimary Palate Develops from the fusion of the medial nasal prominencesDevelops from the fusion of the medial nasal prominences

between the maxillary prominencesbetween the maxillary prominences

Forms the adult portion of the palate which is anterior to theForms the adult portion of the palate which is anterior to the

incisive foramenincisive foramen



PalatePalate

Secondary PalateSecondary Palate Origin of the hard and soft palateOrigin of the hard and soft palate

Develops from internal projections of the maxillaryDevelops from internal projections of the maxillary

prominences called theprominences called the lateral palatine processeslateral palatine processes

As mandible develops, the tongue drops and the palatine As mandible develops, the tongue drops and the palatineprocesses grow medially and fuse in the midline.processes grow medially and fuse in the midline.

They also fuse with the nasal septum and the primary palate.They also fuse with the nasal septum and the primary palate.

Ossification occurs in anOssification occurs in an anteroantero--posterior directionposterior direction



The EarThe Ear

Inner EarInner Ear 44thth week: thickening in surface ectoderm calledweek: thickening in surface ectoderm called oticotic placodeplacode

InvaginatesInvaginates into underlyinginto underlying mesenchymemesenchyme and detaches fromand detaches from

ectoderm: now calledectoderm: now called oticotic vesiclevesicle

OticOtic vesicle divides into 2 regions:vesicle divides into 2 regions: utricularutricular portion andportion andsaccularsaccular portionportion

UtricularUtricular portionportion

Utricle, semicircular canals andUtricle, semicircular canals and endolymphaticendolymphatic ductduct

SaccularSaccular portionportion

SacculeSaccule and cochlear duct (becomes cochlea)and cochlear duct (becomes cochlea)



Inner EarInner Ear



Middle EarM iddle Ear



External EarExternal Ear

Develops from 6Develops from 6 mesenchymalmesenchymal swellings, calledswellings, called auricularauricular

hillockshillocks , which develop around the first, which develop around the first branchialbranchial cleftcleft

TheThe mesenchymemesenchyme is derived from mesoderm in the first andis derived from mesoderm in the first and

22ndnd branchialbranchial arches. As the ear grows,arches. As the ear grows, contrbutionscontrbutions of theof the

firstfirst branchialbranchial arch become reduced.arch become reduced.

TheThe pinnapinna initially develops in the neck. As the mandibleinitially develops in the neck. As the mandiblegrows, it moves up to the level of the eyes.grows, it moves up to the level of the eyes.

Part of the auricle originating from the firstPart of the auricle originating from the first branchialbranchial arch isarch is

innervated by CN Vinnervated by CN V

The part originating from the 2The part originating from the 2ndnd arch is innervated by thearch is innervated by thecervical plexus (namely the lesser occipital and greatercervical plexus (namely the lesser occipital and greater

auricular nerves)auricular nerves)



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head and neck embryology

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