head and neck embryology.pdf

Head and Neck Head and Neck EmbryologyEmbryology

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Prepared by :Wiam Khader Supervised by : Dr Omar Ghannam

John

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John

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Head & Neck EmbryologyHead & Neck Embryology

BranchialBranchial ApparatusApparatusThyroid GlandThyroid GlandTongueTongueDevelopment of the faceDevelopment of the face–– NoseNose–– PalatePalate

EarEar

BranchialBranchial ApparatusApparatus

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 first Contribute mostly to neck development but the first arch contributes to facial developmentarch contributes to facial development


ArchesArches–– mesenchymalmesenchymal tissue surrounded by ectoderm tissue surrounded by ectoderm

and endodermand endoderm

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

surfacesurface

PouchesPouches–– OutpouchingOutpouching of endoderm from foregutof endoderm from foregut–– Penetrate adjacent Penetrate adjacent mesenchymemesenchyme

BranchialBranchial ArchesArches

Each arch contains:Each arch contains:

A A cartilagenouscartilagenous componentcomponent

A muscular componentA muscular component

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

A nerveA nerve

First First BranchialBranchial ArchArch

Divides early into 2 portionsDivides early into 2 portions–– MaxillaryMaxillary 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 the Dorsal end becomes the malleusmalleus and and incusincus–– Intermediate portion regresses, but the Intermediate portion regresses, but the perichondriumperichondrium

forms:forms:Anterior ligament of the Anterior ligament of the malleusmalleusSphenomandibularSphenomandibular ligamentligament

–– Ventral portion forms the mandibleVentral portion forms the mandible

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**Patiente with hypoplasia of the mandible are suspected to have anomalies in the mallelous and incus


Muscular componentMuscular component

Muscles of mastication (Muscles of mastication (temporalistemporalis, , massetermasseter, med & lat , med & lat pterygoidspterygoids))AccessorymusclesAccessorymuscles of mastication (of mastication (mylohyoidmylohyoid, ant belly of , ant belly of digastricdigastric))Tensor tympaniTensor tympaniTensor Tensor veliveli palatinipalatini


Aortic archAortic archMaxillary arteryMaxillary artery

NerveNerveTrigeminal nerve (CN V)Trigeminal nerve (CN V)

Second Second BranchialBranchial ArchArch

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

processprocess–– Intermediate portion regresses and Intermediate portion regresses and perichondriumperichondrium forms forms

the the stylohyoidstylohyoid ligamentligament–– Ventral end forms the lesser Ventral end forms the lesser cornucornu of the hyoid and the of 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 facial Migrates over superficial face to form the muscles of facial

expressionexpression–– StapediusStapedius musclemuscle–– StylohyoidStylohyoid musclemuscle–– Posterior belly of Posterior belly of digastricdigastric

Aortic ArchAortic Arch–– Hyoid arteryHyoid artery–– StapedialStapedial arteryartery


NerveNerveFacial Nerve (CN VII)Facial Nerve (CN VII)

Third Third BranchialBranchial ArchArch

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 greater the hyoid and the greater cornucornu

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

Aortic ArchAortic Arch–– Common carotid, external carotid, proximal internal Common carotid, external carotid, proximal internal

carotidcarotid

Third Third BranchialBranchial ArchArch

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

Fourth Fourth BranchialBranchial ArchArch

CartilageCartilage–– Thyroid cartilageThyroid cartilage

Muscular ComponentMuscular Component–– The 3 pharyngeal constrictorsThe 3 pharyngeal constrictors–– CricothyroidCricothyroid musclemuscle

Aortic ArchAortic Arch–– Left: Aortic archLeft: Aortic arch–– Right: Right Right: Right subclaviansubclavian

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

Sixth Sixth BranchialBranchial ArchArch

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

Muscular ComponentMuscular Component–– Intrinsic muscles of larynxIntrinsic muscles of larynx

Aortic ArchAortic 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 Arches SummarySummary

BranchialBranchial Clefts Clefts (or grooves)(or grooves)

4 clefts4 clefts

The 2The 2ndnd to 4to 4thth clefts become buried by the clefts become buried by the overgrowth of the 2overgrowth of the 2ndnd arch to form the cervical arch to form the cervical sinussinus

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

The first cleft persists and invades the The first cleft persists and invades the mesenchymemesenchymeopposite 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

11stst Pharyngeal PouchPharyngeal Pouch

Elongates into the Elongates into the tubotympanictubotympanic recessrecess

The distal part contacts the 1The distal part contacts the 1stst pharyngeal cleft and pharyngeal cleft and forms the inner lining of the TMforms the inner lining of the TM

The The tubotympanictubotympanic recess becomes the tympanic recess becomes the tympanic cavity and mastoid cavity and mastoid antrumantrum

Connection of the recess with the pharynx becomes Connection of the recess with the pharynx becomes the the eustachianeustachian tubetube

22ndnd Pharyngeal PouchPharyngeal Pouch

Forms the Forms the tonsillartonsillar fossafossa

Endoderm forms the surface epithelium and lining Endoderm 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

33rdrd Pharyngeal PouchPharyngeal Pouch

Forms 2 Forms 2 diverticuladiverticula: dorsal and ventral: dorsal and ventral

Endoderm of Endoderm of dorsaldorsal diverticuladiverticula: : infinf parathyroidparathyroid

Endoderm of Endoderm of ventraventral l diverticuladiverticula: lobule of thymus: lobule of thymus

These These diverticuladiverticula become detached from the wall become detached from the wall and migrate caudally.and migrate caudally.

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

44thth Pharyngeal PouchPharyngeal Pouch

Also develops dorsal and ventral Also develops dorsal and ventral diverticuladiverticula

The The dorsaldorsal bud becomes the sup. parathyroidbud becomes the sup. parathyroid

The The ventralventral bud becomes the bud becomes the UltimobranchialUltimobranchialbodybody

The The ultimobranchialultimobranchial body fuses with the thyroid body fuses with the thyroid gland and disseminates within it to give the gland and disseminates within it to give the parafollicularparafollicular C cells which produce C cells which produce calcitonincalcitonin


55thth pouch never developspouch never developsControversy re: Controversy re: originoforiginof ultimobranchialultimobranchialbodybody

ThyroidThyroid

In 4In 4thth week begins as week begins as endodermalendodermal thickening in floor of thickening in floor of primitive pharynxprimitive pharynxThe thickening becomes an The thickening becomes an outpouchingoutpouching: thyroid : thyroid diverticulumdiverticulumThyroid descends anterior to hyoid and thyroid cartilageThyroid descends anterior to hyoid and thyroid cartilageConnected to tongue by Connected to tongue by thyroglossalthyroglossal ductductWeek 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, just pharynx, just rostralrostral to foramen to foramen cecumcecum: : Median Tongue BudMedian Tongue Bud((TuberculumTuberculum imparimpar))

Distal Tongue BudsDistal Tongue Buds develop develop just lateral to median tongue budjust lateral to median tongue bud

Both of the above originate in Both of the above originate in mesenchymemesenchyme of first of first branchialbranchialarcharch

TongueTongue

Distal tongue buds overgrow the Distal tongue buds overgrow the median tongue bud and merge with median 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 adult Median tongue bud forms no adult structurestructure

TongueTongue

At same time 2 elevations develop caudal At same time 2 elevations develop caudal to foramen to foramen cecumcecum::

1. Copula: from 21. Copula: from 2ndnd archarch2. 2. HypobranchialHypobranchial emminenceemminence: :

from 3from 3rdrd & 4& 4thth archesarchesThe The hypobranchialhypobranchial emminenceemminenceovergrows the copula which disappearsovergrows the copula which disappearsThe post 1/3 of the tongue is formed by The post 1/3 of the tongue is formed by the the rostralrostral part of the part of the hypobranchialhypobranchialemminenceemminence (Arch 3)(Arch 3)Caudal part of Caudal part of hypobranchialhypobranchial emminenceemminence(Arch 4) forms the epiglottis(Arch 4) forms the epiglottis

TongueTongue

BranchialBranchial mesenchymemesenchymeforms the soft tissue, forms the soft tissue, vascular and vascular and lymphaticslymphaticsof the tongue.of the tongue.Tongue muscles Tongue muscles originate from the originate from the occipital occipital somitessomites which which bring with them bring with them innervationinnervation (CN XII)(CN XII)

TongueTongue

InnervationInnervation to tongue:to tongue:Ant 2/3: CN VAnt 2/3: CN VPost 1/3: CN IXPost 1/3: CN IX

Development of the FaceDevelopment of the Face

Five facial Five facial primordiaprimordia contribute to development of the face:contribute to development of the face:–– The The frontonasalfrontonasal prominenceprominence–– Paired Maxillary prominencesPaired Maxillary prominences–– Paired Paired MandibularMandibular prominencesprominences


44thth week: thickening of ectoderm in the week: thickening of ectoderm in the ventrolateralventrolateral parts of parts of the FNP: the FNP: Nasal Nasal PlacodesPlacodes

MesenchymeMesenchyme on the edges of the on the edges of the placodesplacodes proliferates to proliferates 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 called now 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 the These nasal cavities are separated from the oral cavity by the oronasaloronasal membranesmembranes which rupture to form the primitive which rupture to form the primitive choanachoana


Growth of maxillary Growth of maxillary prominences pushes medial prominences pushes medial nasal prominences mediallynasal prominences medially

These fuse to form the These fuse to form the nasal bulb, the nasal bulb, the philtrumphiltrum, , the the premaxillarypremaxillary segment of segment of the maxilla and the the maxilla and the primitive palateprimitive palate


The lateral nasal prominences, which become the ala are The lateral nasal prominences, which become the ala are separated from the maxillary prominences by the separated from the maxillary prominences by the nnasolacrimalasolacrimal grooves grooves which become the which become the nasolacrimalnasolacrimalducts.ducts.

The sinuses form as The sinuses form as outpouchingsoutpouchings of the ectoderm of lateral of the ectoderm of lateral nasal wallsnasal walls

The olfactory epithelium develops from ectodermThe olfactory epithelium develops from ectoderm

PalatePalate

Primary and Secondary PalatePrimary and Secondary Palate

Primary PalatePrimary PalateDevelops from the fusion of the medial nasal prominences Develops from the fusion of the medial nasal prominences between the maxillary prominencesbetween the maxillary prominencesForms the adult portion of the palate which is anterior to the Forms the adult portion of the palate which is anterior to the incisive foramenincisive foramen

PalatePalate

Secondary PalateSecondary PalateOrigin of the hard and soft palateOrigin of the hard and soft palateDevelops from internal projections of the maxillary Develops from internal projections of the maxillary prominences called the prominences called the lateral palatine processeslateral palatine processesAs mandible develops, the tongue drops and the palatine As mandible develops, the tongue drops and the palatine processes 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 an Ossification occurs in an anteroantero--posterior directionposterior direction

The EarThe Ear

Inner EarInner Ear44thth week: thickening in surface ectoderm called week: thickening in surface ectoderm called oticotic placodeplacodeInvaginatesInvaginates into underlying into underlying mesenchymemesenchyme and detaches from and detaches from ectoderm: now called ectoderm: now called oticotic vesiclevesicleOticOtic vesicle divides into 2 regions: vesicle divides into 2 regions: utricularutricular portion and portion and saccularsaccular portionportion

UtricularUtricular portionportionUtricle, semicircular canals and Utricle, semicircular canals and endolymphaticendolymphatic ductduct

SaccularSaccular portionportionSacculeSaccule and cochlear duct (becomes cochlea)and cochlear duct (becomes cochlea)

Inner EarInner Ear

Middle EarMiddle Ear

External EarExternal Ear

Develops from 6 Develops from 6 mesenchymalmesenchymal swellings, called swellings, called auricular auricular hillockshillocks, which develop around the first , which develop around the first branchialbranchial cleftcleftThe The mesenchymemesenchyme is derived from mesoderm in the first and is derived from mesoderm in the first and 22ndnd branchialbranchial arches. As the ear grows, arches. As the ear grows, contrbutionscontrbutions of the of the first first branchialbranchial arch become reduced.arch become reduced.The The pinnapinna initially develops in the neck. As the mandible initially develops in the neck. As the mandible grows, 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 first Part of the auricle originating from the first branchialbranchial arch is arch is innervated by CN Vinnervated by CN VThe part originating from the 2The part originating from the 2ndnd arch is innervated by the arch is innervated by the cervical plexus (namely the lesser occipital and greater cervical plexus (namely the lesser occipital and greater auricular nerves)auricular nerves)

External EarExternal Ear

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