Development of Face-Theory

8/3/2019 Development of Face-Theory

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IINTRODUCTIONNTRODUCTION

• Embryology:-Embryology:- Study of development of anStudy of development of anindividual before birth.individual before birth.

• Why a medical student should studyWhy a medical student should studyembryology???embryology???– This subject tells how the organs of the body

develop.

– It helps us to understand many complicatedfacts of adult anatomy.– To understand abnormal growth &

development it is very much essential to know

the normal pattern of growth & development.





























DEFINITIONSDEFINITIONS

• Growth:Growth:

Self multiplication of living substancesSelf multiplication of living substances(J.S.HUXLEY)(J.S.HUXLEY)

- An increase in size- An increase in size((TODD)TODD)- Increase in size, change in proportion & progressive- Increase in size, change in proportion & progressive

complexitycomplexity (KROGMAN)(KROGMAN)- Change in any morphologic parameter which isChange in any morphologic parameter which is

measurablemeasurable (MOSS)(MOSS)Development:Development:

Progress towards maturityProgress towards maturity (TODD)(TODD)





































TERMINOLOGY & ABBREVATIONSTERMINOLOGY & ABBREVATIONS

• STOMATODEUM:STOMATODEUM: It is the future mouth.It is the future mouth.It is a depression bounded cranially by aIt is a depression bounded cranially by a

bulging produced by the brain & cauduallybulging produced by the brain & cauduallyby a bulging produced by the pericardialby a bulging produced by the pericardialcavity.cavity.

• NP- Nasal Process.NP- Nasal Process.

• MNP-Medial Nasal Process.MNP-Medial Nasal Process.• LNP – Lateral Nasal Process.LNP – Lateral Nasal Process.• MP – Maxillary Prominences.MP – Maxillary Prominences.• E.O – Enamel OrganE.O – Enamel Organ

































DEVELOPMENT OF FACE

Begins at 4th week with the facial prominences consistingprimarily of neural crest derived mesenchyme & formedmainly by the 1st pair of pharygeal arches.

The maxillary prominences can be seen lateral to thestomatodeum & Mandibular prominences caudal to it.

Fronto nasal prominence formed by proliferation ofmesenchyme ventral to brain vesicles, constitute the upper

border of stomatodeum.

On both sides of the FNP, local thickneings of surfaceectoderm, the nasal (or) olfactory placodes are seen underinductive influence of fore brain.

























• During 5During 5thth week:week:

-- Nasal placodes invaginate to form nasal pitsNasal placodes invaginate to form nasal pits

thereby creating a ridge of tissue aroundthereby creating a ridge of tissue aroundeach pit, the nasal prominence(NP).each pit, the nasal prominence(NP).

- Outer edge of NP is lateral nasal- Outer edge of NP is lateral nasal

Prominence & inner edge is Medial nasalProminence & inner edge is Medial nasalprominence.prominence.
























• During 6th & 7th Weeks:- Maxillary prominences increase in size growingmedially, compressing the MNP towards themidline. As a result, they fuse. Hence, the upperlip is formed by two MNP & two MP.- LNP does not participate in the formation ofupper lip.

- Mandibular prominence forms the jaws & lower lipthat merge across the midline.

- MP & LNP are separated by a deep furrow, thenasolacrimal groove.

- Ectoderm in the floor of this groove forms a solidepithelial cord which forms nasolacrimal duct; itsupper end widens to form the lacrimal sac.

























- The MP enlarge to form cheek and maxillae.- Nose is formed from 5 facial prominences

which are:

- Bridge from frontal prominence.

- crest & tip from merged MNP.

- Alae from LNP.











DEVELOPMENT OF NOSEDEVELOPMENT OF NOSE

- During 6During 6thth weekweek the nasal pits deepenthe nasal pits deepen

considerably, partly because of growth ofconsiderably, partly because of growth ofsurrounding NP & partly because of theirsurrounding NP & partly because of theirpenetration into the underlying mesenchyme.penetration into the underlying mesenchyme.

- Nose receives contributions from:Nose receives contributions from:

.. Nasal septum – FNPNasal septum – FNP

.. Medial nasal processMedial nasal process

.. Alae – LNPAlae – LNP

--





































DEVELOPMENT OF PARANASAL SINUSESDEVELOPMENT OF PARANASAL SINUSES

Para nasal Sinuses develop asPara nasal Sinuses develop asdiverticula of the lateral nasal walls &diverticula of the lateral nasal walls &extend into corresponding bones.extend into corresponding bones.











CHEEKS:CHEEKS:

After formation of upper & lower lips,the maxillary & mandibular processundergo progressive fusion with each

other to form cheeks.









EYES:EYES:

.. Region of eye is first seen as an

ectodermal thickening – the lensplacode, which appears on ventrallateral side of developing forebrain,

lateral & cranial to nasal placode.












. The placode sinks below the surface & is

eventually cut off from surfaceectoderm.

. The developing eyeballs produces abulging which are first directed laterally

& lie in the angles b/w MP & LNP.. With the narrowing of FNP they come to

face forwards.

. The eyelids are derived from folds ofectoderm that are formed above & belowthe eyes & by mesoderm enclosed with inthe folds.
















MOLECULAR REGULATION OFMOLECULAR REGULATION OFFACIAL DEVELOPMENT FACIAL DEVELOPMENT

• Much of face is derived from neuralMuch of face is derived from neuralcrest cells that migrate into pharyngealcrest cells that migrate into pharyngeal

arches from the edges of cranial neuralarches from the edges of cranial neuralfold.fold.• In the hind brain, these cells originateIn the hind brain, these cells originate

from segmented regions known asfrom segmented regions known as

RHOMBOMERES.RHOMBOMERES.• There are eight of these segmentsThere are eight of these segments

(R1-R8).(R1-R8).




























• Crest cells from specific segmentsCrest cells from specific segmentspopulate specific arches.populate specific arches.

- Midbrain + R1,R2- Midbrain + R1,R2 -- 11stst archarchR4R4 -- 22ndnd archarch

R6,R7R6,R7 -- 33rdrd archarch

R8R8 -- 44thth & 6& 6thth archesarches





















































• Patterning of pharyngeal arches appears toPatterning of pharyngeal arches appears tobe regulated bybe regulated by HOX GENESHOX GENES which arewhich are

carried to arches by migrating neural crestcarried to arches by migrating neural crestcells.cells.

• Retinoids (Retinoic Acid)Retinoids (Retinoic Acid) can also regulatecan also regulateHOX gene expression in a concentrationHOX gene expression in a concentrationdependent manner throughdependent manner through RARE’S.RARE’S.

• In addition to the HOX genes,In addition to the HOX genes, OTX2OTX2 maymayprecipitate in morphogenesis of 1precipitate in morphogenesis of 1stst arch.arch.








































PHARYNGEAL ARCHESPHARYNGEAL ARCHES

- Each arch consists of a core ofEach arch consists of a core ofmesenchymal tissue covered on the outsidemesenchymal tissue covered on the outside

by surface ectoderm & on the inside byby surface ectoderm & on the inside byepithelium of endodermal origin.epithelium of endodermal origin.

- In addition, they also contain neural crestIn addition, they also contain neural crestcells which contribute to skeletalcells which contribute to skeletal

components of face.components of face.- Mesoderm gives rise to musculature of faceMesoderm gives rise to musculature of face& neck.& neck.

- Each arch has 3 components: Muscular,Each arch has 3 components: Muscular,

Nerve, ArterialNerve, Arterial-
































DEVELOPMENT OF TONGUEDEVELOPMENT OF TONGUE

.. Appears atAppears atapproximatelyapproximately 4 weeks4 weeks in the form of 2 lateralin the form of 2 lateral

lingual swellings & 1lingual swellings & 1medial swelling, themedial swelling, thetuberculum impar.tuberculum impar.These 3 originate fromThese 3 originate from

11stst

arch.arch.. A second median. A second median

swelling, copula (or)swelling, copula (or)hypobranchial eminencehypobranchial eminence

is formed by mesodermis formed by mesodermof 2 3 & 4 arches.of 2,3 & 4 arches.








































As lateral swellingsAs lateral swellingsincreases in size, theyincreases in size, theyovergrow tuberculumovergrow tuberculumimpar forming anteriorimpar forming anterior2/3 of tongue.2/3 of tongue.

. Posterior 1/3 develops. Posterior 1/3 developsfrom 2,3,& part of 4from 2,3,& part of 4thth arches with 3arches with 3rdrd archarchburying the 2burying the 2ndnd arch.arch.

. Muscles of tongue. Muscles of tonguedevelop fromdevelop from occipitaloccipitalsomites/myotomessomites/myotomes..










































OVER ALL DEVELOPMENT OF TONGUE




• CLINICAL CORRELATION &CLINICAL CORRELATION &ANOMALIES:ANOMALIES:

-- AnkyloglossiaAnkyloglossia

-- MacroglossiaMacroglossia

-- MicroglossiaMicroglossia

-- Fissured tongueFissured tongue

-- AglossiaAglossia

-- Bifid tongueBifid tongue
































DEVELOPMENT OF PALATEDEVELOPMENT OF PALATE

• INTERMAXILLARY SEGMENT:INTERMAXILLARY SEGMENT:

-- formed due to merging of two medialformed due to merging of two medial

nasal prominencesnasal prominences-- Composed ofComposed of

a. Labial component – forms philtrum ofa. Labial component – forms philtrum ofupper lip.upper lip.

b. Upper Jaw component – carries the 4b. Upper Jaw component – carries the 4incisorincisor

c. Palatal component – forms triangularc. Palatal component – forms triangularprimary palate.primary palate.

It is continous with nasal septum.It is continous with nasal septum.
































• SECONDARY PALATE:SECONDARY PALATE:

.. Formed by 2 shelf like outgrowths fromFormed by 2 shelf like outgrowths fromthe MP, the palatine shelves which appear inthe MP, the palatine shelves which appear inthethe 66thth weekweek of development. Directedof development. Directedobliquely on each side of tongue.obliquely on each side of tongue... In theIn the 77thth weekweek, the palatine shelves, the palatine shelvesascend horizontally above the tongue, fuseascend horizontally above the tongue, fuse& form secondary palate.& form secondary palate.

.. Anteriorly it fuses with primary palateAnteriorly it fuses with primary palatewhere incisive foramen is present.where incisive foramen is present.














































• CLINICAL CORRELATION &CLINICAL CORRELATION &






• CLINICAL CORRELATION &CLINICAL CORRELATION &ANOMALIES:ANOMALIES:

-- Facial Clefts:Facial Clefts:

Cleft LipCleft LipCleft PalateCleft Palate

-- Oblique facial clefts – failure of MP toOblique facial clefts – failure of MP to

merge with LNP.merge with LNP.-- Median cleft Lip – Rare incompleteMedian cleft Lip – Rare incompletemerging of the two MNP in the midline.merging of the two MNP in the midline.

--

Teratogens are likely to cause cleft lipTeratogens are likely to cause cleft lip

defects if the embryo is exposed to themdefects if the embryo is exposed to themduringduring 55thth & 6& 6thth weeks.weeks.

-- The palate is most susceptible b/wThe palate is most susceptible b/w 77thth &&

88thth weeks.weeks.






























































• DEVELOPMENTAL ANOMALIES OFDEVELOPMENTAL ANOMALIES OF






DEVELOPMENTAL ANOMALIES OFDEVELOPMENTAL ANOMALIES OFFACE:FACE:

-- MacrostomiaMacrostomia

-- MicrostomiaMicrostomia- Bifid Nose- Bifid Nose

-- ProboscisProboscis

-- CyclopsCyclops

-- Macro & Micro gnathiaMacro & Micro gnathia

-- HyperptelorismHyperptelorism

-- Lips with congenital pits or double lipLips with congenital pits or double lip

-- Entire 1Entire 1stst arch may be underdevelopedarch may be underdevelopedon one oron one or

both sides -both sides - MANDIBULO FACIALMANDIBULO FACIALDYSOSTOSISDYSOSTOSIS






















































TERATOLOGYTERATOLOGY

• Also known as embryopathy.Also known as embryopathy.

• Defined as the pathology of theDefined as the pathology of the

unborn.unborn.• Physical factors like radiation from X-Physical factors like radiation from X-

ray or radium produces skull defects,ray or radium produces skull defects,

cleft palate.cleft palate.




















CHEMICAL AGENTSCHEMICAL AGENTS

• AMINOPTERINAMINOPTERIN- An antimetabolite &- An antimetabolite &

antagonist of folic acid used to induceantagonist of folic acid used to induceabortion. If this fails the child showsabortion. If this fails the child showsencephaly, hydrocephalus, hare-lip or cleftencephaly, hydrocephalus, hare-lip or cleftpalate.palate.

• DIPHENYL HYDANTOINDIPHENYL HYDANTOIN – Craniofacial– Craniofacialdefectsdefects

























• DIAZEPAM (VALIUM)DIAZEPAM (VALIUM) – Cleft lip with– Cleft lip with

or without cleft palate.or without cleft palate.• TETRACYCLINESTETRACYCLINES –Tooth anomalies–Tooth anomalies• ALCOHOLALCOHOL – Short palpebral fissures &– Short palpebral fissures &

hypoplasia of maxilla.hypoplasia of maxilla.• CORTISONECORTISONE – In early pregnancy– In early pregnancy

causes cleft palate.causes cleft palate.





























SYNDROMES ASSOCIATED WITHSYNDROMES ASSOCIATED WITHDEVELOPMENTAL DEFECTS OF FACEDEVELOPMENTAL DEFECTS OF FACE

GOLDENHAR SYNDROMEGOLDENHAR SYNDROME PIERRE ROBIN SYNDROMEPIERRE ROBIN SYNDROME PARRY ROMBERG SYNDROMEPARRY ROMBERG SYNDROME VANDER WOUDE’S SYNDROMEVANDER WOUDE’S SYNDROME MELKERSON – ROSENTHAL SYNDROMEMELKERSON – ROSENTHAL SYNDROME

DOWN’S SYNDROMEDOWN’S SYNDROME BECKWITH – WIEDE MANN SYNDROMEBECKWITH – WIEDE MANN SYNDROME RUBENSTEIN- TAYBI SYNDROMERUBENSTEIN- TAYBI SYNDROME KLINEFELTER’S SYNDROMEKLINEFELTER’S SYNDROME


































DEVELOPMENT OF TOOTHDEVELOPMENT OF TOOTH

• Starts at aroundStarts at around 6 weeks6 weeks of developmentof developmentwith the continouous band of thickenedwith the continouous band of thickened

epitheliumepithelium( primary epithelial band)( primary epithelial band)

• Roughly horse shoe shaped.Roughly horse shoe shaped.

•Primary epithelial bandPrimary epithelial band

»- Vestibular lamina- Vestibular lamina

»- Dental lamina- Dental lamina






























.. The downgrowths from the dentalThe downgrowths from the dentallamina represents the beginning of thelamina represents the beginning of theenamelorgan of the tooth bud of aenamelorgan of the tooth bud of adeciduous tooth.deciduous tooth.

. As cell proliforation continues the. As cell proliforation continues theenamel organ increase in size & changesenamel organ increase in size & changesin shape.in shape.

. The stages of tooth development. The stages of tooth developmentcorrelates with the shape of the enamelcorrelates with the shape of the enamelorgan.organ.

























BUDSTAGEBUDSTAGE

• The enamel organ consists of peripherallyThe enamel organ consists of peripherallylocated low columnar cells & centrally locatedlocated low columnar cells & centrally locatedpolygonal cells.polygonal cells.

• Cells of the tooth bud& surroundingCells of the tooth bud& surroundingmesenchyme undergo mitosis.mesenchyme undergo mitosis.

• The Neural crest cells migrate to the area &The Neural crest cells migrate to the area &

the ectomesenchyme surrounding thethe ectomesenchyme surrounding thedeveloping tooth bud condense.developing tooth bud condense.• Ectomesenchyme subjacent to enamel organ isEctomesenchyme subjacent to enamel organ is

dental papilla.dental papilla.

• Ectomesenchyme surrounding E.O & dentalEctomesenchyme surrounding E.O & dental
































CAP STAGECAP STAGE

• Characterised by shallow invagination on theCharacterised by shallow invagination on thedeep surface.deep surface.

• Peripheral cuboidal cells covering thePeripheral cuboidal cells covering theconvexity –OEEconvexity –OEE• Tall, columnar cells in the concavityTall, columnar cells in the concavity

represent –IEE.represent –IEE.

• The third layer stellate reticulum is alsoThe third layer stellate reticulum is alsoseen in this stage in the centre of E.Oseen in this stage in the centre of E.O• Temporary Structures enamel knot &Temporary Structures enamel knot &

enamel chord are seen with act as reserviorenamel chord are seen with act as reservior

of dividing cells for the growing E.Oof dividing cells for the growing E.O
































E E




BELL STAGEBELL STAGE• Divided into early & advanced stages.Divided into early & advanced stages.

In addition to OEE,IEE & St.reticulumIn addition to OEE,IEE & St.reticulumanother layeranother layer STRATUM INTERMEDIUMSTRATUM INTERMEDIUM is seen present between IEE & St.Reticulumis seen present between IEE & St.Reticulum

this layer is essential for enamel formation.this layer is essential for enamel formation.• S.R collapses before enamel formationS.R collapses before enamel formation

begins, reducing the distance between thebegins, reducing the distance between thecentrally situated ameloblasts & thecentrally situated ameloblasts & the

nutrients capillaries.nutrients capillaries.• Membrana preformativa is the basementMembrana preformativa is the basement

membrane that separates E.O & Dentalmembrane that separates E.O & Dentalpapilla.papilla.



































ADVANCE BELLADVANCE BELL

• Boundary between IEE & odontoblastsBoundary between IEE & odontoblastsoutlines the future DEJ.outlines the future DEJ.

• Cervical portion of the E.O gives rise to theCervical portion of the E.O gives rise to the

Hertwig’s epithelial root sheath.Hertwig’s epithelial root sheath.















DEVELOPMENTAL DISTURBANCES OFDEVELOPMENTAL DISTURBANCES OFTEETHTEETH

• DISTURBANCES IN SIZE:DISTURBANCES IN SIZE:

- Microdontia- Microdontia

-- MacrodontiaMacrodontia

.. DISTURBANCES IN NUMBER:DISTURBANCES IN NUMBER:

-- AnodontiaAnodontia

-- OligodontiaOligodontia-- Supernumerary TeethSupernumerary Teeth

































DISTURBANCES IN STRUCTURE:DISTURBANCES IN STRUCTURE:

-- Amelogenesis ImperfectaAmelogenesis Imperfecta

-- Dentinogenesis ImperfectaDentinogenesis Imperfecta














• DISTURBANCES IN SHAPE:DISTURBANCES IN SHAPE:

-- GeminationGemination

-- FusionFusion-- ConcrescenceConcrescence

-- DilacerationDilaceration

-- Talon cuspTalon cusp

-- Dens In DenteDens In Dente-- Dens EvaginatusDens Evaginatus

-- TaurodontisnTaurodontisn




































Development of Face-Theory

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