Pre natal dev of face /certified fixed orthodontic courses by Indian dental academy

www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing dental education

PRE –NATAL
DEVELOPMENT OF FACEwww.indiandentalacademy.com

CONTENTS
• INTRODUCTION.
• REVIEW OF GENERAL EMBRYOLOGY.
CELL CYCLE.
REPRODUCTION OF CELLS.
MITOSIS & MEIOSIS.
GAMETOGENESIS.
FERTILIZATION.
• PRE – IMPLANTATION DEVELOPMENT.
• POST – IMPLANTATION DEVELOPMENT.
EMBRYONIC PERIOD (THE NEXT 7 WEEK).
FETAL PERIOD (THE NEXT 7 CALENDAR MONTH).

• ORIGIN & MIGRATION OF NEURAL CREST
CELLS.
• PHARYNGEAL ARCHES & ITS DERIVATIVES.
• PHARYNGEAL POUCHES & ITS DERIVATIVES.
• ECTODERMAL CLEFTS & ITS DERIVATIVES.
• FORMATION OF FACE.
• MOLECULAR REGULATION OF FACIAL
DEVELOPMENT.
• DEVELOPMENT OF FACIAL SKELETON
• CONCLUSION.
• REFERENCES.

INTRODUCTION
THE MOBILE MASK IN FRONT OF HUMAN BRAIN
BEGAN TO ATTRACT OUR ATTENTION WHEN WE
WERE BABIES AND CONTINUES TO FASCINATE US
AS LONG AS WE LIVE
W. K. GREGORY, OUR FACE FROM FISH TO
MAN.

WITHIN THE TEXT OF THE CRANIOFACIAL
EMBRYOLOGY,WE COME ACROSS TWO TERMS
GROWTH & DEVELOPMENT.
WHAT DOES THE TERM GROWTH IMPLIES TO US ?
CHANGE IN MAGNITUDE.
DOES IT EXPLAIN TO HOW FAR IT HAPPENS?
WHY SHOULD IT HAPPEN IN A PREDETEMINED
DIRECTION?

TO UNDERSTAND THIS ,THE MORE DESCRIPTIVE &
EXPLANATORY TERM ,DEVELOPMENT IS ADDED.
DEVELOPMENT CONNOTES A MATURATIONAL
PROCESS INVOLVING PROGRESSIVE
DIFFERENTATION AT THE CELLULAR & TISSUE
LEVELS,THERE BY FOCUSING ON THE ACTUAL
BIOLOGICAL MECHANISM THAT ACCOUNTS FOR
OVERALL GROWTH.

• WHAT IS COMPOSITE EQUILIBRIUM?
• IT IS A CHANGING MORPHOLOGIC EQUILIBRIUM,
WHICH RECYCLES THROUGHOUT THE LIFE CYCLE
OF AN INDIVIDUAL.
• IS IT SO IMPORTANT FOR US TO KNOW THE
PRE -NATAL DEVELOPMENT OF FACE.
• HOW IS IT RELATED TO THE FIELD OF
ORTHODONTICS ?

MAL-OCCLUSION OR OTHER DYSPLASIA (INCLUDING
CONGENITAL MALFORMATIONS), ALTHOUGH
CLINICALLY ABNORMAL,IS NONETHLESS IN A
BALANCED STATE.
CLINICAL TREATMENT CAN DISTURB THIS STATE OF
STRUCTURAL & FUNCTIONAL EQUILIBRIUM,AND A
NATURAL REBOUND CAN FOLLOW.
TO KNOW THIS ,EACH OF US SHOULD KNOW HOW
DEVELOPMENT OF FACE PROCCEDS WITHOUT
ANY GREAT VARIATIONS.

CELL CYCLE
• IS THAT PERIOD OF TIME BETWEEN THE BIRTH OF
A CELL, AS A RESULT OF THE DIVISION OF ITS
PARENT CELL, AND ITS OWN DIVISION TO
PRODUCE TWO DAUGHTER CELLS.
• IN EMBRYONIC CELLS IT LASTS FOR ABOUT 1-2hrs
& IN ADULT CELLS LONGER THAN 12hrs.
• THE CYCLE IS DIVIDED INTO 4 DISTINCT PHASES
G1, S, G2 & M PHASE.
• THE COMBINATION OF G1, S & G2 PHASES IS
KNOWN AS INTERPHASE.

PHASES OF CELL CYCLE
• G1 PHASE.
DECIDES TO DIVIDE OR NOT.
GENERATION OF METABOLITES.
GO PHASE.
INDUCTIVE INFLUENCE OF
GROWTH FACTORS .
ROLE OF ONCOGENES.
• S PHASE
REPLICATION OF DNA.
• G2 PHASE
BREAK DOWN OF NUCLEAR
ENVELOPE.
CHROMOSOME CONDENSATION.

• WHAT REGULATES THE TRANSITIONS BETWEEN
THE CELL CYCLE PHASES ?
• MAXIMUM ABUNDANCE OF CYCLINS IN THE CELL
BETWEEN G1 & S PHASE, G2 & M PHASE.
• ACTIVATION OF PROTEIN KINASE ENZYMES
CALLED P34.
• IDENTIFICATION OF TARGET PROTEINS.

REPRODUCTION OF CELLS
• AS THE BODY GROWS IN SIZE MOST CELLS UNDER
GO REPEATED DIVISION.
• SOME CELLS LOSE THE ABILITY TO UDER GO
DIVISION LIKE NEURONS,WHERE AS IN STEM
CELLS IT MAY PERSIST, LIKE HAEMOPOETIC
TISSUE OF BONE MARROW.
• DURING EARLY EMBRYONIC LIFE, CONTROL
APPEARS TO BE LOCAL INVOLVING,THE DIFFUSION
OF METABOLITES.
• AT LATER STAGES,ENDOCRINE CONTROL COMES
INTO PLAY.

TYPES OF CELL DIVISION
• MITOSIS OCCURS IN MOST SOMATIC CELLS.
• MEIOSIS, OCCURS BEFORE FINAL PRODUCTION OF
GAMETES.
• NO OF CHROMOSOMES IS REDUCED TO HALF ,SO
THAT AT FERTILIZATION THE DIPLOID NO IS
RESTORED.
• REASSORTMENT OF GENES, THE ESSENCE OF
EVOLUTION.
• MITOSIS & MEIOSIS DIFFERS CHIEFLY IN
CHROMOSOMAL BEHAVIOUR.
• IN MEIOSIS TWO DIVISIONS OCCUR IN QUICK
SUCCESSION,
UNLIKE MITOSIS (MEIOSIS I,HETEROTYPICAL DIVISION)
LIKE MITOSIS (MEIOSIS II,HOMOTYPICAL DIVISION)

MITOSIS

MEIOSIS

GAMETO GENESIS
• SEXUAL REPRODUCTION IS FOUND THROUGHOUT
THE ANIMAL KINGDOM.
• THE MALE GONAD OR TESTIS PRODUCES MANY
SMALL MOTILE GAMETES OR SPERMATAZOA,
WHICH CONSISTS OF HAPLOID NO OF
CHROMOSOMES.
• IN CONTRAST THE FEMALE GONAD OR OVARY
PRODUCES FEWER, LARGER, NON MOTILE OVA
(EGGS), WHICH ALSO CONSISTS OF HAPLOID NO
OF CHROMOSOMES.

• APPEARANCE OF GERM
CELLS IN THE WALL OF
YOLK SAC.
• MIGRATION OF THESE
CELLS TO THE
DEVELOPING GONADS.
• GERM CELLS UNDERGO
GAMETOGENESIS.
MEIOSIS TO REDUCE THE
NO OF CHROMOSOMES
CYTODIFERENTATION OF
THESE CELLS TO
COMPLETE MATURATION.

OOGENESIS

• BY 5th
MONTH OF PRENATAL
DEVELOPMENT,THE TOTAL NO OF GERM
CELLS IS ESTIMATED TO BE 7 MILLION.
• AT THIS TIME CELL DEATH BEGINS.
• ALL SURVIVING PRIMARY OOCYTES HAVE
ENTERED THE 1ST
MEIOTIC DIVISION.
• PRIMARY OOCYTE ,TOGETHER WITH ITS
SUUROUNDING FLAT EPITHELIAL CELLS,IS
KNOWN AS A PRIMORDIAL FOLLICLE.

MATURATION OF OOCYTES
• ROLE OF OOCYTE MATURATION
INHIBITOR, SECRETED BY
FOLLICULAR CELLS.
• ON ONSET OF PUBERTY,
PRIMORDIAL FOLLICLES BEGIN TO
MATURE .
• IN EACH OVARIAN CYCLE ,ONLY
ONE FOLLICLE REACHES FULL
MATURITY.

• CHANGE IN THE ORIENTATION OF THE
FOLLICULAR CELLS FROM FLAT TO CUBOIDAL.
• PROLIFEATION OF THESE CELLS TO PRODUCE A
STRATIFIED EPITHELIUM OF GRANULOSA CELLS.
• SECRETION OF GLYCOPROTEIN FROM
GRANULOSA CELLS ON THE SURFACE OF THE
OOCYTE FORMING THE ZONA PELLUCIDA.
• THE FOLLICLE IS NOW KNOWN AS PRIMARY
FOLLICLE

• APPEARANCE OF FLUID
FILLED SPACES BETWEEN
GRANULOSA CELLS.
• COALESCENCE OF THESE
SPACES FORMS THE
ANTRUM FORMING THE
SECONDARY FOLLICLE.
• FORMATION OF CUMULUS
OOPHORUS.
• AT MATURITY THE
FOLLICLE MAY BE 10 MM
OR MORE IS KNOWN AS
THE GRAAFIAN FOLLICLE.

SPERMATOGENESIS
AT BIRTH GERM CELLS CAN BE
RECOGNISED IN THE SEX CORDS
OF THE TESTIS.
APPEARANCE OF SUSTENTACULAR
OR SERTOLI CELLS.
SHORTLY BEFORE PUBERTY THE
SEX CORDS ACQUIRE LUMEN &
BECOME THE SEMINIFEROUS
TUBULES.

PRIMORDIAL GERM CELLS
SPERMATOGONIA
TYPE A TYPE B

SPERMIOGENESIS
• TRANSFORMATION OF SPERMATIDS INTO
SPERMATOZOA.
• THESE CHANGES INCLUDE,
FORMATION OF THE ACROSOME.
CONDENSATION OF THE NUCLEI.
FORMATION OF NECK, MIDDLE PIECE,&TAIL.
SHEDDING OF THE MOST OF THE CYTOPLASM.

UNION OF THE GAMETES
• CHARACTERISED BY FUSION OF DISTINCT MALE &
FEMALE GAMETES (SPERM & EGG RESPECTIVELY)
PRODUCED BY DIFFERENT PARENTAL FORMS.
• MAMMALIAN EGGS ARE FERTILIZED ,WHEN THEY
ARE IN SECOND MEIOTIC METAPHASE.
• UNION LEADS TO FERTILIZATION CAUSING THE
CELL DIVISION CELL CYCLE TO RESUME.
• HERE AFTER,CELL DIVISION (SEGMENTATION OR
CLEAVAGE) PROCEEDS WITHIN THE ZONA
PELLUCIDA TO BLASTOCYST STAGE.

• FERTILIZATION OF THE EGG OCCURS IN
THE AMPULLARY REGION OF THE UTERINE.
• SPERMATOZOA IS NOT ABLE TO
FERTILIZE THE OOCYTE IMMEDIATELY
UPON ARRIVAL IN THE FEMALE GENITAL
TRACT BUT MUST UNDERGO,
CAPACITATION.
THE ACROSOME REACTION.

CAPACITATION
• PERIOD OF CONDITIONING IN THE FEMALE
REPRODUCTIVE TRACT.
• EPITHELIAL INTERACTIONS BETWEEN THE
SPERM & MUCOSAL SURFACE OF THE
TUBE.
• REMOVAL OF GLYCOPROTEIN COAT &
SEMINAL PLASMA PROTEINS THAT
OVERLIES THE ACROSOMAL REGION.
• AFTER THIS ,SPERM CELLS CAN PASS
THROUGH THE CORONA CELLS &UNDERGO
ACROSOME REACTION.

ACROSOME REACTION
DIVIDED INTO THREE PHASES,
PHASE 1: PENETRATION OF CORONA
RADIATA.
PHASE 2: PENETRATION OF ZONA
PELLUCIDA.
PHASE 3: FUSION OF THE OOCYTE & SPERM
CELL MENBRANES.

FERTILIZATION PATHWAY

REACTION OF THE EGG AFTER
FERTILIZATION
• CORTICAL & ZONA REACTIONS.
• RESUMPTION OF THE SECOND MEIOTIC
DIVISION.
• METABOLIC ACTIVATION OF THE EGG.
• INTIATION OF THE CLEAVAGE.

PRE - IMPLANTATION DEVELOPMENT
(THE 1ST
7 DAYS)

• AFTER THE TWO CELL STAGE THE ZYGOTE
UNDER GOES SERIES OF MITOTC
DIVISIONS.
• FORMATION OF BLASTOMERES.
• UNTIL THE EIGHT CELL STAGE ,THEY FORM
A LOOSELY ARRANGED CLUMP.

• COMPACTION OF CELLS ,WHICH ARE HELD
TOGETHER BY TIGHT JUNCTIONS.
• THIS PROCESS SEGREGATES INNER CELLS FROM
OUTER CELLS.
• APPROXIMATELY AFTER THREE DAYS OF
FERTILIZATION COMPACTED CELLS DIVIDE TO
FORM A 16 CELL MORULA .
• INNER CELLS OF THE MORULA CONSTITUTE THE
INNER CELL MASS & SURROUNDING CELLS
COMPOSE THE OUTER CELL MASS.
• INNER CELL MASS GIVES RISE TO EMBRYOBLAST
& THE OUTER CELL MASS GIVES RISE TO
TROPHOBLAST, WHICH LATER CONSTITUTES THE
PLACENTA.

UNCOMPACTED CELLS COMPACTED CELLS

BLASTO CYST FORMATION
• BY THE TIME MORULA ENTERS THE
UTERINE CAVITY FLUID BEGINS TO
PENETRATE THROUGH THE ZONA
PELLUCIDA INTO THE INTER CELLULAR
SPACES OF THE INNER CELL MASS.
• THESE SPACES BECOME CONFLUENT TO
FORM A SINGLE CAVITY ,THE BLASTOCELE.
• AT THIS TIME EMBRYO IS A BLASTOCYST.

INNER CELL MASS ARE NOW CALLED THE EMBRYO
BLAST &THOSE OF OUTER CELL MASS ARE
CALLED TROPHOBLAST.
ZONA PELLUCIDA NOW DISAPPEARS TO ALLOW
IMPLANTATION TO BEGIN.
ABOUT THE SIXTH DAY TROPHOBLASTIC CELLS
OVER THE EMBRYOBLAST POLE BEGIN TO
PENETRATE BETWEEN THE EPITHELIAL CELLS OF
THE UTERINE MUCOSA.
IMPLANTATION OF THE ZYGOTE TAKES PLACE AS A
RESULT OF MUTUAL ACTION OF TROPHOBLASTIC
& ENDOMETRIAL CELLS.

SUMMARY OF EVENTS DURING THE 1ST
WEEK OF DEVELOPMENT

POST – IMPLANTATION DEVELOPMENT

EMBRYONIC PERIOD
(THE NEXT 7 WEEKS)
• DIVIDED INTO THREE PERIODS
• PRESOMITE (8 – 21 DAYS)
FORMATION OF GERM LAYERS & FETAL
MEMBRANES.
• SOMITE (21 – 31 DAYS)
FORMATION OF DORSAL METAMERIC
SEGMENTS,BODY SYSTEMS & ORGANS.
• POST SOMITE (32 – 56 DAYS)
FORMATION OF BODYS EXTERNAL FEATURES.

PRESOMITE PERIOD
(8 – 21 DAYS)
• EMBRYONIC DISK IS
COPMOSED OF TWO
PRIMARY GERM
LAYERS.
• ECTO DERM.
• ENDO DERM.

PRE CHORDAL PLATE
• AT THE 14TH
DAY THERE IS AN EARLY DEMARACTION AT THE
ANT. POLE OF THE INTIALLY OVAL DISK.
• AN ENDODERMAL THICKENING APPEARS IN THE FUTURE MID
CEPHALIC REGION, THE PRE CHORDAL PLATE.
PERFORMS HEAD ORGANIZING FUNCTION
PREFACES THE DEVELOPMENT OF THE
OROFACIAL REGION.

PRIMITINE STREAK
• APPEARANCE OF THE THIRD PRIMARY GERM LAYER,THE
MESODERM.
• THE RESULTANT BULGE IN THE DISK IS GROOVED CRANIO
CAUDALLY.
• FROM THE PRIMITIVE STREAK THE RAPIDLY PROLIFERATING
TISSUE KNOWN AS THE MESEN CHYME FORMS THE INTRA
EMBRYONIC MESODERM.

• MIGRATION OF MESENCHYMAL CELLS.
• BILAMINAR DISK IS CONVERTED INTO A
TRILAMINAR STRUCTURE.
• FORMATION OF THE NOTOCHORD BY THE
PROLIFERATION & DIFFERENTATION OF THE
CRANIAL END OF THE PRIMITIVE STREAK.

NOTOCHORD
• TERMINATES ANTERIORLY AT THE PRE
CHORDAL PLATE.
• SERVES AS THE AXIAL SKELETON OF THE
EMBRYO.
INDUCES FORMATION OF THE NEURAL PLATE IN
THE OVER LYING ECTODERM (NEURAL
ECTODERM)
LATERAL MESODERM WHICH INDUCES EPIDREMAL
DEVELOPMENT(CUTANEOUS ECTODERM).

DERIVATIVES OF THE THREE PRIMARY
GERM LAYERS
• ECTODERM
CUTANEOUS STRUCTURES & NEURAL SYSTEMS.
• MESODERM
CARDIOVASCULAR SYSTEM ,THE LOCOMOTOR
SYSTEM, CONNECTIVE TISSUES & DENTAL PULP.
• ENDODERM
LINING EPITHELIUM OF THE RESPIRATORY TRACT
& ALIMENTARY CANAL,SECRETORY CELLS OF THE
LIVER &PANCREAS.

ABOUT 20 DAYS THE NEURAL PLATE ECTODERM UNDER GOES
INFOLDINGS ALONG THE MIDLINE FORMING THE NEURAL
FOLDS.
INFOLDING OF THE NEURAL FOLDS CREATE NEURAL GROOVE.
ABOUT 22 DAYS THE NEURAL FOLDS FUSE ,IN THE SITE OF THE
FUTURE OCCIPITAL REGION.
THIS INTIAL CLOSURE PROCEEDS BOTH CEPHALICALLY &
CAUDALLY TO FORM THE NEURAL TUBE.
THIS NEURAL TUBE IS SUBMERGED BENEATH THE
SUPERFICIAL COVERING OF THE CUTANEOUS ECTODERM

THE SOMITE PERIOD
(21 – 31 DAYS)
• CHARACTERISED BY FOLDINGS &
STUCTURING.
• CONVERSION OF THE EMBRYONIC DISK
INTO A TUBULAR STRUCTURE.
• DEVELOPMENT OF THE BRAIN & SPINAL
CORD FROM THE NEURAL PLATE.

DEVELOPMENT OF MESODERM INTO
THREE AGGREGATIONS

ORGANIZATION OF PARAXIAL
MESODERM INTO A NO OF
SEGMENTS.
EACH SOMITE DIFFERENTIATES
INTOTHREE PARTS.
SCLEROTOME
DERMATOME
MYOTOME
SOMITE PERIOD IS
CHARACTERIZIED BY
ESTABLISHMENT OF MOST OF
THE ORGAN SYSTEMS.

POST SOMITE PERIOD
(32 -56 DAYS)
• CHARACTERIZIED BY FADING OF THE
PREDOMINANT SEGMENTED SOMITES.
• HEAD DEVELOPMENT DOMINATES THIS
PERIOD.
• RECOGNITION OF FACIAL FEATURES.
• EMBRYO AT THE END OF THIS PERIOD IS
TERMED FETUS.

FETAL PERIOD
(THE NEXT 7 CALENDAR MONTH)
• RAPID GROWTH & REPROPORTIONING OF BODY
COMPONENTS.
• LITTLE FURTHER ORGANOGENESIS OR TISSUE
DIFFERENTIATION.
• BODY GROWS RAPIDLY AS COMPARED TO THE
PRECOCIOUS GROWTH & DEVLOPMENT OF HE
HEAD.
• AT 4TH
MONTH OF INTRA UTERINE LIFE THE FACE
ASSUMES A HUMAN APPEARANCE.

ORIGIN & MIGRATIN OF NEURAL CREST
CELLS

• UNDER THE INDUCTIVE INFLUENCE OF THE
NOTOCHORD,THE NEURAL PLATES UNDERGO INFOLDING
TO FORM THE NEURAL TUBE.
• INFOLDING OF THE NEURAL TUBE FORMS NEURAL FOLDS
FROM WHERE THESE SPECIAL GROUP OF CELLS ARISE.
• FORMED FIRST IN THE ANGLE BETWEEN THE DEVELOPING
NEURAL TUBE & THE ECTODERMAL SHEET THAT COVERS
THE DORSUM OF THE EMBRYONIC DISC.
• INTIAL MIGRATION OF THESE CELLS IS PROBABLY 19-38
DAYS AFTER FERTILIZATION.

• THESE CELLS MIGRATE THROUGH CELL FREE SPACES
BENEATH THE SURFACE ECTODERM.
• MIGRATION OF THESE CELLS IS NOT RANDOM, BUT
FOLLOWS A DEFINITE PATTERN,BOTH SPATIALLY
&TEMPORALLY.
• WHAT GUIDES THESE CELLS ?
DISRUPTION OF THE ECTODERMAL MEMBRANE.
COMBINATION OF NEUROTROPHISM.
CLEAVAGE PLANES.
SUCCESION OF MICROENVIRONMENT.
DIFFERENTIAL GROWTH OF CELLS.
MORPHOGENIC TISSUE INTERACTION.www.indiandentalacademy.com

THE TWO PRINCIPAL SOURCES OF MESENCHYME IN HEAD ARE
THE PARAXIAL MESODERM & THE NEURAL CREST CELLS.
CEPHALIC NEURAL CREST CELLS ARE PARTICULARILY
IMPORTANT IN THE FORMATION OF THE FACIAL PART OF
THE SKULL.
THESE CELLS MIGRATE BOTH IN FRONT & BEHIND THE
DEVELOPING EYE TO REACH THE PREDETERMINED SITES
FACIAL SWELLINGS.
MIGRATION IS ASSITED BY HYALURONATE RICH
FIBRONECTIN,COLLAGEN,CHONDRITIN SULFATE
&GLYCOAMINOGLYCANS.
THE DISTRIBUTION & CONCENTRAION OF THESE PRODUCTS
VARIES ALONG THE MIGRATION ROUTE.

BREAK

• PHARYNGEAL ARCHES & ITS DERIVATIVES.
• PHARYNGEAL POUCHES & ITS DERIVATIVES.
• ECTODERMAL CLEFTS & ITS DERIVATIVES.
• FORMATION OF FACE.
• MOLECULAR REGULATION OF FACIAL
DEVELOPMENT.
• DEVELOPMENT OF FACIAL SKELETON
• CONCLUSION.
• REFERENCES.

PHARYNGEAL ARCHES

• APPEARS DURING THE 4th
& 5th
WEEK OF INTRA UTERINE
DEVELOPMENT.
• CONSISTS OF BARS OF MESENCHYMAL TISSUE SEPARATED
BY DEEP CLEFTS KNOWN AS PHARYNGEAL (BRANCHIAL)
CLEFTS.
• ON DEVELOPMENT, A NO OF OUT POCKETING APPEARS,
ALONG THE LATERAL WALLS OF THE PHARYNGEAL GUT
WHICH ARE THE PHARYNGEAL POUCHES.
• CONTRIBUTE NOT ONLY TO THE FORMATION OF THE NECK
BUT ALSO PLAY AN IMPORTANT ROLE IN THE FORMATION OF
THE FACE.

THOUGH DEVELOPMENT OF THESE ( ARCHES, CLEFTS &
POUCHES ) RESEMBLES FORMATION OF GILLS IN FISHES &
AMPHIBIA,IN THE HUMAN EMBRYO REAL GILLS ARE NEVER
FORMED. THEREFORE THE TERM PHARYNGEAL ARCHES HAS
BEEN ADOPTED.

FRONTAL VIEW OF EMBRYO AT 4- 4half
WEEKS.

FIRST PHARYNGEAL ARCH

SECOND PHARYNGEAL ARCH

THIRD PHARYNGEAL ARCH

FOURTH & SIXTH PHARYNGEAL ARCH

PHARYNGEAL POUCHES
• THE HUMAN EMBRYO HAS FIVE FIVE PAIRS OF PHARYNGEAL
POUCHES.
• THE LAST ONE IS ATYPICAL AND OFTEN CONSIDERED AS
PART OF THE FOURTH.
• SINCE THE EPITHELIAL ENDODERMAL LINING OF THE
POUCHES GIVES RISE TO A NO OF IMPORTANT ORGANS, THE
FATE OF EACH POUCH IS CONSIDERED SEPARATELY.

FIRST PHARYNGEAL POUCH

SECOND PHARYNGEAL POUCH

THIRD PHARYNGEAL POUCH

FOURTH PHARYNGEAL POUCH

FIFTH PHARYNGEAL POUCH

PHARYNGEAL CLEFTS

FORMATION OF THE FACE

THE FACIAL PROMINENCES

• FACIAL PROMIENCES ARE DERIVED FROM THE NEURAL
CREST ECTOMESENCHYME.
• FRONTO NASAL PROMIENCES, WHICH SURROUNDS THE
FOREBRAIN,SPROUTS LATERAL OPTIC DIVERTUCLA THAT
FORMS THE EYES.
• THE PORTION BETWEEN THE EYES FORM THE FOREHEAD.
• AT THE INFEROLATERAL CORNERS ,ECTODERMAL
THICKENINGS APPEAR,THE NASAL (OLFACTORY) PLACODES.
• THIS IS INDUCED BY THE UNDERLYING OLFACTORY NERVES.

• DURING 5TH
WEEK THE NASAL PLACODES INVAGINATE TO
FORM THE NASAL PITS,WHICH ARE THE PRECURSORS OF
THE ANTERIOR NARES.
• THIS CREATES A RIDGE OF TISSUE THAT SURROUNDS EACH
PIT AND FORMS THE NASAL PROMINENCES.
• THE PROMINENCES ON TNE OUTER EDGES OF THE PITS ARE
THE LATERAL NASAL PROMINENCES & THOSE ON THE INNER
EDGE ARE THE MEDIAN NASAL PROMINENCES.

5TH
WEEK EMBRYO

UNION OF THE FACIAL PROMINENCES
• THIS OCCURS BY TWO DEVELOPMENTAL EVENTS AT
DIFFERENT LOCATIONS.
• MERGING OF THE FRONTONASAL,MAXILLARY & MANDIBULAR
PROMINENCES.
MERGING TAKES PLACE AS A RESULT OF MIGRATION INTO &
OR PROLIFERATION OF UNDERLYING MESENCHYME INTO
THE GROOVE.
• FUSION OF THE CENTRAL MAXILLONASAL COMPONENTS.
TAKES PLACE BY DISINTEGRATION OF THEIR CONTACTING
SURFACE EPITHELIA , ALLOWING INTER - MINGLING OF THE
UNDER LYING MESENCHYME.

• DURING THE NEXT TWO WEEKS ,THE MAXILLARY
PROMINENCES CONTINUES TO INCREASE IN THE SIZE.
• GROWS MEDIALLY, COMPRESSING THE MEDIAL NASAL
PROMINENCES TOWARDS THE MID LINE.
• SUBSEQUENTLY THE CLEFT BETWEEN THEM IS LOST AND
THEY FUSE.
• FUSION OF THE MEDIAN NASAL & MAXILLARY PROMINENCES
PROVIDES CONTINUITY OF THE UPPER JAW & THE LIP.
• MID LINE MERGING OF THE MEDIAN NASAL PROMINENCES
FORMS THE MEDIAN TUBERCULUM & PHILTRUM OF THE
UPPER LIP,THE TIP OF THE NOSE &THE PRIMARY PALATE.

7TH
WEEK EMBRYO

• THE LOWER JAW & LIP ARE FORMED BY MIDLINE MERGING
OF THE PAIRED MANDIBULAR PROMINENCES.
• COMMISURES (CORNERS) OF THE MOUTH ARE FORMED BY
THE LATERAL MERGING OF THE MAXILLARY & MANDIBULAR
PROMINENCES.

CHANGE IN THE BLOOD SUPPLY OF THE FACE
DURING THE 7TH
WEEK

NASO LACRIMAL DUCT
• PRESENCE OF DEEP
FURROW.
• MIGRATION OF EPITHELIAL
CELLS INTO THE
MESENCHYME.
• CANALIZATION OF THESE
CORDS TO FORM THE
NASO LACRIMAL DUCT.
• UPPER END WIDENS TO
FORM THE LACRIMAL SAC.
• DUCT BECOMES PATENT
ONLY AFTER THE BIRTH.
7TH
WEEK EMBRYO

EYES
• ON THE VENTROLATERAL ASPECT
OF THE DEVELOPING FORE BRAIN ,
ECTODERMAL THICKENINGS
APPEAR AS LENS PLACODE.
• THE LENS PLACODE SINKS BELOW
THE SURFACE EPITHELIUM & IS
EVENTUALLY CUT OF FROM THE
SURFACE ECTODERM FORMING
THE LENS VESICLE.

• AT THIS TIME THE DEVELOPING EYE BALL PRODUCES
SIGNIFICANT BULGING .
• THESE BULGINGS ARE FIRST DIRECTED LATERALLY.
• DUE TO ENORMOUS GROWTH OF THE CEREBRAL
HEMISPHERES THE EYES MIGRATE MEDIALLY.
• LATER THE EYE LIDS ARE FORMED FROM THE SURFACE
ECTODERM.
• EYE LIDS REMAIN FUSED UNTIL THE 7TH
MONTH OF INTRA
UTERINE LIFE & THEN INVADING MUSCLES ALLOWS THEIR
OPENING.

• FORMED FROM THE DORSAL
PART OF THE 1ST
ECTODERMAL
CLEFT.
• APPEARANCE OF SERIES OF
MESODERMAL THICKENINGS
OFTEN CALLED TUBERCLES OR
HILLOCKS.
• FORMATION OF PINNA BY FUSION
OF THESE THICKENINGS.
• WHEN INTIALLY FORMED ARE AT
THE NECK REGION BUT WITH THE
DEVELOPMENT OF MANDIBLE
THEY ASCEND TO THE SIDE OF
THE HEAD AT THE LEVEL OF THE
EYES.
EARS

NOSE
• FORMED BY COMPLEX CONTRIBUTION
FROM THE
FRONTAL PROMINENCE (THE BRIDGE)
THE MERGED MEDIAN NASAL PROMINENCES (THE MEDIAN
RIDGE & THE TIP)
THE LATERAL NASAL PROMINENCES (THE ALAE)
CARTILAGINOUS NASAL CAPSULE (THE SEPTUM & NASAL
CONCHAE)

MOLECULAR REGULATION OF FACIAL
DEVELOPMENT

ARRANGEMENT OF GENES

EXPRESSION OF THE HOXB CLUSTER
OF HOMEOBOX GENES

HOX GENE EXPRESSION IN RHOMB MERES
OF THE HIND BRAIN

SKELETAL SYSTEM
SKULL
NEURO CRANIUM
• THE MEMBRANOUS PART
• THE CARTILAGINOUS PART
OR CHONDROCRANIUM
VISCERO CRANIUM
• BONES OF THE FACE.
• FORMED FROM THE FIRST
TWO PHARYNGEAL ARCHES

MEMBRANOUS NEUROCRANIUM

CARTILAGINOUS NEUROCRANIUM OR
CHONDROCRANIUM

DEVELOPMENT OF FACIAL SKELETON
• THE FACE MAY BE CONVIENTLY,IF SOME WHAT ARBITARILY
DIVIDED INTO UPPER, MIDDLE & LOWER THIRDS.
• THE THREE PARTS CORRESPOND GENERALLY TO THE
EMBRYONIC STRUCTURES NAMELY THE FRONTO NASAL,
MAXILLARY & MANDIBULAR PROCESS.

• UPPER THIRD OF FACE IS PREDOMINANTLY OF
NEUROCRANIAL COMPOSITION,WITH THE FRONTAL BONE OF
THE CALVARIA ,PRIMARILY RESPONSIBLE FOR THE FORE
HEAD.
• INTIALLY GROWS MOST RAPIDLY KEEPING PACE WITH ITS
NEUROCRANIAL ASSOCIATION & THE PRECOCIOUS
DEVELOPMENT OF THE FRONTAL LOBES OF THE BRAIN.
• ACHIEVES ITS ULTIMATE GROWTH POTENTIAL AT AN EARLY
AGE, PRACTICALLY CEASING THE GROWTH SIGNIFICANTLY
AFTER THE 12 YEARS OF LIFE.

• MIDDLE THIRD OF FACE IS SKELETALLY THE MOST
COMPLEX,BEING COMPOSED IN PART OF THE CRANIAL BASE
& INCORPORATING BOTH THE NASAL EXTENSIONS OF THE
UPPER THIRD PART OF THE MAXILLARY APPARATUS.
• GROWS MORE SLOWLY OVER A PROLONGED PERIOD, NOT
CEASING THE GROWTH UNTIL THE LATE ADOLESENCE.

• THE LOWER THIRD OF FACE COMPLETES THE MASTICATORY
APPARATUS, BEING COMPOSED OF THE SKELETON OF THE
MANDIBLE & ITS DENTITION.
• GROWS MORE SLOWLY , NOT CEASING THE GROWTH UNTIL
THE LATE ADOLESENCE.

• FACIAL BONES DEVELOP INTRA MEMBRANOUSLY FROM
OSSIFICATION CENTERS IN THE NEURAL CREST MESENCHYME OF
THE EMBRYONIC FACIAL PROCESS.
• IN THE FRONTONASAL PROCESS,INTRAMEMBRANOUS SINGLE
OSSIFICATION CENTER APPEARS IN THE 3RD
MONTH.
• DURING 8TH
WEEK A PRIMARY OSSIFICATION CENTER APPEARS FOR
EACH MAXILLA AT THE TERMINATION OF INFRA ORBITAL NERVE
JUST ABOVE THE CANINE TOOTH DENTAL LAMINA.
• FURTHER TWO INTRA MEMBRANOUS PREMAXILLARY CENTERS
APPEAR ANTERIORLY ON EACH SIDE IN THE 8TH
WEEK & RAPIDLY
FUSE WITH THE PRIMARY MAXILLA.
• THE MANDIBULAR PROCESS DEVELOP BILATERALLY FROM A
SINGLE INTRA MEMBRANOUS CENTRE.

THE ATTACHEMENT OF THE FACIAL SKELETON ANTERO –
INFERIORLY TO THE CALVARIA DETERMINES THE CHONDRO
CRANIAL INFLUENCE ON FACIAL GROWTH.

CONCLUSION
JUST AS THE CLINICIAN NEEDS THE MEDICAL
HISTORY TO MAKE A LOGICAL DIAGNOSIS, SO TOO
THE GROWTH AND DEVELOPMENT OF FACE IS
ESSENTIAL FOR A LOGICAL EXPLANATION OF
ANY STRUCTURAL AND FUNCTIONAL
IMBALANCES IF IT DO OCCURS.

REFERENCES
• SPERBER EMBRYOLOGY.
• LANGMANS EMBRYOLOGY - 8TH
EDITION.
• GRAYS ANATOMY – 38TH
EDITION.
• FUNDAMENTALS OF CRANIOFACIAL GROWTH – Edited by
ANDREW D. DIXON.
• CONTEMPORARY ORTHODONTICS – 3RD
EDITION Edited by
WILLIAM R.PROFFIT.
• HAND BOOK OF ORTHODONTICS – 4TH
EDITION Edited by
ROBERT E MOYERS.
• ORTHODONTICS,PRINCIPLES & PREVENTION – Edited by J A
SALZMANN.
• ESSENTIALS OF FACIAL GROWTH – ENLOW & HANS.

THANK YOU
For more details please visit

Pre natal dev of face /certified fixed orthodontic courses by Indian dental academy

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

Similaire à Pre natal dev of face /certified fixed orthodontic courses by Indian dental academy

Similaire à Pre natal dev of face /certified fixed orthodontic courses by Indian dental academy (20)

Plus de Indian dental academy

Plus de Indian dental academy (20)

Dernier

Dernier (20)

Pre natal dev of face /certified fixed orthodontic courses by Indian dental academy