PRE-NATAL
GROWTH
&
DEVELOPMENT
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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 What is EMBRYOLOGY?
Embryology is the study of prenatal development
of embryo and fetuses.
 SIGNIFICANCE OF EMBRYOLOGY
...
 Period of ovum- fertilization to 2 weeks
 Period of embryo – 2nd to 8th week
 Period of fetus - 9th week to term
Imp-w...
He who sees things grow from the
beginning will have the finest view of
them……..
-ARISTOTLE
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Day 0
FERTILIZATION
Human development begins at fertilization, the process
during which a male sperm unites with a female ...
Zygote-contains
chromosomes and genes
that are derived from both
mother and father.
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THE FIRST WEEK
 CLEAVAGE OF ZYGOTE:
-Cleavage usually occurs as the
zygote passes along the uterine
tube.
-Cleavage consi...
Day 1-3
 Cleavage
 blastomeres
 morula
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2 cell 4 cell 8 cell
REF-THE DEVELOPING HUMAN, MOORE AND PERSAUDwww.indiandentalacademy.com
FORMATION OF BLASTOCYST
 As morula enters uterus, a fluid-filled space called
blastocyst cavity appears in morula.
 As f...
Implantation
 6 days after
fertilization, blastocyst
adheres to endometrial
surface.
 As soon as it attaches, the
tropho...
Implantation
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 Implantation of blastocyst
commences at the end
of 1st week and completed
by end of 2nd week.
 The syncytiotrophoblast
...
DAY 9
 Isolated cavities
called lacunae
appear in
syncytiotrophoblast
 Adjacent lacunae
fuse to form lacunar
networks
Ca...
 Syncytiotrophoblast
erodes sinusoids
and maternal blood
flows freely In
lacunar networks
 Communication with
eroded end...
 Site at which blastocyst EMBRYONIC POLE.
gets implanted
CLINICAL RELEVANCE
Syncytiotrophoblast releases HUMAN CHORIONIC
...
FORMATION OF AMNIOTIC CAVITY, EMBRYONIC
DISC AND YOLK SAC:
 As implantation of blastocyst progresses, a small cavity
appe...
 So now there are 2 cavities:
1. “AMNIOTIC CAVITY” (above)
2. “PRIMARY YOLK-SAC” (below - later forms secondary yolk
sac)...
 Defect in endometrium persists for 2 days- filled by a closing
plug- fibrinous coagulum of blood.
 In extra-embryonic m...
DAY 14
2 processes occur
simultaneously:
Formation of
extraembryonic somatic
and splanchnic mesoderm
due to split of
extr...
 Defect in endometrium
disappears
 Cells from hypoblast
migrate along inside of
Primary yolk sac –
pinched off and small...
DAY 14
The amniotic cavity (epiblast
at floor)
and secondary yolk sac
(hypoblast at roof)
resembles 2 balloons
pressed tog...
DAY 14
Epiblastic cells- formation of primitive streak
Hypoblastic cells in a localized area are now columnar and
form a t...
THE THIRD WEEK
 GASTRULATION : is a formative process by
which the 3 germ layers & axial orientation are
established in t...
 GASTRULATION:
 the Bilaminar embryonic disc is converted to a
Trilaminar embryonic disc.
 It is the beginning of morph...
PRIMITIVE STREAK:
 It results from
proliferation and
migration of the cells of
epiblast to the median
plane of the embryo...
As soon as the primitive streak appear, it is possible to identify
the embryo‟s
Cranio -caudal axis
Primitive groove deve...
FATE OF PRIMITIVE STREAK
 Normally the primitive streak undergoes
disappears by the end of fourth week.
 Remnants of pri...
Fetal Alcohol Syndrome
 clinically described 30 years ago (1973),
caused by maternal alcohol consumption during pregnancy...
Fetal Alcohol SyndromeFAS
•Maternal alcoholism causes effects of 2 types
•In moderation i.e. 1-2 ounces/day (30ml) can cau...
FAS
CHARACTERISTICS:
Microcephaly - leads to small head
circumference
Palpebral fissure - short opening
of eye
Epicanthal ...
 MANAGEMENT:
 early intervention is critical to determine prognosis for a
child with FAS
 earlier provision of medical,...
 FORMATION OF GERM
LAYERS:
 Soon after primitive streak
appears, cells leave its
deep surface and migrate
to form a loos...
 the mesenchyme forms a
layer called Intraembryonic
mesoderm.
 Some cells of the Epiblast
displace the Hypoblast
forming...
 All the above cells have
the potential to
proliferate and
differentiate into diverse
types of cells, such as
fibroblast,...
DERIVATIVES OF GERM LAYERS
 ECTODERM: Epidermis, hair, nail.
Central and peripheral nervous system.
Mammary, pituitary an...
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FORMATION OF NOTOCHORD
 Some mesenchymal cells
migrate cranially from the
primitive node and
pit, forming a median
cellul...
 The notochordal process cannot extent
beyond the prechordal plate.
 Place of fusion of upper ectoderm and
lower endoder...
prochordal plate
Notochordal canal
cloacal membrane
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IMPORTANCE OF NOTOCHORD:
 Defines primordial axis of embryo and gives
rigidity.
 Serves as basis for development of axia...
NEURULATION
 Formation of neural plate and neural folds and closure
of these folds to form the neural tube constitute
Neu...
 Neural plate formation is induced by developing
notochord.
 The ectoderm of neural plate called Neuroectoderm
gives ris...
NEURULATION
 At about 18th day, the neural plate invaginates along
its central axis to form median “Neural
groove”, which...
 The neural fold are the first signs of brain
development.
 By the end of 3rd week the neural folds begin to move
togeth...
NEURAL CREST FORMATION
 As the neural folds
fuse to form the neural
tube, some
neuroectodermal cells
lying along the cres...
 Soon it forms a flattened irregular mass, the neural
crest, between the neural tube and the overlying surface
ectoderm.
...
 CREST CELLS DERIVATIVES.
 Neurolemmal sheath of peripherl nerves.
 Meningeal coverings of the brain and the
spinal cor...
 NEURAL TUBE DEFECTS- primarily
results from failure of neural folds to fuse
and form the neural tube in the brain
region...
Development of somites
 As the notochord and neural tube
form,intraembryonic mesoderm on each
side proliferates to form a...
Development of somites DAYS 20-30
•Paraxial mesoderm
differentiates into paired
cuboidal bodies- somites
•First appear in ...
4th week
onwards...
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 Paraxial mesoderm.
 Lateral plate mesoderm.
 Neural crest cells .
 Ectodermal placodes
Mesenchyme for formation of he...
PHARYNGEAL APARATUS
 “Branchial”- branchia, gill
resemblance to fish embryo
 - Pharyngeal arches (mesoderm)
 - Pharynge...
PHARYNGEAL ARCHES
 Pharyngeal arches consist of core of mesenchymal tissue
covered on the outside by surface ectoderm and...
 By the end of the 4th week , 4 pairs of pharyngeal
arches are visible externally as rounded ridges on
each side of the f...
Each arch is characterized by its own
 Cartilaginous rod that forms the skeleton of the arch
 muscular component
 nerve...
DERIVATIVES OF PHARYNGEAL
Apparatus
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SKELETAL DERIVATIVES
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MUSCLE DERIVATIVES
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NERVE SUPPLY
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ARTERIAL SUPPLY
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 The first pharyngeal arch is often called the mandibular arch.
 First arch splits giving rise to 2 regions:
- cranial p...
MAXILLARY PROCESS:
mesenchyme of the maxillary
process gives rise to
 premaxilla,
 maxilla,
 zygomatic bone and
 part ...
MANDIBULAR
PROCESS:
Cartilage of the 1st arch
is meckel‟s cartilage.
Dorsal end-ossifies to
form malleus and incus
Mid...
Meckle‟s cartilage
 Ventral part-forms horse shoe shaped structure in the
shape of future mandible and has close position...
 MUSCULATURE:
 Temporalis
 Masseter
 Pterygoids
 Anterior belly of digastric
 Mylohyoid
 Tensor tympani
 Tensor pa...
NERVE SUPPLY:
 Nerve supply to muscles
of the 1st arch is by
mandibular branch of
trigeminal nerve.
 Sensory supply to t...
 Called the hyoid
arch as part of the
hyoid bone develops
here
 The cartilage of 2nd
arch is called as
Reichert‟s cartil...
 It gives rise to,
 Stapes
 Styloid process of
temporal bone
 Stylohyoid ligament
 Lesser horn and
upper part of body...
MUSCLES:
 Stepedius.
 Posterior belly of
digastric.
 Auricular.
 Muscles of facial
expression
SECOND PHARYNGEAL ARCH
w...
NERVE:
 Facial nerve supplies
all these muscles.
SECOND PHARYNGEAL ARCH
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CARTILAGE of 3rd
pharyngeal arch
produces,
 Lower part of body of
hyoid bone.
 Greater horn of hyoid
bone.
THIRD PHARYNG...
MUSCLE:
 Stylopharyngeus
muscle.
NERVE:
 Glossopharyngeal
nerve.
THIRD PHARYNGEAL ARCH
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CARTILAGINOUS
component of 4th and 6th
pharyngeal arches fuse
to form,
 Thyroid cartilage.
 Cricoid cartilage.
 Aryteno...
MUSCLES:
4th arch:
 cricothyroid,
 levator palatini,
 constrictors of pharynx ,
6th arch:
 intrinsic muscles of
larynx...
NERVE:
 4TH arch: Superior laryngeal branch of vagus nerve.
 6th arch: Recurrent laryngeal branch of vagus nerve.
FOURTH...
ARTERIAL SUPPLY
 Pharyngeal arch arteries are called aortic arches
 from arch 1 & 2-arteries significantly smaller
 Arc...
 Human embryo has 5 pairs of pharyngeal pouches, the last one
is atypical and often considered as part of the 4th pouch.
...
 It comes in contact with the
epithelial lining of the 1st
pharyngeal cleft, which is a
future external auditory meatus.
...
 Buds are secondarily invaded
by mesodermal tissue thus
forming primordium of palatine
tonsil
 3rd and 5th month- tonsil...
3rd and 4th pouches are characterized by ,
 DORSAL WING and VENTRAL WING
In 5th week, from 3rd pouch
 Dorsal wing- Infer...
Both gland primordia lose their connection with pharyngeal
wall, the thymus then migrates in a caudal and medial
directio...
 The primordia finally rest on the dorsal surface of the thyroid
gland and forms inferior parathyroid gland.
 The thymus...
 Of the 4th pouch
Dorsal wing- superior
parathyroid gland.
 It also loses contact with
wall of pharynx and
migrate cauda...
 Last pharyngeal pouch to develop
 Usually considered to be a part of 4th pouch.
 Gives rise to – Ultimobranchial body,...
Derivatives PHARYNGEAL POUCHES
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 located between arches
externally
 these are spaces, thus
contain no germ layer
components
 Four pharyngeal clefts, of...
 Active proliferation of mesenchymal tissue of 2nd arch, results in
overlapping of it over 3rd and 4th arch causing the 2...
Pharyngeal Membranes:
 Appear in the floors of the pharyngeal grooves and form where
the epithelia of the groove & pouche...
 Primordial mouth or stomodeum appears as slight depression
of surface ectoderm
 It is separated from cavity of primordi...
•Ruptures at 26 days
•Communication of primordial cavity and foregut with amniotic
cavity
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CLINICAL COMMENT
Most congenital anomalies in head-
neck region originate during
transformation of the pharyngeal
apparatu...
 BRANCHIAL FISTULAS:
 -an abnormal canal that opens internally into tonsillar sinus and
externally in the side of the ne...
BRANCHIAL CYST:
 Remnants of parts of cervical sinus and/or the
2nd pharyngeal groove may persist and form a
spherical or...
 May develop anywhere
along the anterior border
of SCM muscle
 Slowly enlarging painless
swelling in the neck.
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 NEURAL CREST CELLS:
Essential for formation of craniofacial region but
disruption results in severe craniofacial malform...
TCS
 First described by Thomson and Toynbee in 1846-47
Later, essential components described by Treacher Collins
in 1960
...
Characteristics:
 Fishlike” facial appearance
 Usually bilateral and symmetric expression
 Degree of malformation at bi...
TCS
 “Cleft palate in 35%
 Downward slanting palpebral
fissures
 Retrusive mandible and maxilla
 High mandibular plane...
Treacher Collins syndrome
1. Preoperative frontal view of 16-year-old patient with Treacher
Collins Syndrome. No previous ...
PRS
 Triad of micrognathia, glossoptosis and cleft palate
 First described by St. Hilaire in 1822
 Pierre Robin first r...
 The initiating defect is micrognathia which results in
posterior displacement of the tongue i.e. glossoptosis
and obstru...
 Occurs because the 3rd and 4th pharyngeal pouches fail to
differentiate into thymus and parathyroid glands.
 Congenital...
characteristics
 Congenital hypo-parathyroidism
 Increased susceptibility to infections
 Shortened philtrum of lip
 Lo...
Characteristics
 Maxilla, temporal,& zygomatic bones are reduced in size and
flattened.
 Facial asymmetry
 Ear, eye, an...
Preoperative frontal view of 17-year-old patient after
inadequate orthognathic surgical correction.
Postoperative frontal ...
Development of
face
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2 organizing centers-
 Forebrain (prosencephalic) centre
 Hindbrain (rhombencephalic) centre
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 5 facial primordia
 Neural crest: source for almost all connective tissues in the face
DEVELOPMENT OF FACE
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Boundaries of stomodeum.
 Paired maxillary prominences- lateral
boundary
 Paired mandibular prominences- caudal
boundary...
 Facial prominences-active centers of growth – 4th to 8th week
 Connective tissue continuous from one prominence to anot...
 Lower jaw and lower lip are the first parts
of the face to form.
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 Nasal placodes & nasal pits- by the end of fourth week
 Primodia of the nose and and nasal cavities.
DEVELOPMENT OF FAC...
Nasal prominences , nasal pits
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Maxillary prominences grow- pushing nasal prominences
medially
Nasolacrimal groove
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MNP
MP
LNP
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•Auricular hillocks- seen by the
end of fifth week.
•Neck region
•Primordia for external acoustic
meatus and auricle.
www....
•By the end of sixth week
•Maxillary prominence merges
with lateral nasal prominence
•Continuity between side of
nose and ...
NASOLACRIMAL DUCT
Rod like ectodermal thickening in the floor of
Nasolacrimal groove.
Later as a result of cell degenerati...
 Medial nasal prominences merge with each other and with
fused lateral nasal & maxillary prominences
 Intermaxillary seg...
Intermaxillary segment gives
rise to
 Philtrum of the upper lip.
 Premaxillary part of the maxilla and its
associated gi...
MNPLNP
MP
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1. Frontonasal prominence: forehead, dorsum & apex of nose
2. Lateral nasal prominence: alae of nose
3. Medial nasal promi...
DEVELOPMENT OF PRIMARY
PALATE
 Palatal development spans week 5-12 , but weeks 6-9 are most
critical
 Formation of inter...
 Primary palate begins to develop from
deep part of the intermaxillary segment of
maxilla.
 Initially this segment is a ...
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DEVELOPMENT OF SECONDARY
PALATE
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Sixth week
Secondary palate develops from two
mesenchymal projections that extend from
internal aspects of the maxillary
p...
 As jaw develops tongue moves
inferiorly palatal shelves ascend to
a horizontal position and fuse in the
median plane.
 ...
 NASAL SEPTUM develops as a
downgrowth from internal aspects of
merged medial nasal prominences.
 Fusion between nasal s...
 Bone develops in the primary palate,
forming Premaxillary part of the maxilla.
 Gradually bone extends into the lateral...
Nasal septum
Bone development
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Theories for palatal shelf elevation
 Causes extrinsic to palatal shelves
1. Descent of the tongue due to pronounced sagi...
Intrinsic causes –
1. Hydration and polymerization of intercellular substances
producing an elastic elevating force (Walk...
 Most accepted theory-
elevation of the palatal shelves to horizontal
position is believed to be caused by an intrinsic s...
CLEFT LIP & PALATE
 Cleft lip and cleft palate are related embryologically but
are distinct entities
 Cleft lip: 1 in 75...
Genetics
 Non-syndromic inheritance is multifactorial
 Cleft Lip, With or Without Cleft Palate:
• One Parent-2%
• One Si...
Genetics
 Increased clefts with chromosome aberrations
 Clefts a part of a Syndrome 15-60% of time
 More than 200 syndr...
Epidemiology
 Cleft Lip +/- Palate- 2 Male: 1 Female
 Cleft Palate - 2 Female: 1 Male
(palatine processes fuse one week ...
Unilateral Cleft Lip
• Forms as a persistent labial groove
• Labial groove should disappear as the maxillary prom. fuse wi...
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 Nasal floor communicates with oral cavity
 Maxilla on cleft side is hypoplastic
 Columella is displaced to normal side...
Bilateral Cleft Lip
• Similar to unilateral cleft lip
• Central soft-tissue mass that moves freely
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 Clefting of alveolar process of maxilla as well as lip
 Complete cleft extends to incisive foramen
 Complete bilateral...
Posterior Cleft Anomalies
 Clefts extending through both soft and hard palate to the
incisive fossa
 Isolates anterior a...
Complete Cleft Palate
 Complete bilateral cleft
of the lip and alveolar
process of the maxillae
with complete bilateral
c...
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Development of tongue
Development begins
around the end of
fourth week in relation
to pharyngeal arches
in the floor of mo...
 Swellings from the first pharyngeal arch
Median tongue bud 2 distal buds
(tuberculum impar)
anterior two thirds of
epith...
 Two swellings caudal to foramen cecum
COPULA HYPOBRACHIAL
EMINENCE
Ventromedial parts ventromedial parts
of 2nd arch of ...
1st Brachial Arch
2nd Brachial Arch
3rd Brachial Arch
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Copula overgrown by
hypopharyngeal
eminence
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1st Brachial Arch
2nd Brachial Arch
3rd Brachial Arch
4th Brachial Arch
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Terminal sulcus-line
of fusion of the
anterior and
posterior parts of
the tongue.
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Nerve supply of tongue
 Anterior two-thirds
 lingual branch of chorda tympani
mandibular div of tri- branch of facial.n ...
Posterior third
glossopharyngeal.n superior laryngeal
branch of vagus.n
MUSCLES – all muscles of tounge are
supplied by hy...
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•Aglossia.
In this condition, a portion or all of the tongue
is absent. Rarely is all the tongue absent.
Microglossia
Mig...
 Macroglossia
 A congenital macroglossia is generally
caused by an overdevelopment of the
muscular portion of the tongue...
Ankyloglossia :
In this condition, the tongue is restricted in its movements by a
strand of mucosa - lingual frenum that ...
Congenital Lingual Cysts and Fistulas
Remnants of thyroglossal duct
Dysphagia
Fistulas open through foramen caecum
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SKULL
NEUROCRANIUM VISCEROCRANIUM
( clavaria & base of skull ) ( skeleton of face and associat
ed structures )
•Membranous...
Cartilagenous neurocranium
Development of neurocranium
Neural crest
cells
Paraxial
mesoderm
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 Ossification pattern-
• Occipital bone
• Body of sphenoid
• Ethmoid bone
 Other structures-
• Vomer bone of nasal septu...
Membranous neurocranium
Origin of mesenchyme
Neural crest
cells Paraxial
mesoderm
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Membranous neurocranium
Calvaria
•Frontal bone
•Parietal bone
•Squamous part of temporal bone
•Occipital bone
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Role of fontanelle
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VISCEROCRANIUM
CARTILAGINOUS VISCEROCRANIUM
•Middle ear ossicles
•Styloid process
•Hyoid bone
•Laryngeal cartilages
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MEMBRANOUS VISCEROCRANIUM
•Maxilla
•Zygomatic bone
•Squamous
temporal
•mandible
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Apert and Crouzon
Syndrome‟s
1906, Apert described a child with
acrocephalosyndactyly
1912, Crouzon described mother & d...
 Typical characteristics
 Craniosynostosis
• Coronal sutures fused at birth
• Larger than average head circumference at ...
Apert and
Crouzon
syndactyly
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 Facial features
 Shallow orbits with exophthalmos
 Retruded midface with relative prognathism
 Beaked nose
 Hypertel...
Development of mandible
 Intramembranous
 Meckle‟s cartilage – role
• Primitive structural support
• Morphogenic templat...
MECKLE’S
CARTILAGE
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DEVELOPING MANDIBLE MECKEL‟S CARTILAGE
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 Mandibular nerve – lingual branch
• inferior alveolar branch – mental
- incisive
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 Primary ossification center
 Anterior and posterior extension of growth
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 Height of bone is increasing at the same time as antero
– posterior growth.
 Mental nerve comes to lie in a shallow gro...
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 Developing tooth germs
 Formation of alveolar process – upward extension of
neural element
 Medial and lateral alveola...
Development of ramus
 Backward extension of neural
element behind and above mandibular
foramen
 Pre-osteoblast condensat...
By 10TH week the rudimentary mandible is formed almost
entirely by membranous ossification, with little direct involvemen...
 Secondary cartilages
Condylar cartilage
Coronoid cartilage
Symphyseal cartilage
 Distinguish from the primary Meckel's ...
CONDYLAR CARTILAGE
 10 week of IUL –first appears as a fringe
 Cone shaped structure
 14TH week of IUL – By endochondra...
CORONOID CARTILAGE
 About 16th week of IUL
 Strip along anterior border and tip of coronoid process
 Grows as response ...
SYMPHYSEAL CARTILAGE
 Two in number
 7 month of IUL in the mental region
 Fuses with mandible during the first year of ...
Development of nasomaxillary complex
 Maxilla – intramembranous
 Maxilla develops from the centre of ossification in the...
 No arch cartilage or PRIMARY CARTILAGE , but centre of
ossification is associated closely with the cartilage of the nasa...
SECONDARY CARTILAGE
 Zygomatic or malar cartilage appears in the developing
zygomatic process and for a short time adds
c...
COMMON FEATURE OF
DEVELOPMENT OF JAWS
 Both maxilla and mandible start developing from centres
of ossification in close r...
CLINICAL
CONSIDERATIONS
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Down Syndrome (Trisomy 21)
 1866, described by John
Landon Down
 Most common
 Prevalence 1 in 700 births
 Maternal age...
 Etiology: non-disjunction mutation
resulting in Trisomy 21
 Non-disjunction-error in cell division;
 Failure of chroma...
 Trisomy=3 chromosomes present instead of the
usual pair; associated with 3 main syndromes
 Trisomy 21 – Down syndrome
...
•Growth retardation
•Mental retardation
•Clinodactyly of 5th digit
(=incurving)
•Simian crease
(=single transverse palmar ...
Facial Characteristics
 Broad face
 Midface hypoplasia
 Flat occiput
 Flat nasal bridge
 Epicanthal folds
 Up-slanti...
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Prenatal growth & development /diploma orthodontic course by indian dental academy /certified fixed orthodontic courses by Indian dental academy

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Prenatal growth & development /diploma orthodontic course by indian dental academy /certified fixed orthodontic courses by Indian dental academy

  1. 1. PRE-NATAL GROWTH & DEVELOPMENT INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2.  What is EMBRYOLOGY? Embryology is the study of prenatal development of embryo and fetuses.  SIGNIFICANCE OF EMBRYOLOGY -Gives knowledge concerning beginning of human life and changes occurring during prenatal development. -Understanding normal post-natal growth -and development of various craniofacial abnormalities INTRODUCTION www.indiandentalacademy.com
  3. 3.  Period of ovum- fertilization to 2 weeks  Period of embryo – 2nd to 8th week  Period of fetus - 9th week to term Imp-week 4-8,teratogens www.indiandentalacademy.com
  4. 4. He who sees things grow from the beginning will have the finest view of them…….. -ARISTOTLE www.indiandentalacademy.com
  5. 5. Day 0 FERTILIZATION Human development begins at fertilization, the process during which a male sperm unites with a female oocyte to form a single zygote. Human development begins at fertilization, which occurs in the ampulla of the uterine tube www.indiandentalacademy.com
  6. 6. Zygote-contains chromosomes and genes that are derived from both mother and father. www.indiandentalacademy.com
  7. 7. THE FIRST WEEK  CLEAVAGE OF ZYGOTE: -Cleavage usually occurs as the zygote passes along the uterine tube. -Cleavage consist of repeated mitotic divisions of zygote. -The zygote divides into 2 cells, which then divides into 4,8 and so on. -The cells are called “BLASTOMERES‟‟. - 12 to 16 blastomeres, it is called as MORULA (fruit of mulberry tree). www.indiandentalacademy.com
  8. 8. Day 1-3  Cleavage  blastomeres  morula www.indiandentalacademy.com
  9. 9. 2 cell 4 cell 8 cell REF-THE DEVELOPING HUMAN, MOORE AND PERSAUDwww.indiandentalacademy.com
  10. 10. FORMATION OF BLASTOCYST  As morula enters uterus, a fluid-filled space called blastocyst cavity appears in morula.  As fluid increases, it separates blastomeres into two parts:- Outer cell layer, Trophoblast. -Inner cell mass, which act as primordium of embryo called Embryoblast Day 4-7 www.indiandentalacademy.com
  11. 11. Implantation  6 days after fertilization, blastocyst adheres to endometrial surface.  As soon as it attaches, the trophoblast starts proliferating rapidly and differentiates into 2 layers. -Cytotrophoblast (inner layer). -Syncytiotrophoblast (outer mass with finger-like processes). www.indiandentalacademy.com
  12. 12. Implantation www.indiandentalacademy.com
  13. 13.  Implantation of blastocyst commences at the end of 1st week and completed by end of 2nd week.  The syncytiotrophoblast release proteolytic enzymes which promotes proteolysis and invasion of maternal endometrium.. The Second week Completion of implantation: Day 8-14 www.indiandentalacademy.com
  14. 14. DAY 9  Isolated cavities called lacunae appear in syncytiotrophoblast  Adjacent lacunae fuse to form lacunar networks Capillaries around embryo become dilated to form - sinusoids www.indiandentalacademy.com
  15. 15.  Syncytiotrophoblast erodes sinusoids and maternal blood flows freely In lacunar networks  Communication with eroded endometrial capillaries  Primitive circulation between endometrium and placenta- uteroplacental circulation DAY 12 www.indiandentalacademy.com
  16. 16.  Site at which blastocyst EMBRYONIC POLE. gets implanted CLINICAL RELEVANCE Syncytiotrophoblast releases HUMAN CHORIONIC GONADOTROPHIN ( HCG ) HORMONE… which gives a positive pregnancy test at the end of the second week. www.indiandentalacademy.com
  17. 17. FORMATION OF AMNIOTIC CAVITY, EMBRYONIC DISC AND YOLK SAC:  As implantation of blastocyst progresses, a small cavity appears in the inner cell mass called “AMNIOTIC CAVITY”.  The blastocyst cavity / Exocoelomic cavity soon modifies to form “PRIMARY YOLK-SAC”. www.indiandentalacademy.com
  18. 18.  So now there are 2 cavities: 1. “AMNIOTIC CAVITY” (above) 2. “PRIMARY YOLK-SAC” (below - later forms secondary yolk sac) Soon the inner cell mass form 2 types of cells which lie Between these 2 cavities Epiblast: High columnar cells related to amniotic cavity. Hypoblast – squamous or cuboidal cell mass adjacent to primary yolk sac The epiblast and hypoblast together forms the “BILAMINAR EMBRYONIC DISC”. Second weekBILAMINAR DISC STAGE www.indiandentalacademy.com
  19. 19.  Defect in endometrium persists for 2 days- filled by a closing plug- fibrinous coagulum of blood.  In extra-embryonic mesoderm fluid filled spaces appear which fuse to form Extraembryonic Coelom www.indiandentalacademy.com
  20. 20. DAY 14 2 processes occur simultaneously: Formation of extraembryonic somatic and splanchnic mesoderm due to split of extraembryonic mesoderm by extraembryonic coelom. Extraembryonic coelom is now called chorionic cavity. www.indiandentalacademy.com
  21. 21.  Defect in endometrium disappears  Cells from hypoblast migrate along inside of Primary yolk sac – pinched off and smaller secondary yolk sac forms  Proliferation of cytotrophoblastic cells into syncytiotrophoblast leads to Formation of primary chorionic villi (later forms placenta). DAY 13 www.indiandentalacademy.com
  22. 22. DAY 14 The amniotic cavity (epiblast at floor) and secondary yolk sac (hypoblast at roof) resembles 2 balloons pressed together inside larger balloon (chorionic sac) suspended by connecting stalk - umbilical cord www.indiandentalacademy.com
  23. 23. DAY 14 Epiblastic cells- formation of primitive streak Hypoblastic cells in a localized area are now columnar and form a thickened circular area called pre-chordal plate which indicates the future site of the mouth and is an important organizer of the head region www.indiandentalacademy.com
  24. 24. THE THIRD WEEK  GASTRULATION : is a formative process by which the 3 germ layers & axial orientation are established in the embryo -Primitive streak. -Germ layers. -Formation of notochord  NEURULATION.  NEURAL CREST FORMATION. www.indiandentalacademy.com
  25. 25.  GASTRULATION:  the Bilaminar embryonic disc is converted to a Trilaminar embryonic disc.  It is the beginning of morphogenesis (development of body form).  It begins with formation of primitive streak at the surface of the embryonic disk. Third week www.indiandentalacademy.com
  26. 26. PRIMITIVE STREAK:  It results from proliferation and migration of the cells of epiblast to the median plane of the embryonic disc.  The primitive streak elongates by addition of cells to its caudal end  its cranial end proliferates to form primitive node. DAY 15,16 www.indiandentalacademy.com
  27. 27. As soon as the primitive streak appear, it is possible to identify the embryo‟s Cranio -caudal axis Primitive groove develops in the primitive streak that is continuous with a small depression in the primitive node, the primitive pit. www.indiandentalacademy.com
  28. 28. FATE OF PRIMITIVE STREAK  Normally the primitive streak undergoes disappears by the end of fourth week.  Remnants of primitive streak may persist and give rise to a large tumor – SACROCOCCYGEAL TERATOMA.  Need to be surgically excised . www.indiandentalacademy.com
  29. 29. Fetal Alcohol Syndrome  clinically described 30 years ago (1973), caused by maternal alcohol consumption during pregnancy.  Alcohol crosses the placenta from maternal circulation into fetal circulation  consists of a variable degree of birth defects and mental retardation, initially identified by a reduced head size and distinctive facial features  This Syndrome is 100% preventable. FAS www.indiandentalacademy.com
  30. 30. Fetal Alcohol SyndromeFAS •Maternal alcoholism causes effects of 2 types •In moderation i.e. 1-2 ounces/day (30ml) can cause fetal alcohol effects (FAE) -behavioral & learning defects •Chronic consumption leads to FAS. •Moderate &chronic consumption in the 1st trimester causes these effects. However development of brain spans the entire period of gestation, hence total abstinence from alcohol is advised www.indiandentalacademy.com
  31. 31. FAS CHARACTERISTICS: Microcephaly - leads to small head circumference Palpebral fissure - short opening of eye Epicanthal folds - fold of skin at inside of corner of eye Midface - flat Nasal Bridge - low Philtrum - Indistinct, Upper Lip - thin Micrognathia - small jaw Ears –the curve at top part of outer ear is underdeveloped and folded over parallel to curve beneath. Gives the appearance of a "railroad track" www.indiandentalacademy.com
  32. 32.  MANAGEMENT:  early intervention is critical to determine prognosis for a child with FAS  earlier provision of medical, clinical and educational intervention- better outcome  special needs pre-school programme  constant follow up www.indiandentalacademy.com
  33. 33.  FORMATION OF GERM LAYERS:  Soon after primitive streak appears, cells leave its deep surface and migrate to form a loose network of embryonic connective tissue called Mesenchyme  The mesenchyme forms the supporting tissue of the embryo. Third week www.indiandentalacademy.com
  34. 34.  the mesenchyme forms a layer called Intraembryonic mesoderm.  Some cells of the Epiblast displace the Hypoblast forming intraembryonic or embryonic endoderm in the roof of Yolk sac.  Cells remaining in the epiblast forms the Intraembryonic or Embryonic ectoderm in the floor of the amnion. Third week www.indiandentalacademy.com
  35. 35.  All the above cells have the potential to proliferate and differentiate into diverse types of cells, such as fibroblast, chondroblast and osteoblast.  In short the cells of the epiblast, through the process of gastrulation, give rise to all 3 germ layers in the embryo. Third week www.indiandentalacademy.com
  36. 36. DERIVATIVES OF GERM LAYERS  ECTODERM: Epidermis, hair, nail. Central and peripheral nervous system. Mammary, pituitary and subcutaneous gland. Enamel of teeth.  MESODERM :Connective tissue, cartilage, bone. Striated and smooth muscle. Heart, blood and lymphatic vessels. kidneys, ovaries, testes, spleen, cortex of adrenal gland.  ENDODERM: Epithelial lining of gastrointestinal and respiratory tracts, urinary bladder and urethra. Epithelial lining of tympanic cavity, tympanic antrum, auditory tube. www.indiandentalacademy.com
  37. 37. www.indiandentalacademy.com
  38. 38. FORMATION OF NOTOCHORD  Some mesenchymal cells migrate cranially from the primitive node and pit, forming a median cellular chord, the notochordal process.  The process soon acquires a lumen, the notochordal canal and grows cranially until it reaches the prechordal plate. DAY 18 www.indiandentalacademy.com
  39. 39.  The notochordal process cannot extent beyond the prechordal plate.  Place of fusion of upper ectoderm and lower endoderm, which will form the OROPHARYNGEAL MEMBRANE.  Various cellular events take place in the notochordal process which give rise to the NOTOCHORD. www.indiandentalacademy.com
  40. 40. prochordal plate Notochordal canal cloacal membrane www.indiandentalacademy.com
  41. 41. IMPORTANCE OF NOTOCHORD:  Defines primordial axis of embryo and gives rigidity.  Serves as basis for development of axial skeleton (bones of head and vertebral column).  Indicates future site of vertebral bodies. www.indiandentalacademy.com
  42. 42. NEURULATION  Formation of neural plate and neural folds and closure of these folds to form the neural tube constitute Neurulation. Neural plate and Neural tube:  As the notochord develops, the embryonic ectoderm over it thickens to form an elongated, slipper-like plate of thickened epithelial cells, the “neural plate” . DAY 19,20 www.indiandentalacademy.com
  43. 43.  Neural plate formation is induced by developing notochord.  The ectoderm of neural plate called Neuroectoderm gives rise to the “CENTRAL NERVOUS SYSTEM” i.e. the Brain and spinal chord www.indiandentalacademy.com
  44. 44. NEURULATION  At about 18th day, the neural plate invaginates along its central axis to form median “Neural groove”, which has neural folds on each side. www.indiandentalacademy.com
  45. 45.  The neural fold are the first signs of brain development.  By the end of 3rd week the neural folds begin to move together and fuse, converting neural plate into a “neural tube” NEURULATION www.indiandentalacademy.com
  46. 46. NEURAL CREST FORMATION  As the neural folds fuse to form the neural tube, some neuroectodermal cells lying along the crest of each neural fold lose their epithelial affinities and attachments to neighboring cells. www.indiandentalacademy.com
  47. 47.  Soon it forms a flattened irregular mass, the neural crest, between the neural tube and the overlying surface ectoderm.  Neural crest soon separates into right and left parts that migrates to the dorsolateral aspects of the neural tube and give rise to the sensory ganglia of the spinal and cranial nerves. www.indiandentalacademy.com
  48. 48.  CREST CELLS DERIVATIVES.  Neurolemmal sheath of peripherl nerves.  Meningeal coverings of the brain and the spinal cord.  Formation of pigment cells.  Several skeletal and muscular components in the head www.indiandentalacademy.com
  49. 49.  NEURAL TUBE DEFECTS- primarily results from failure of neural folds to fuse and form the neural tube in the brain region.  e.g.- ANENCEPHALY- anterior brain structures are lost and replaced by soft spongy mass. www.indiandentalacademy.com
  50. 50. Development of somites  As the notochord and neural tube form,intraembryonic mesoderm on each side proliferates to form a column of PARAXIAL MESODERM.  INTERMEDIATE MESODERM  LATERAL MESODERM www.indiandentalacademy.com
  51. 51. Development of somites DAYS 20-30 •Paraxial mesoderm differentiates into paired cuboidal bodies- somites •First appear in occipital region •42-44 pairs of Surface elevations by 5th week •Develop craniocaudally •Form axial skeleton www.indiandentalacademy.com
  52. 52. 4th week onwards... www.indiandentalacademy.com
  53. 53.  Paraxial mesoderm.  Lateral plate mesoderm.  Neural crest cells .  Ectodermal placodes Mesenchyme for formation of head region is derived from: www.indiandentalacademy.com
  54. 54. PHARYNGEAL APARATUS  “Branchial”- branchia, gill resemblance to fish embryo  - Pharyngeal arches (mesoderm)  - Pharyngeal clefts (ectoderm)  - Pharyngeal pouches (endoderm)  - Pharyngeal membranes clefts separate arches externally. Pouches separate arches internally. www.indiandentalacademy.com
  55. 55. PHARYNGEAL ARCHES  Pharyngeal arches consist of core of mesenchymal tissue covered on the outside by surface ectoderm and on inside by endoderm.  Apart from this, the arches also have migrated neural crest cells, which contribute to skeletal components of the face. www.indiandentalacademy.com
  56. 56.  By the end of the 4th week , 4 pairs of pharyngeal arches are visible externally as rounded ridges on each side of the future head and neck regions.  5tharch-often absent. If present the 5th and 6th arches are rudimentary & not visible on the surface.  Neural crest cells, in addition to forming nerve tissue, produce the bones of the cranium.  Within the pharyngeal arches, neural crest cells and lateral plate mesoderm give rise to bones of the jaw and lower face, the viscerocranium www.indiandentalacademy.com
  57. 57. Each arch is characterized by its own  Cartilaginous rod that forms the skeleton of the arch  muscular component  nerve component and  arterial component. www.indiandentalacademy.com
  58. 58. DERIVATIVES OF PHARYNGEAL Apparatus www.indiandentalacademy.com
  59. 59. SKELETAL DERIVATIVES www.indiandentalacademy.com
  60. 60. MUSCLE DERIVATIVES www.indiandentalacademy.com
  61. 61. NERVE SUPPLY www.indiandentalacademy.com
  62. 62. ARTERIAL SUPPLY www.indiandentalacademy.com
  63. 63.  The first pharyngeal arch is often called the mandibular arch.  First arch splits giving rise to 2 regions: - cranial part called Maxillary Process - Caudal part called Mandibular Process  MAXILLARY PROCESS gives rise to Maxilla  MANDIBULAR PROCESS gives rise to Mandible FIRST PHARYNGEAL ARCH www.indiandentalacademy.com
  64. 64. MAXILLARY PROCESS: mesenchyme of the maxillary process gives rise to  premaxilla,  maxilla,  zygomatic bone and  part of temporal bone through membranous ossification. FIRST PHARYNGEAL ARCH www.indiandentalacademy.com
  65. 65. MANDIBULAR PROCESS: Cartilage of the 1st arch is meckel‟s cartilage. Dorsal end-ossifies to form malleus and incus Middle part regresses, but perichondrium forms sphenomandibular ligament FIRST PHARYNGEAL ARCH www.indiandentalacademy.com
  66. 66. Meckle‟s cartilage  Ventral part-forms horse shoe shaped structure in the shape of future mandible and has close positional relationship to developing mandible but makes no contribution to it.  Mesenchymal tissue lateral to cartilage undergoes intramembranous ossification to form mandible and meckel‟s cartilage disappears www.indiandentalacademy.com
  67. 67.  MUSCULATURE:  Temporalis  Masseter  Pterygoids  Anterior belly of digastric  Mylohyoid  Tensor tympani  Tensor palatini. FIRST PHARYNGEAL ARCH www.indiandentalacademy.com
  68. 68. NERVE SUPPLY:  Nerve supply to muscles of the 1st arch is by mandibular branch of trigeminal nerve.  Sensory supply to the skin of face by ophthalmic, maxillary, an d mandibular branches of trigeminal nerve. FIRST PHARYNGEAL ARCH www.indiandentalacademy.com
  69. 69.  Called the hyoid arch as part of the hyoid bone develops here  The cartilage of 2nd arch is called as Reichert‟s cartilage. SECOND PHARYNGEAL ARCH www.indiandentalacademy.com
  70. 70.  It gives rise to,  Stapes  Styloid process of temporal bone  Stylohyoid ligament  Lesser horn and upper part of body of hyoid bone. SECOND PHARYNGEAL ARCH www.indiandentalacademy.com
  71. 71. MUSCLES:  Stepedius.  Posterior belly of digastric.  Auricular.  Muscles of facial expression SECOND PHARYNGEAL ARCH www.indiandentalacademy.com
  72. 72. NERVE:  Facial nerve supplies all these muscles. SECOND PHARYNGEAL ARCH www.indiandentalacademy.com
  73. 73. CARTILAGE of 3rd pharyngeal arch produces,  Lower part of body of hyoid bone.  Greater horn of hyoid bone. THIRD PHARYNGEAL ARCH www.indiandentalacademy.com
  74. 74. MUSCLE:  Stylopharyngeus muscle. NERVE:  Glossopharyngeal nerve. THIRD PHARYNGEAL ARCH www.indiandentalacademy.com
  75. 75. CARTILAGINOUS component of 4th and 6th pharyngeal arches fuse to form,  Thyroid cartilage.  Cricoid cartilage.  Arytenoid cartilage.  Corniculate cartilage.  Cuneiform cartilage. FOURTH AND SIXTH PHARYNGEAL ARCHES www.indiandentalacademy.com
  76. 76. MUSCLES: 4th arch:  cricothyroid,  levator palatini,  constrictors of pharynx , 6th arch:  intrinsic muscles of larynx. FOURTH AND SIXTH PHARYNGEAL ARCHES www.indiandentalacademy.com
  77. 77. NERVE:  4TH arch: Superior laryngeal branch of vagus nerve.  6th arch: Recurrent laryngeal branch of vagus nerve. FOURTH AND SIXTH PHARYNGEAL ARCHES www.indiandentalacademy.com
  78. 78. ARTERIAL SUPPLY  Pharyngeal arch arteries are called aortic arches  from arch 1 & 2-arteries significantly smaller  Arch 1- part of maxillary artery  Arch 2- hyoid & stapedial arteries  Arch 3- part of carotid system  Arch 4- left side-arch of aorta Right side-subclavian artery  Arch 6- pulmonary arteries www.indiandentalacademy.com
  79. 79.  Human embryo has 5 pairs of pharyngeal pouches, the last one is atypical and often considered as part of the 4th pouch.  Composed of Endoderm PHARYNGEAL POUCHES www.indiandentalacademy.com
  80. 80.  It comes in contact with the epithelial lining of the 1st pharyngeal cleft, which is a future external auditory meatus.  The distal portion widens into sac-like structure forming primitive tympanic cavity, the proximal part remains narrow, forming Auditory (Eustachian) tube.  lining of the tympanic cavity- forms tympanic membrane or eardrum. FIRST PHARYNGEAL POUCH 1st pouch forms stalk-like diverticulum- Tubotympanic recess. www.indiandentalacademy.com
  81. 81.  Buds are secondarily invaded by mesodermal tissue thus forming primordium of palatine tonsil  3rd and 5th month- tonsil is infiltrated by lymphatic tissue.  Part of pouch remains and forms tonsillar fossa in adult. second PHARYNGEAL POUCH The epithelial lining of 2nd pouch proliferates and form Buds that penetrate into surrounding mesenchyme. www.indiandentalacademy.com
  82. 82. 3rd and 4th pouches are characterized by ,  DORSAL WING and VENTRAL WING In 5th week, from 3rd pouch  Dorsal wing- Inferior parathyroid gland.  Ventral wing- Thymus gland. THIRD PHARYNGEAL POUCH www.indiandentalacademy.com
  83. 83. Both gland primordia lose their connection with pharyngeal wall, the thymus then migrates in a caudal and medial direction, pulling the Inferior parathyroid gland with it. www.indiandentalacademy.com
  84. 84.  The primordia finally rest on the dorsal surface of the thyroid gland and forms inferior parathyroid gland.  The thymus gland moves rapidly to its final position in the thorax, fuses with counterpart from opposite side. THIRD PHARYNGEAL POUCH www.indiandentalacademy.com
  85. 85.  Of the 4th pouch Dorsal wing- superior parathyroid gland.  It also loses contact with wall of pharynx and migrate caudally and medially and finally is located on the dorsal surface of thyroid. FOURTH PHARYNGEAL POUCH www.indiandentalacademy.com
  86. 86.  Last pharyngeal pouch to develop  Usually considered to be a part of 4th pouch.  Gives rise to – Ultimobranchial body, which gets incorporated into thyroid gland giving rise to parafollicular or „c‟ cells of thyroid gland which secrete calcitonin, hormone involved in regulation of calcium level in blood. FIFTH PHARYNGEAL POUCH www.indiandentalacademy.com
  87. 87. Derivatives PHARYNGEAL POUCHES www.indiandentalacademy.com
  88. 88.  located between arches externally  these are spaces, thus contain no germ layer components  Four pharyngeal clefts, of which only 1st contributes to the definitive structure - external auditory meatus. DERIVATIVES OF PHARYNGEAL CLEFTS/grooves www.indiandentalacademy.com
  89. 89.  Active proliferation of mesenchymal tissue of 2nd arch, results in overlapping of it over 3rd and 4th arch causing the 2nd , 3rd and 4th clefts lose contact with the outside and forms a cervical sinus which eventually obliterates as neck develops. DERIVATIVES OF PHARYNGEAL CLEFTS www.indiandentalacademy.com
  90. 90. Pharyngeal Membranes:  Appear in the floors of the pharyngeal grooves and form where the epithelia of the groove & pouches approach each other  as most clefts are filled in, only first membrane develops.  this lies close to external auditory meatus and develops into the Tympanic membrane www.indiandentalacademy.com
  91. 91.  Primordial mouth or stomodeum appears as slight depression of surface ectoderm  It is separated from cavity of primordial pharynx by oropharyngeal membrane  Bilaminar-ectoderm and endoderm STOMODEUM www.indiandentalacademy.com
  92. 92. •Ruptures at 26 days •Communication of primordial cavity and foregut with amniotic cavity www.indiandentalacademy.com
  93. 93. CLINICAL COMMENT Most congenital anomalies in head- neck region originate during transformation of the pharyngeal apparatus into its adult derivatives. Thus the term “branchial anomalies” results from persistence of parts that normally disappear as adult structures develop. www.indiandentalacademy.com
  94. 94.  BRANCHIAL FISTULAS:  -an abnormal canal that opens internally into tonsillar sinus and externally in the side of the neck.  persistence of parts of the 2nd pharyngeal groove and pouch.  Fistula ascends from its opening in the neck through the subcutaneous tissue and platysma muscle to reach the carotid sheath – passes between the internal & external carotid arteries and opens into the tonsillar sinus CLINICAL CORRELATION www.indiandentalacademy.com
  95. 95. BRANCHIAL CYST:  Remnants of parts of cervical sinus and/or the 2nd pharyngeal groove may persist and form a spherical or elongated cyst.  They may be associated with branchial sinuses and drain through them,  these cysts often lie free in the neck just inferior to the angle of the mandible www.indiandentalacademy.com
  96. 96.  May develop anywhere along the anterior border of SCM muscle  Slowly enlarging painless swelling in the neck. www.indiandentalacademy.com
  97. 97.  NEURAL CREST CELLS: Essential for formation of craniofacial region but disruption results in severe craniofacial malformation :  1ST ARCH SYNDROME- Treacher collins syndrome (mandibulofacial dysostosis) Pierre-Robin sequence  Digeorge sequence (3rd and 4th pharyngeal pouch syndrome).  Goldenhar syndrome (Hemifacial microsomia ). CLINICAL CORRELATION www.indiandentalacademy.com
  98. 98. TCS  First described by Thomson and Toynbee in 1846-47 Later, essential components described by Treacher Collins in 1960  Autosomal dominant inheritance  Associated with increased paternal age  Prevalence of 1 in 50,000 Treacher collins syndrome (mandibulofacial dysostosis) www.indiandentalacademy.com
  99. 99. Characteristics:  Fishlike” facial appearance  Usually bilateral and symmetric expression  Degree of malformation at birth is stable and non-progressive  Dolichofacial pattern  Hypoplastic supraorbital rims and underdeveloped zygomatic bones resulting in malar hypoplasia. TCS www.indiandentalacademy.com
  100. 100. TCS  “Cleft palate in 35%  Downward slanting palpebral fissures  Retrusive mandible and maxilla  High mandibular plane angle– Anterior open bite  Antegonial notching  Malformed external ear  Normal intelligence www.indiandentalacademy.com
  101. 101. Treacher Collins syndrome 1. Preoperative frontal view of 16-year-old patient with Treacher Collins Syndrome. No previous correction had been performed. 2. Postoperative frontal view 1 year after orthognathic surgery. 3. Pre and postoperative lateral views of same patient. 1. 2. 3. www.indiandentalacademy.com
  102. 102. PRS  Triad of micrognathia, glossoptosis and cleft palate  First described by St. Hilaire in 1822  Pierre Robin first recognized the association of micrognathia and glossoptosis in 1923  Prevalence: 1 of every 8,500 newborns PIERRE ROBIN SEQUENCE Alters 1st arch structures, with mandible most severely affected. www.indiandentalacademy.com
  103. 103.  The initiating defect is micrognathia which results in posterior displacement of the tongue i.e. glossoptosis and obstruction to full closure of palatine processes resulting in bilateral cleft palate PRS www.indiandentalacademy.com
  104. 104.  Occurs because the 3rd and 4th pharyngeal pouches fail to differentiate into thymus and parathyroid glands.  Congenital thymic aplasia and absence of parathyroid glands with or without cardiovascular defects. DIGEORGE SEQUENCE: www.indiandentalacademy.com
  105. 105. characteristics  Congenital hypo-parathyroidism  Increased susceptibility to infections  Shortened philtrum of lip  Low set notched ears  Nasal clefts  micrognathia,  And cardiac abnormalities – defects of aortic arch & heart www.indiandentalacademy.com
  106. 106. Characteristics  Maxilla, temporal,& zygomatic bones are reduced in size and flattened.  Facial asymmetry  Ear, eye, and vertebral defects are common. i.e. Occuloauriculovertebral disease  Epibulbar Dermoids which are benign tumors located just inside the opening of the eye or the eyeballs, cause problems with vision. HEMIFACIAL MICROSOMIA/GOLDENHAR SYNDROME: www.indiandentalacademy.com
  107. 107. Preoperative frontal view of 17-year-old patient after inadequate orthognathic surgical correction. Postoperative frontal view after distraction osteogenesis and dermal fat graft to left cheek. Preoperative left oblique view shows deformity and after reconstruction GS www.indiandentalacademy.com
  108. 108. Development of face www.indiandentalacademy.com
  109. 109. 2 organizing centers-  Forebrain (prosencephalic) centre  Hindbrain (rhombencephalic) centre www.indiandentalacademy.com
  110. 110.  5 facial primordia  Neural crest: source for almost all connective tissues in the face DEVELOPMENT OF FACE www.indiandentalacademy.com
  111. 111. Boundaries of stomodeum.  Paired maxillary prominences- lateral boundary  Paired mandibular prominences- caudal boundary  Nasal part of FNP- rostral boundary www.indiandentalacademy.com
  112. 112.  Facial prominences-active centers of growth – 4th to 8th week  Connective tissue continuous from one prominence to another. DEVELOPMENT OF FACE www.indiandentalacademy.com
  113. 113.  Lower jaw and lower lip are the first parts of the face to form. www.indiandentalacademy.com
  114. 114.  Nasal placodes & nasal pits- by the end of fourth week  Primodia of the nose and and nasal cavities. DEVELOPMENT OF FACE www.indiandentalacademy.com
  115. 115. Nasal prominences , nasal pits www.indiandentalacademy.com
  116. 116. Maxillary prominences grow- pushing nasal prominences medially Nasolacrimal groove www.indiandentalacademy.com
  117. 117. MNP MP LNP www.indiandentalacademy.com
  118. 118. •Auricular hillocks- seen by the end of fifth week. •Neck region •Primordia for external acoustic meatus and auricle. www.indiandentalacademy.com
  119. 119. •By the end of sixth week •Maxillary prominence merges with lateral nasal prominence •Continuity between side of nose and cheek region •Nasolacrimal duct NLG www.indiandentalacademy.com
  120. 120. NASOLACRIMAL DUCT Rod like ectodermal thickening in the floor of Nasolacrimal groove. Later as a result of cell degeneration cord canalizes into Nasolacrimal duct. Part of duct which fails to canalize – ATRESIA OF NASOLACRIMAL DUCT. www.indiandentalacademy.com
  121. 121.  Medial nasal prominences merge with each other and with fused lateral nasal & maxillary prominences  Intermaxillary segment www.indiandentalacademy.com
  122. 122. Intermaxillary segment gives rise to  Philtrum of the upper lip.  Premaxillary part of the maxilla and its associated gingiva.  The primary palate. www.indiandentalacademy.com
  123. 123. MNPLNP MP www.indiandentalacademy.com
  124. 124. 1. Frontonasal prominence: forehead, dorsum & apex of nose 2. Lateral nasal prominence: alae of nose 3. Medial nasal prominence: nasal septum, philtrum, premaxilla, primary palate 4. Maxillary prominence: upper cheek, most of maxilla and lip 5. Mandibular prominence: mandible, chin, lower lip, lower cheek Disruptions in the formation of these prominences leads to facial clefting and other defects. Summary of Facial Development www.indiandentalacademy.com
  125. 125. DEVELOPMENT OF PRIMARY PALATE  Palatal development spans week 5-12 , but weeks 6-9 are most critical  Formation of intermaxillary segment from merged medial nasal prominences www.indiandentalacademy.com
  126. 126.  Primary palate begins to develop from deep part of the intermaxillary segment of maxilla.  Initially this segment is a wedge shaped mass of mesenchyme between internal surface of maxillary prominence.  Primary palate forms the premaxillary part of the maxilla. www.indiandentalacademy.com
  127. 127. www.indiandentalacademy.com
  128. 128. DEVELOPMENT OF SECONDARY PALATE www.indiandentalacademy.com
  129. 129. Sixth week Secondary palate develops from two mesenchymal projections that extend from internal aspects of the maxillary prominences. ( lateral palatine processes ) project inferomedially. www.indiandentalacademy.com
  130. 130.  As jaw develops tongue moves inferiorly palatal shelves ascend to a horizontal position and fuse in the median plane.  Palatal shelves also fuse with the nasal septum and posterior part of primary palate. www.indiandentalacademy.com
  131. 131.  NASAL SEPTUM develops as a downgrowth from internal aspects of merged medial nasal prominences.  Fusion between nasal septum and palatine processes ninth to twelfth week. www.indiandentalacademy.com
  132. 132.  Bone develops in the primary palate, forming Premaxillary part of the maxilla.  Gradually bone extends into the lateral palatine processes to form HARD PALATE.  Posterior part do not ossify SOFT PALATE. www.indiandentalacademy.com
  133. 133. Nasal septum Bone development www.indiandentalacademy.com
  134. 134. Theories for palatal shelf elevation  Causes extrinsic to palatal shelves 1. Descent of the tongue due to pronounced sagittal growth spurt of the Meckle's cartilage and the mandible (Coleman 1965; Burdi & Silvey 1969) 2. Myoneural activity within the tongue causing descent (Wragg et al 1969) 3. shelves being pushed up by the tongue (Walker 1971) 4.mouth opening reflexes (Humphrey 1969) www.indiandentalacademy.com
  135. 135. Intrinsic causes – 1. Hydration and polymerization of intercellular substances producing an elastic elevating force (Walker 1961) 2. differential growth of one side of the palatal shelf (Wood & Kraus, 1962) 3. turgor produced by a build up of mucopolysaccharides , predominantly hyaluronic acid (Andersen et al 1967) 4. serotonin release from neural tissue (Zimmerman et al 1981) 5. degree of mesenchymal cell activity at different sites and stages of palatal development (Singh and Moxham 1993) Ref- fundamentals of craniofacial growth - Sperberwww.indiandentalacademy.com
  136. 136.  Most accepted theory- elevation of the palatal shelves to horizontal position is believed to be caused by an intrinsic shelf elevating force that is generated by the hydration of hyaluronic acid in the mesenchymal cells within the palatal process www.indiandentalacademy.com
  137. 137. CLEFT LIP & PALATE  Cleft lip and cleft palate are related embryologically but are distinct entities  Cleft lip: 1 in 750; Cleft palate: 1 in 2500  Effects on appearance, speech, feeding Associated Dental Abnormalities  Supernumerary Teeth- 20%  Dystrophic Teeth- 30%  Missing Teeth- 50%  Malocclusion- 100% www.indiandentalacademy.com
  138. 138. Genetics  Non-syndromic inheritance is multifactorial  Cleft Lip, With or Without Cleft Palate: • One Parent-2% • One Sibling- 4% Two Siblings- 9% • One Parent + One Sibling- 15%  Cleft Palate: • One Parent- 7% • One Sibling- 2% Two Siblings- 1% • One Parent + One Sibling- 17% www.indiandentalacademy.com
  139. 139. Genetics  Increased clefts with chromosome aberrations  Clefts a part of a Syndrome 15-60% of time  More than 200 syndromes include clefts  Cleft Palate- Apert‟s, Stickler‟s, Treacher  Cleft Lip +/- Palate- Van der Woude‟s, Waardenberg‟s www.indiandentalacademy.com
  140. 140. Epidemiology  Cleft Lip +/- Palate- 2 Male: 1 Female  Cleft Palate - 2 Female: 1 Male (palatine processes fuse one week later in females)  Cleft Lip +/- Palate- Native Americans > Oriental and Caucasians > Blacks  Cleft Palate- Same among ethnic groups  Environmental: Ethanol, Rubella virus, thalidomide, aminopterin, smoking  Increased Clefts with maternal diabetes mellitus and amniotic band syndrome  Increased Clefts with increased paternal age www.indiandentalacademy.com
  141. 141. Unilateral Cleft Lip • Forms as a persistent labial groove • Labial groove should disappear as the maxillary prom. fuse with merged medial nasal prominences • Stretching of epithelium causes tissue breakdown and cleft formation www.indiandentalacademy.com
  142. 142. www.indiandentalacademy.com
  143. 143.  Nasal floor communicates with oral cavity  Maxilla on cleft side is hypoplastic  Columella is displaced to normal side  Nasal ala on cleft side is laterally, posteriorly, and inferiorly displaced www.indiandentalacademy.com
  144. 144. Bilateral Cleft Lip • Similar to unilateral cleft lip • Central soft-tissue mass that moves freely www.indiandentalacademy.com
  145. 145.  Clefting of alveolar process of maxilla as well as lip  Complete cleft extends to incisive foramen  Complete bilateral anterior cleft isolates the anterior and posterior parts of the palate  Result from failure of lateral palatine processes to fuse to primary palate Anterior Cleft Anomalies www.indiandentalacademy.com
  146. 146. Posterior Cleft Anomalies  Clefts extending through both soft and hard palate to the incisive fossa  Isolates anterior and posterior parts of palate  Result from failure of lateral palatine processes to grow medially and fuse to each other www.indiandentalacademy.com
  147. 147. Complete Cleft Palate  Complete bilateral cleft of the lip and alveolar process of the maxillae with complete bilateral cleft of the anterior and posterior palate Complete bilateral cleft of the lip and alveolar process of the maxillae with bilateral cleft of the anterior palate and unilateral cleft of the posterior palate www.indiandentalacademy.com
  148. 148. www.indiandentalacademy.com
  149. 149. www.indiandentalacademy.com
  150. 150. www.indiandentalacademy.com
  151. 151. www.indiandentalacademy.com
  152. 152. www.indiandentalacademy.com
  153. 153. www.indiandentalacademy.com
  154. 154. www.indiandentalacademy.com
  155. 155. Development of tongue Development begins around the end of fourth week in relation to pharyngeal arches in the floor of mouth. www.indiandentalacademy.com
  156. 156.  Swellings from the first pharyngeal arch Median tongue bud 2 distal buds (tuberculum impar) anterior two thirds of epithelium proliferates tongue Downwards (thyroglossal duct) To form the thyroid gland. www.indiandentalacademy.com
  157. 157.  Two swellings caudal to foramen cecum COPULA HYPOBRACHIAL EMINENCE Ventromedial parts ventromedial parts of 2nd arch of 3rd and 4th arch Overgrown by hypo forms the posterior Brachialeminence two thirds of the tongue.www.indiandentalacademy.com
  158. 158. 1st Brachial Arch 2nd Brachial Arch 3rd Brachial Arch www.indiandentalacademy.com
  159. 159. Copula overgrown by hypopharyngeal eminence www.indiandentalacademy.com
  160. 160. 1st Brachial Arch 2nd Brachial Arch 3rd Brachial Arch 4th Brachial Arch www.indiandentalacademy.com
  161. 161. Terminal sulcus-line of fusion of the anterior and posterior parts of the tongue. www.indiandentalacademy.com
  162. 162. Nerve supply of tongue  Anterior two-thirds  lingual branch of chorda tympani mandibular div of tri- branch of facial.n ( taste geminal.n (sensory) buds except for vallate papillae ) www.indiandentalacademy.com
  163. 163. Posterior third glossopharyngeal.n superior laryngeal branch of vagus.n MUSCLES – all muscles of tounge are supplied by hypoglossal nerve except for palatoglossus which is supplied by pharyngeal plexus fibres from the vagus nerve. www.indiandentalacademy.com
  164. 164. www.indiandentalacademy.com
  165. 165. •Aglossia. In this condition, a portion or all of the tongue is absent. Rarely is all the tongue absent. Microglossia Migrognathia and limb defects (Hanhart‟s syndrome) APPLIED ASPECTS www.indiandentalacademy.com
  166. 166.  Macroglossia  A congenital macroglossia is generally caused by an overdevelopment of the muscular portion of the tongue.  Lymphangiomas may occur alone or (more frequently) in association with hemangiomas The tongue is the most common oral location for this lesion. Together with hemangioma, lymphangioma is an important cause of congenital macroglossia.  Macroglossia may develop after removal of teeth. This develops as a hypertrophy (increase in cell size) when the teeth no longer contain the tongue within the previously established boundaries. www.indiandentalacademy.com
  167. 167. Ankyloglossia : In this condition, the tongue is restricted in its movements by a strand of mucosa - lingual frenum that attaches the anterior third of the tongue to the floor of the mouth and the lingual gingival mucosa. Extends to the tip of tongue interfering with free protrusion Persons with this condition are commonly called "tongue-tied." Treatment is surgical. www.indiandentalacademy.com
  168. 168. Congenital Lingual Cysts and Fistulas Remnants of thyroglossal duct Dysphagia Fistulas open through foramen caecum www.indiandentalacademy.com
  169. 169. SKULL NEUROCRANIUM VISCEROCRANIUM ( clavaria & base of skull ) ( skeleton of face and associat ed structures ) •Membranous •cartilaginous www.indiandentalacademy.com
  170. 170. Cartilagenous neurocranium Development of neurocranium Neural crest cells Paraxial mesoderm www.indiandentalacademy.com
  171. 171.  Ossification pattern- • Occipital bone • Body of sphenoid • Ethmoid bone  Other structures- • Vomer bone of nasal septum • Petrous and mastoid part of temporal bone www.indiandentalacademy.com
  172. 172. Membranous neurocranium Origin of mesenchyme Neural crest cells Paraxial mesoderm www.indiandentalacademy.com
  173. 173. www.indiandentalacademy.com
  174. 174. Membranous neurocranium Calvaria •Frontal bone •Parietal bone •Squamous part of temporal bone •Occipital bone www.indiandentalacademy.com
  175. 175. Role of fontanelle www.indiandentalacademy.com
  176. 176. VISCEROCRANIUM CARTILAGINOUS VISCEROCRANIUM •Middle ear ossicles •Styloid process •Hyoid bone •Laryngeal cartilages www.indiandentalacademy.com
  177. 177. MEMBRANOUS VISCEROCRANIUM •Maxilla •Zygomatic bone •Squamous temporal •mandible www.indiandentalacademy.com
  178. 178. Apert and Crouzon Syndrome‟s 1906, Apert described a child with acrocephalosyndactyly 1912, Crouzon described mother & daughter with craniofacial dysostosis Both are autosomal dominant Incidence is ~ 15 to 16 per 1,000,000 births www.indiandentalacademy.com
  179. 179.  Typical characteristics  Craniosynostosis • Coronal sutures fused at birth • Larger than average head circumference at birth  Midfacial malformation and hypoplasia  Shallow orbits with exophthalmos  Apert Syndrome: symmetric syndactyly (=fusion of digits) of hands and feet Apert and Crouzon www.indiandentalacademy.com
  180. 180. Apert and Crouzon syndactyly www.indiandentalacademy.com
  181. 181.  Facial features  Shallow orbits with exophthalmos  Retruded midface with relative prognathism  Beaked nose  Hypertelorism  Downward slanting palpebral fissures Apert and Crouzon www.indiandentalacademy.com
  182. 182. Development of mandible  Intramembranous  Meckle‟s cartilage – role • Primitive structural support • Morphogenic template www.indiandentalacademy.com
  183. 183. MECKLE’S CARTILAGE www.indiandentalacademy.com
  184. 184. DEVELOPING MANDIBLE MECKEL‟S CARTILAGE www.indiandentalacademy.com
  185. 185.  Mandibular nerve – lingual branch • inferior alveolar branch – mental - incisive www.indiandentalacademy.com
  186. 186.  Primary ossification center  Anterior and posterior extension of growth www.indiandentalacademy.com
  187. 187.  Height of bone is increasing at the same time as antero – posterior growth.  Mental nerve comes to lie in a shallow groove & then a definite notch  Formation of trough composed of lateral and medial plates. Notch containing nerve converted into foramen.  Closure & formation of incisive canal – part of mandibular canal  Neural element www.indiandentalacademy.com
  188. 188. www.indiandentalacademy.com
  189. 189.  Developing tooth germs  Formation of alveolar process – upward extension of neural element  Medial and lateral alveolar plates - formation of secondary trough www.indiandentalacademy.com
  190. 190. Development of ramus  Backward extension of neural element behind and above mandibular foramen  Pre-osteoblast condensation  Coronoid and angular processes added for muscular attachment  Point of divergence is marked by – Lingula www.indiandentalacademy.com
  191. 191. By 10TH week the rudimentary mandible is formed almost entirely by membranous ossification, with little direct involvement of MECKEL‟S CARTILAGE www.indiandentalacademy.com
  192. 192.  Secondary cartilages Condylar cartilage Coronoid cartilage Symphyseal cartilage  Distinguish from the primary Meckel's cartilage:-  histologic structure (large haphazardly arranged chondrocytes & sparse intercellular matrix) www.indiandentalacademy.com
  193. 193. CONDYLAR CARTILAGE  10 week of IUL –first appears as a fringe  Cone shaped structure  14TH week of IUL – By endochondral ossification this mass of cartilage converted quickly to bone.  This cartilage persists until the end of the second decade of life, providing a mechanism for growth of the mandible. www.indiandentalacademy.com
  194. 194. CORONOID CARTILAGE  About 16th week of IUL  Strip along anterior border and tip of coronoid process  Grows as response to the developing temporalis muscle  Fuses with ramus & disappears before birth www.indiandentalacademy.com
  195. 195. SYMPHYSEAL CARTILAGE  Two in number  7 month of IUL in the mental region  Fuses with mandible during the first year of post-natal life www.indiandentalacademy.com
  196. 196. Development of nasomaxillary complex  Maxilla – intramembranous  Maxilla develops from the centre of ossification in the mesenchyme of the maxillary process of the first arch www.indiandentalacademy.com
  197. 197.  No arch cartilage or PRIMARY CARTILAGE , but centre of ossification is associated closely with the cartilage of the nasal capsule.  Centre of ossification-at division of infraorbital into anterosuperior dental nerve.  spread of ossification –  Upwards – frontal  Downwards – lateral alveolar plate  Inward – palatal process  Backward – zygomatic process  Forwards – pre-maxillary region  Medial alveolar plate along with Lateral alveolar plate trough around maxillary tooth germ MAXILLA www.indiandentalacademy.com
  198. 198. SECONDARY CARTILAGE  Zygomatic or malar cartilage appears in the developing zygomatic process and for a short time adds considerably to development of maxilla.  Body of maxilla is relatively small because the maxillary sinus is not developed.  Formation of sinus takes place in 16th week as a shallow groove on the nasal aspect of the developing maxilla.  At birth sinus is still the rudimentary structure about the www.indiandentalacademy.com
  199. 199. COMMON FEATURE OF DEVELOPMENT OF JAWS  Both maxilla and mandible start developing from centres of ossification in close relation to bifurcation of corresponding nerves  They form from 2 facial swellings which have the same origin  Each has a relation to a primary cartilaginous skeleton  Both form a neural element & alveolar element.  Finally, both develop SECONDARY CARTILAGE to assist in their growth. www.indiandentalacademy.com
  200. 200. CLINICAL CONSIDERATIONS www.indiandentalacademy.com
  201. 201. Down Syndrome (Trisomy 21)  1866, described by John Landon Down  Most common  Prevalence 1 in 700 births  Maternal age >35 carries increased risk www.indiandentalacademy.com
  202. 202.  Etiology: non-disjunction mutation resulting in Trisomy 21  Non-disjunction-error in cell division;  Failure of chromatids of a chromosome to disjoin during meiosis Down Syndrome www.indiandentalacademy.com
  203. 203.  Trisomy=3 chromosomes present instead of the usual pair; associated with 3 main syndromes  Trisomy 21 – Down syndrome  Trisomy 18 – Edwards syndrome  Trisomy 13 – Patau syndrome  Infants with trisomy 18 &13 are severely malformed and mentally retarded and usually die early in infancy Down Syndrome www.indiandentalacademy.com
  204. 204. •Growth retardation •Mental retardation •Clinodactyly of 5th digit (=incurving) •Simian crease (=single transverse palmar crease) •Congenital heart defects Characteristic features: Down Syndrome www.indiandentalacademy.com
  205. 205. Facial Characteristics  Broad face  Midface hypoplasia  Flat occiput  Flat nasal bridge  Epicanthal folds  Up-slanting palpebral fissures  Progressive enlargement of lips  Small ears Down Syndrome www.indiandentalacademy.com
  206. 206. THANK-YOU www.indiandentalacademy.com For more details please visit www.indiandentalacademy.com

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