Branchial pharyngeal arches_concise /certified fixed orthodontic courses by Indian dental academy

Head and Neck Embryology
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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Branchial and Pharyngeal Arches
 Fourth week
 Neural crest cells
– Most skeletal and connective tissue in H&N
 Numbered cranial  caudal
 Four well-defined pairs visible externally
 Fifth and sixth rudimentary
 Separated by grooves

 First = Mandibular
– Mandibular Prominence  jaw
– Maxillary Prominence  maxilla/zyg/temp
 Second = Hyoid

 Fate
– Typical arch contains
• Aortic arch
• Cartilaginous rod (skeleton of arch)
• Muscular component
• Nerve

Pharyngeal Pouches
 First
– Tubotympanic recess  tympanic membrane
– Connects with pharynx  eustachian tube
 Second
– Palatine tonsil, tonsillar fossa
 Third
– Inferior parathyroid gland
– Thymus

Pharyngeal Pouches
 Fourth
– Superior parathyroid gland
– Ultimobranchial body fuses with thyroid
– Parafollicular C cells  calcitonin
 Fifth
– Rudimentary

Pharyngeal Pouches

Branchial or Pharyngeal Grooves
 Four on each side
 Separate branchial or pharyngeal arches
 First  External acoustic meatus
 Others lie in depression (cervical sinus)
which obliterates

Branchial or Pharyngeal Grooves

Branchial or Pharyngeal
Membranes
 Only one pair contribute to adult structures
 First  tympanic membrane

Branchial and Pharyngeal
Anomalies
 Congenital Auricular
Sinuses and Cysts
– Small sinuses (pits)
and cysts commonly
found in a triangular
area of skin anterior to
the ear
– May be remnant of
branchial or
pharyngeal groove

Anomalies
 Branchial Sinuses
– Lateral cervical:
Uncommon, open
externally (neck), failure of
second groove or cervical
sinus to obliterate
– External branchial sinuses:
Mucous d/c from infant’s
neck, bilateral in 10%
– Internal branchial sinuses:
Rare, persistent second
pouch, open into
intratonsillar cleft

Anomalies
 Branchial Fistula
– Connection between
intratonsillar cleft and neck
– Runs between internal and
external carotids
– Persistent second groove and
second pouch

Anomalies
 Branchial Cysts
– Develop along anterior
border of
sternocleidomastoid
– Most inferior to angle
of mandible
– Often present in
adulthood
– Remnants of cervical
sinus and/or second
groove

Anomalies
 Branchial Vestiges
– Cartilaginous or bony
remnants
– Usually anterior to
inferior third of
sternocleidomastoid

Anomalies
 First Arch Syndrome
 First branchial or
pharyngeal arch
– Treacher Collins syndrome
• Malar hypoplasia, down-
slanting of palpebral
fissures, lower eyelid
colobomas, ear
deformations
– Pierre Robin syndrome
• Hypoplasia of the
mandible, cleft palate, and
defects of the eye and ear

Anomalies
 DiGeorge Syndrome (Congenital Thymic and
Parathyroid Aplasia)
– Failure of third and fourth pouches to differentiate into
thymus and parathyroid glands
– Hypoparathyroidism
– Increased incidence of infections
– Shortened philtrum
– Low-set notched ears
– Nasal clefts
– Thyroid hypoplasia
– Cardiac anomalies

Anomalies
 Accessory Thymic
Tissue
– Isolated portion of
thymic tissue may
persist
– Often in close
association with
inferior parathyroid
gland

Anomalies
 Ectopic Parathyroid
Gland
– Variable in number (2-
6) and location
– Superior more constant
than inferior
– Thyroid to thorax
 Absence of Parathroid
Gland

Thyroid Gland
 Begins as thickening in
the floor of the pharynx
 Forms an outpouching
(thyroid diverticulum)
 Descends into neck
passing ventral to hyoid
bone and laryngeal
cartilages
 Connected to tongue by
thryoglossal duct at
foramen cecum

Thyroid Gland
 Isthmus connects right
and left lobes
 Thyroglossal duct
degenerates
 Blind pit marks the
foramen cecum
 Pyramidal lobe
extends superiorly
from the isthmus in
fifty per cent

Thyroid Anomalies
 Thyroglossal Duct Cysts
and Sinuses
– May form anywhere
along the course followed
by the thyroglossal duct
– Most seen by 5 yo
– Asymptomatic unless
infected
– Midline, painless,
moveable neck mass
– Sinuses are open, cysts
are closed

Thyroid Anomalies
 Ectopic Thyroid Gland
– Lingual thyroid
• Result of failure to
descend
• Often only thyroid
tissue present
– Accessory thyroid
tissue
• Tongue
• Neck, superior or lateral
to thyroid

Tongue
 General
– Merged distal tongue buds
 anterior 2/3
– Copula and hypobranchial
eminence  posterior 1/3
– Terminal sulcus divides
anterior and posterior
 Taste buds
– Most are filiform papillae
and are sensitive to touch
 Muscles
– Supplied by XII except for
palatoglossus (X)

Tongue
 Nerves
– Sensory for anterior 2/3 is
from V3 (lingual)
– Chorda tympani (VII) taste
buds for anterior 2/3
(except for vallate papillae
supplied by IX)
– IX supplies posterior 1/3
– X (Superior Laryngeal)
supplies area around
epiglottis

Tongue
 Taste buds
– Most are filiform
papillae and are
sensitive to touch

Tongue Anomalies
 Lingual cysts and Fistulas
– Persistence of thyroglossal
duct open to foramen
cecum
 Ankyloglosia (Tongue-
Tie)
– Short frenulum to tip,
stretches with time
 Macroglossia
– Usually from muscular
hypertrophy or
lymphangioma
 Microglossia
– Associate with
micrognathia and limb
defects (Hanhart’s
syndrome)
 Bifid or Cleft Tongue
(Glossochisis)
– Incomplete fusion of distal
tongue buds  deep
median sulcus

Ear
 Three anterior hillocks of
the first branchial arch
form the tragus, helical
crus, and superior helix
 Three posterior hillocks of
the second branchial arch
form the antihelix,
antitragus, and lobule
 First branchial groove
forms external auditory
meatus
 Microtia
– 1:6000-8000 births
– Associated with hemifacial
microsomia
 Nerves
– Great auricular (C2, C3) 
lower lateral/lower cranial
– Auriculotemporal (V3) 
superolateral/ anterior and
superior external auditory
canal
– Lesser occipital  superior
cranial
– Arnold’s (X) concha /
posterior auditory canal
(referred oropharyngeal
pain)

Ear

Face
 Stomodeum is primitive mouth
 Five facial primordia appear as
prominences around stomodeum
– Single
fronto(forehead)nasal{
most of nose(except
septum/alae)} prominence 
optic vesicles  eyes
– Paired maxillary prominences
 lateral upper lip, most of
maxilla, secondary palate
– Paired mandibular
prominences  chin, lower
lip, lower cheek

Face
 Mandible forms first
 Nasal placodes  nasal
pits
 Six auricular hillocks 
ear
 Epithelial cord canalizes
in nasolacrimal groove 
nasolacrimal duct
– Atresia if canalization fails

Face
 Lateral nasal prominence
 nasal alae
 Medial nasal prominences
merge  intermaxillary
segment  philtrum of
lip, premaxilla (gum),
primary palate, nasal
septum
 Second arch  muscles of
facial expression (VII)
 First arch  muscles of
mastication (V)

Face
 Labiogingival lamina  lips and gingivae,
lingual frenulum
 Changes
– Early fetal period: Flat nose and
underdeveloped mandible
– Enlarging brain: Prominent forehead, medial
movement of eyes and external ears rise

Nasal Cavities
 Nasal placodes 
nasal pits  deepening
 nasal sacs
 Oronasal membrane
separates the oral
cavity from the nasal
sacs
 Membrane ruptures 
primitive chonae
(opening b/w nasal
cavity and
nasopharynx)

Nasal Cavities
 Olfactory system
– Ectodermal
epithelium in the
roof of each nasal
cavity  specialized
 olfactory
epithelium
– Some epithelial cells
 olfactory
receptors (axons
become olfactory
nerve) and grow into
bulbs of the brain

Nasal Cavities
 Paranasal sinuses
– From outgrowths of nasal cavity walls  pneumatic
(air-filled) extensions of the nasal cavities in adjacent
bones
– Original openings of the outgrowths persist as the
orifices of the adult sinuses
– Most are rudimentary in newborns
• Frontal sinuses are visible by seven
• Sphenoidal sinuses usually evident by two
– Vomeronasal cartilage  narrow cartilage strips
between the inferior edge of the cartilage of nasal
septum and vomer

Palate
 Palatogenesis from 5th –
12th week
 Primary Palate
– Median palatine process
begins to develop from
deep intermaxillary
segment of maxilla
– Primary palate forms the
premaxillary part of the
maxilla
– Represents a small part of
the adult hard palate
(anterior to the incisive
foramen that lodges the
incisor teeth)

Palate
 Secondary Palate
– Primordium of hard and
soft palates that extend
posteriorly from the
incisive foramen
– Shelf-like structures
called lateral palatine
processes (palatine
shelves) project
inferiomedially on each
side of the tongue

Palate
– Shelves elongate and
ascend to a horizontal
position superior to the
tongue
– Shelves fuse in a median
plane with nasal septum and
posterior primary palate
– Elevation to the horizontal
position is thought to be
caused by the intrinsic shelf
elevating force by hydration
of hyaluronic acid in the
shelves

Palate
– Nasal septum develops
from downgrowths of
merged medial nasal
prominences
– Fusion between nasal
septum and palatine
processes proceeds
anteriorly to
posteriorly

Palate
– Bone develops in
primary palate forming
the premaxillary part of
the maxilla which
lodges between the
incisor teeth
– Bone extends from the
maxillae and palatine
bones in to the lateral
palatine processes to
form the hard palate

Palate
– Posterior aspects do
not ossify
– Extend posteriorly
beyond nasal septum
and fuse to form the
soft palate and uvula
– Palatine raphe
permanently indicates
the line of fusion of the
lateral palatine
processes

Palate
– Small nasopalatine
canal persists between
premaxilla and palatine
processes as incisive
foramen (openings for
incisive canals)

Clefts
– Lip and palate
• Upper lip and anterior maxilla with or without hard
and soft palate
• Hard and soft palate
– Complete posterior (to incisive foramen) palate
– Anterior cleft anomalies
• Cleft lip, with or without a cleft of the alveolar part
of the maxilla
• Result from deficiency of mesenchyme in the
maxillary prominences and intermaxillary segment

Clefts
 Posterior cleft anomalies
– Clefts of secondary or posterior palate that
extend through the soft and hard palate to the
incisive foramen
– Caused by defective development of the
secondary palate and result from the growth
distortions of the lateral palatine processes
(shelves) which prevent their medial migration
and fusion

Clefts
– Lip
• 1:1000 births, 70% male,
• Caucasion>Asian>Hispanic>AA
• Notches on vermilion border to alveolar maxilla

Clefts
– Unilateral
• Failure of maxillary prominence
on affected side to unite with
merged medial nasal prominences
• Consequence of failure of
mesenchymal masses to merge
and the mesenchyme to proliferate
and smooth out the overlying
epithelium
• Results in persistent labial groove
• Epithelium in the labial groove
stretches and tissues of the floor
breakdown
• Lip is divided into medial and
lateral parts
• Bridge of tissue (Simonart’s band)
joins parts of incomplete cleft lip

Unilateral cleft lip

Clefts
– Bilateral
• Failure of mesenchymal masses in
the maxillary prominences to met
and unite with the merged medial
nasal prominences
• Epithelium in both labial grooves
becomes stretched and breaks
down
• May have varying degrees of
defects on each side
• When there is a complete bilateral
cleft of the lip and alveolar part of
the maxilla, the intermaxillary
segment hangs free and projects
anteriorly
• These defects are deforming
because of loss of continuity with
the orbicularis oris muscle which
purses the lips

Clefts
– Median (rare)
• Upper
– Mesenchymal
deficiency causing
partial or complete
failure of medial nasal
prominences to merge
and form the
intermaxillary segment
– Characteristic of the
Mohr syndrome
• Lower
– Failure of mesenchymal
masses in the
mandibular prominences
to merge completely and
smooth out the
embryonic cleft between
them

Clefts
– Palate
• +/- lip in 1:2500 births, females
• Uvula, soft/hard palate, lip, alveolar maxilla
• Failure of mesenchymal masses in lateral palatine
processes (shelves) to fuse with each other, the nasal
septum and posterior margin of the median palatine
process

Clefts
– Palate (divided by incisive
foramen)
• Anterior
masses in lateral
palatine masses to fuse
with primary palate
• Posterior
masses in lateral
with nasal septum
• Both
masses in lateral
with each other, primary
palate or nasal septum

Craniofacial clefts
 1.4-5.1:100,000
 Numbered 0-14 (sum=14)
– 0-7 are facial
– 8-14 are cranial
 Number 7 is least rare
(1:5600) =hemifacial
microsomia (hypoplasia of
mandibular ramus, hypoplasia
of midface, others) associated
with Goldenhar syndrome
 Bilateral 6,7,8 is complete
form of Treacher-Collins

Others
Facial clefts
Macrostomia
Microstomia
Nasal
Single nostril
Bifid nose
Absence

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