simple and detailed

2. PRIYONA JOHN
1ST year PG
DEPARTMENT OF PAEDODONTICS
& PREVENTIVE DENTISTRY

3. CONTENTS
• Introduction
• Evolution of branchial arches.
• Normal development of branchial
arches.
• Derivatives of branchial system.
- First branchial arch.
- Second branchial arch.
- Third branchial arch.
- Fourth branchial arch.
-Sixth branchial arch

4. • Anomalies of development of
branchial arches.
• Branchial pouches;
-Normal development of
branchial pouches
-First branchial pouch.
-Second branchial pouch.
-Third branchial pouch.
-Fourth branchial pouch.

5. • Branchial cleft.
• Molecular regulation of facial
development.
• Anomalies of development of
branchial pouches and cleft.

6. INTRODUCTION
• Pharyngeal arches are rod like
thickenings of mesoderm present in the
wall of foregut.There are six pairs of
pharyngeal arches, in which the fifth one
is rudimentry.
• Mesenchyme for the formation of the
head region is derived from paraxial
and lateral plate mesoderm,neural crest
cells and thickened region of ectoderm
known as ectodermal placodes.

7. Paraxial mesoderm
• The mesoderm on either side of the
notochord becomes thick and is
called paraxial mesoderm.
• The paraxial mesoderm segmented
into cubical masses called
somitomeres which give rise to
somites.
• Somites:It lies on the either side of
developing neural tube.

8. Lateral plate mesoderm
• More laterally, the mesoderm forms a
thinner layer called lateral plate
mesoderm.

9. Neural crest cells
• Pluripotent cells.
• Great migratory properties.
• Migration of cells can be
translocations(resulting of dislocation
of tissues)or active cell migration.
• Being pluripotent, display varying
regional characteristics at their
destination sites.

10. • Neural crest cells remaining rostral and
dorsal to the forebrain contribute to the
leptomeninges and parts of skull.
• Those around mid brain form part of
trigeminal ganglion.
• Neural crest cells migrating caudally and
ventrally encounter the pharyngeal
endoderm that induces formation of
pharyngeal arches.

11. • Many pharyngeal derivatives, including
facial bones are of neural crest origin.
• Cells migrate within cranial paraxial
mesoderm form somitomeres, which
provides muscle of the face and jaw.

12. Development and evolution of
branchial arches
• In all vertebrates, pharyngeal apparatus
develops from a series of bulges found on
lateral surface of head.The pharyngeal arches
consists of number of embryonic cell types.
• Each arch has:
1.Externally covering ectoderm.
2.Internally covering endoderm between these
mesenchymal filling of neural crest with
central core of mesoderm.

13. • Different embryonic population
produce different components of the
arch.
• Ectoderm –Epidermis and sensory
neurons of epibranchial ganglia.
• Endoderm –Epithelial lining of the
pharynx and forms the taste buds as
well as the thyroid and parathyroid
and thymus.

14. • Neural crest cells forms –skeletal and
connective tissue .
• Mesoderm forms musculature and
endothelial cells.
• In all gnathostomes:
First arch-jaw
Second arch-hyoid apparatus
• More caudal arches-gills in fish and
throat in amniotes.

16. Developmental basis of the
evolution of the vertebrae
pharynx.
The transition from prochordates to
vertebrates:
• Neural crest cells produce a key role
in the evolution of vertebrate pharynx.
• Yet the evolution of the vertebrate
pharynx was not driven exclusively by
the crest, but is rather integration of
signals.

17. • In chick, pharyngeal arches can form
and are patterned in absence of neural
crest cells reflects the evolutionary
history of arches.
• Pharyngeal segmentation is a general
chordate feature.
• But in the presence of neural crest or
more specifically ectomesenchymal
crest is a vertebrate feature.

18. • The one substantial difference between
the vertebrates pharyngeal arches and
those of prochordates is the presence of
epibranchial placodes.

19. The transition from agnatha
to gnathostomes.
• The segregation of the neural crest cells
into 3 streams, each endowed with a
distinct identity has been proposed as
being an important event in the of
gnathostomes.(Graham et al.1993)
• However a recent study of lamprey crest
has found that even though this animal
is jawless its pharyngeal crest is also
organized into three.(Horigome et
al.1999)

20. Transition to tetrapods
• Key changes occurred at caudal end
of the pharynx, and they are all likely
to have been driven by changes in the
endoderm.

22. Normal development
• In the 4th week of IUL, after establishment of
the head fold, the foregut is bounded
ventrally by the pericardium, dorsally by the
developing brain, cranially it is first
separated from stomatodeum by
buccopharyngeal membrane when this
membrane breaks down, the foregut open to
exterior through stomatodeum.

23. • The neck is formed by the elongation of the
region between the stomatoduem and
pericardium this is achieved partly by the
descent of developing heart.
• However this elongation is due to the
appearance of series of mesodermal
thickenings in the wall of cranial most part of
the foregut.
• These are called pharyngeal or branchial
arches.

25. • At this stage ;
- Head is represented by bulging
caused by the developing brain.
- Pericardium –future thorax.
- Stomatodeum –future mouth.

26. BRANCHIAL ARCH COMPONENTS
• Muscular components.
• Skeletal components.
• Cranial nerve.
• Arterial component.

30. First branchial arch
• Also called mandibular arch.
• Precursor of both maxilla and
mandible.
• The maxilla is derived from a small
maxillary prominence extending
cranioventrally from much larger
mandibular prominence derived from
first arch.

31. Skeleton components
• Meckels cartilage.
• The ear ossicle malleus and incus.
MECKELS CARTILAGE:
• Arises at 41st to 45th day of post
conception.
• Provides template for development of
mandible.

32. • Most of the cartilage substance of
meckels cartilage disappears in
formed mandible.
• Mental ossicle is the only portion of
the mandible derived from the
meckels cartilage by endochondral
ossification.

33. • During further development meckels
cartilage disappears expect for two
small portions at its dorsal end that
persist and form (head and neck of
malleus) and the body and short crus
of the incus.
• Two ligaments:
-The anterior ligament of malleus.
- The sphenomandibular ligament.

34. Muscular components
• Originating from cranial somitomere 4.
• Muscles are:
-Muscles of mastication.
-The mylohyoid muscle.
-The anterior belly of digastric.
-The tensor tympani.
-Tensor veli palatini.

35. Nerve of the arch.
• Mandibular division of trigeminal
nerve.
• The sensory component of this nerve
innervates the mandible and its
covering mucosa and gingiva, the
mandibular teeth, anterior two thirds
of tongue, floor of mouth and skin of
the lower third of face.

36. Artery of the arch
• The first arch artery contributes in part
of the maxillary artery and part of
external carotid artery.

37. SECOND BRANCHIAL ARCH
• Also known as hyoid arch.
• Cartilage of second arch is Reichert’s
cartilage.
REICHERTS CARTILAGE:
• It appears on the 45th to 48th days of
post conception.

38. • Reicherts cartilage attaches to
basicranial otic capsule where it is
grooved by facial nerve, it provides the
remaining cartilaginous circumference to
labyrinthine and tympanic segments of
the facial canal.

39. Skeleton components
1. Reicherts cartilage.
2. Styloid process of temporal bone.
3. The stapes.
4. Lesser horn and cranial part of body
of the hyoid bone.
5. Stylohyoid ligament.

40. MUSCULAR COMPONENTS
• Muscles of second arch originates from
cranial somitomere 6.
• Muscles are:
-Stylohyoid.
-Posterior belly of digastric.
-Muscles of facial expression.
-Stapedius.

42. Nerve of the arch:
- Facial nerve.
Artery of the arch :
- Stapedial artery.
Stapedial artery
- Derived from second aortic arch.
- Which disappears during fetal
period, leaving foramen in stapes.

43. • A Branch of internal carotid artery, the
stapedial artery initially supplies the
deep portion of face, an area is taken
over by branches of external carotid
artery once the stapedial artery
disappears.

44. THIRD BRANCHIAL ARCH
Skeleton components:
• The greater horn and the caudal part
of the body of the hyoid bone.
• The reminder of the cartilage
disappears.
Muscular components:
• Muscles of this arch originating from
cranial somitomere 7.
• It forms stylopharyngeus muscle.

45. Nerve of the arch
• Glossopharyngeal.
• The mucosa of the posterior third of
the tongue is derived from this arch,
accounting for its sensory innervation
by glossopharyngeal nerve.

46. Artery of the arch
• Common carotid and part of internal
carotid artery.

47. • Neural crest tissue in the third arch
forms carotid body, which first
appears as a mesenchymal
condensation around the third aortic
arch artery.
• This chemoreceptor body derives
nerve supply from glossopharnygeal
nerve.

48. FOURTH BRANCHIAL ARCH
• Fourth arch forms the thyroid
cartilage.
Muscular components:
• Muscles originating from occipital
somites 2 and 4.

49. • It forms:
- Constrictors of pharynx.
- Palatopharyngeus.
- Palatoglossus muscle of tongue
- Levator veli palatini.
- Uvular muscles of soft palate.

50. Nerve of the arch:
• Superior laryngeal branch of 10th
cranial nerve.
Artery of the arch:
Fourth arch artery
Left side Right side
Arch of aorta. Brachiocephalic.
LEFT SIDE RIGHT SIDE

52. SIXTH PHARYNGEAL ARCH
• Cartilage of sixth arch probably forms
cricoid and arytenoid cartilages of
larynx.
Muscular components:
• From occipital somites 1 and 2.
• Forms intrinsic muscles of larynx.

53. Nerve of the arch:
• Recurrent laryngeal branch of vagus
nerve.
Artery of the arch:
• Pulmonary arteries.
• Ductus arteriosus.

54. ANOMALIES OF THE
BRANCHIAL ARCH
• Deficient development of pharyngeal
arches results in syndromes that are
identified according to the arches.
• The first and second branchial arch
syndrome includes array of defects
involving not only those derivatives of
first and second arches and cleft but
also primordia of the temporal bone.

56. Most common abnormalities are:
• Underdevelopment of external ear,
middle ear ossicles, the condyle, the
ramus, the zygomatic arch and the
malar bone and the temporal bone
expect for the petrous section.
• Muscles of mastication and facial
expression are affected.

57. • Clinical appearance of macrostomia
and seventh cranial nerve paresis.
• One or more accessory auricles are
present along the oro-tragal line.
• Necrotic facial dysplasia.
• Hemifacial Microsomia and Microtia.
• Otomandibular dysostosis.
• Unilateral facial agenesis.

58. • Intrauterine facial necrosis.
• Hemignathia.
• Microtia syndrome.
• Berry Treacher Collins syndrome.
• Goldenhars syndrome.
• Hallerman Streiff syndrome.
• Eagle syndrome.
• Pierre Robin syndrome.

59. Berry Treacher Collins Syndrome
• Also known as mandibulofacial
dysostosis.
• Bird like or fish like faces.
Clinical features:
-Hypoplasia of facial bones especially
malar and mandible.
-Malformation of external ear, middle
and internal ear.

60. • Macrostomia, high palate and abnormal
position and malocclusion of teeth.
• Blind fistulas between angles of the ears
and angles of the mouth.
• Facial clefts and other skeleton
deformities.

61. • In Germany following the
administration of thalidomide to
woman in the first 6 weeks of
pregnancy between 1959 and 1962 at
least 1000 severe cases and up to
2000 less severe cases of defects of
the first and second branchial arches
were observed in their offspring.

62. PHARYNGEAL POUCHES
• There are four pairs of pharyngeal
pouches.
• Fifth one is rudimentry .

63. 

64. Normal development of
pharyngeal pouches.
In late embryonic period
Dilation of the cranial end of the
foregut, that lying between
developing head ventrally and the
developing chondrocranium
rostrodorsally. It leds to formation of
the primitive pharynx.

65. Then the lateral aspect of the
elongated primitive pharynx project a
series of pouches between the
pharyngeal arches.
Formation of pharyngeal/branchial
pouches.

66. • Pharyngeal pouches sequentially
decrease in size craniocaudally.
• Pharyngeal pouch is lined by foregut
endoderm.

68. FIRST PHARYGEAL POUCH
• Pouch has ventral and dorsal
surfaces.
• Ventral portion is obliterated by
developing tongue.
• Dorsal diverticulum deepens laterally
as the tubotympanic recess to form
auditory tube.
• Widening of the auditory tube end into
tympanum/middle ear cavity.

69. • Tympanum/middle ear cavity
occupied by the dorsal ends of the
cartilages of the first and second
pharyngeal arches that develops into
ear ossicle.
• Tympanum maintains contact with
pharynx via the auditory tube
throughout life.

70. SECOND PHARNYGEAL
POUCH
• Ventral portion obliterated by the
developing tongue.
• The epithelial lining of pharyngeal
pouch proliferates and forms buds
that penetrate into surrounding
mesenchyme.
• The buds are secondarily invaded by
mesodermal tissue forming the
primodium of palatine tonsils.

71. • During the 3rd and 5th months, the
tonsil is infiltrated by the lymphatic
tissue.
• Part of the pouch remains and is
found in the adult as tonsillar fossa.

72. THIRD PHARYNGEAL POUCH
• Thymus and inferior parathyroid gland
formed from third pouch.
• The distal extremity has a dorsal and
ventral wing.
• In the 5th week, epithelium of dorsal
region differentiates into inferior
parathyroid gland.

74. Ventral surface epithelium differentiates
from each side it migrates and forms two
elongated diverticula
it grows caudally into surrounding
mesenchyme to form the elements of
thymus gland.

75. • The two thymic rudimentary from
each side meets in the mid line but do
not fuse, united by connective tissue.
• Lymphoid cells invade thymus from
hemopoietic tissue during the 3rd
month of post conception.

76. • Growth and development of thymus
continue until puberty.
• In young child the thymus occupies
considerable space in the thorax and
lies behind the sternum and anterior
to the pericardium and great vessels.
• In older patient it is atrophied and
replaced by fatty tissue.

77. FOURTH PHARYNGEAL
POUCH
• Epithelium of dorsal region forms
superior parathyroid gland .
• Epithelium of ventral surface forms
ultimobranchial body.
• When the parathyroid gland loses
contact with wall of pharynx, it
attaches itself to dorsal surface of the
caudally migrating thyroid as superior
thyroid gland.

78. ULTIMOBRANCHIAL BODY
• Later incorporated in thyroid gland.
• Cells of ultimobranchial body give rise
to parafollicular or C-cells.
• C cells secrete calcitonin it regulates
Ca level in blood.

79. BRANCHIAL CLEFT or GROOVES
• These grooves separate the
pharyngeal arches externally.
• Out of four pairs, only first pair
persists as the external acoustic
meatus.
• Active growth of the 2nd arch
mesoderm overlaps 3rd and 4th
arches.

81. Molecular regulation
• Neural crest cells arise from the
neuroepithelial cells adjacent to the
surface ectoderm all along the edges
of neural folds.
• In the hind brain the crest cells
originate in a specific pattern from
segments called rhombomeres.
• There are 8 segments in the hind
brain R1-R8.

82. • Neural crest cells from specific
segments migrate to populate specific
pharyngeal arches.
• R1&R2 cells migrate to first arch.
• R4 cells to second arch.
• R6 &R7 fourth and sixth arch.
• Neural crest cells that populate the
pharyngeal arch form the skeletal
components.

83. • It is divided by three streams:

84. • Pouches are formed by migrating
endoderm cells laterally, this
migration is stimulated by fibroblast
growth factors.(FGF’s)
• As pouches form they express a very
characteristic pattern of genes.
- BMP7-posterior ectoderm of each
pouch .

86. • FGF8-lies in the anterior ectoderm.
• PAX1-dorsal most endoderm of each
pouch.
• SHH – posterior endoderm of second
and third arch.
• Function of these genes is regulate
differentiation and patterning of
pharyngeal arch mesenchyme into
specific skeletal structures.

87. • Previously it was thought that neural
crest cells regulated the patterning of
these skeletal elements but its clear
that this process is controlled by
pharyngeal pouch endoderm.
• Formation of pharyngeal pouches
prior to neural crest cells.

88. • In this process there is epithelial
mesenchymal interaction.
• The response of the mesenchyme to
endodermal signals is dependent on
the transcription factors expressed in
that mesenchyme.
• Transcription factors include HOX
gene &other caused by neural crest
cells into arch.

89. • First arch is HOX negative but does
express OTX2.
• OTX2: orthodenticle homeobox 2
- Subfamily of HOX gene.
- Containing transcription factor
that is expressed in midbrain.
• Second arch by HOXA2.

90. • Third arch to sixth arch express by
the members of paralogus group of
HOX genes.ie
HOXA3,HOXB3,HOXD3.

91. ANOMALIES OF
DEVELOPMENT BRANCHIAL
POUCHES AND CLEFT
• Branchial anomalies are composed of
heterogeneous group of congenital
malformations.
• That arise from incomplete
obliteration of pharyngeal cleft and
pouches.
• Second most common congenital
head and neck lesion found in
children.

92. • Branchial arch anomalies may
present as cysts, sinus, fistula or
cartilaginous remnants.
• Sinus: Is a blind ending tract and in
context of branchial arch anomaly
may connect either with skin
(branchial cleft sinus) or with pharynx
(branchial pouch sinus).

93. • Fistula: Communication between two
epithelial surface with regard to
branchial arch anomalies, requires
communication between a persist pouch
and cleft.
• If there is no communication occurs with
inner mucosa or outer skin, then trapped
branchial arch remnant forms cyst.

94. • Second brachial cleft lesion accounts for
95%of common.
• First branchial cleft lesion comprises
only 1%.
• Third and fourth branchial cleft lesion
are quite rare.

96. FIRST CLEFT ANOMALIES
ANATOMY
• Course close to parotid gland
particularly the superficial lobe.
• The tract may pass above, between
or below the branches of facial nerve.

97. • Anomaly is classified by Work in 1972
Classification
Type I Type II
Type I:
• Duplication of membraneous external
auditory canal.
• Contains ectodermal elements only.
• The cyst is located within the parotid
gland.

99. Type II:
• Lesions are composed of ectoderm and
mesoderm therefore may contain
cartilage.
• Pass medial to the nerve and may
present as preauricular, infraauricular, or
post auricular swellings or cysts inferior
to angle of mandible.

100. Clinical features
• They commonly found in girls.
• Cleft remnants appears as a cyst,
sinus, or fistula.
• Between the external auditory canal
and submandibular.
Symptoms:
a)Cervical symptoms.
b)Parotid symptoms.

101. c) Auricular symptoms.
Cervical symptoms:
• Drainage from pit like depression at
the angle of the mandible.
• If the tract becomes infected it can
cause submandibular adenitis.

102. Parotid symptoms:
• Present as a mass and noticed due to
rapid increase in size caused by
inflammation.
Auricular symptoms:
• Otorrhea with a mucous or purulent
discharge from the ear.

103. Histopathology
• Both respiratory and squamous
epithelium alone or in combination may
line branchial lesion.
• Cyst are more lined by squamous
epithelium.
• Sinus and fistulae are more likely to
contain ciliated columnar epithelium.
• Cholestrol crystals.
• Squamous cell carcinoma has been
reported.

104. Treatment
• Likely to require dissection of the
facial nerve and superficial
parotidectomy.
• Additionally it is necessary to excise
the involved skin and cartilage of
external auditory canal.
• Acute infections should be treated
with antibiotics and needle aspiration.

105. SECOND CLEFT ANOMALIES
Anatomy
• Anomalies pass close to glossopharyngeal
and hypoglossal nerves and then enter into
pharynx at the level of tonsillar fossa.
• Present within the submandibular space but
they can occur anywhere along the course of
second branchial arch tract which extends
from the skin overlying supraclavicular fossa
between ICA &ECA.

106. Classification by Bailey in 1929
• Type I
• Type II
• Type III
• Type IV

107. Type I

108. Type II

109. Type III

110. Type IV

111. Clinical features
• A fistula or cyst found in the lower,
anterior lateral region of neck.
CYST FISTULA
3 -4th decade. Infancy or childhood.
Non tender mass in neck. Chronic drainage from an
opening along the anterior
border of SCM in the lower
third of neck.
Can lead to respiratory
distress, torticollis,and
dysphagia.

112. Treatment
• Complete surgical excision by a
transverse cervical incision within the
natural skin fold.

113. THIRD CLEFT ANOMALIES
Anatomy
• There are found along the anterior border
of SCM and pass deep to the internal
carotid artery and glossopharyngeal nerve
and superficial to superior laryngeal nerve,
opening internally in base of pyriform
fossa.

114. Clinical features
• Are uncommon.
• Most seen on the left side of the neck.
• Cyst have been reported to cause
hypoglossal nerve palsy when they
become infected.

115. Treatment
• Complete surgical excision by a
transverse cervical incision.
• Chemo –cauterization.

116. FOURTH CLEFT ANOMALIES
Anatomy
• The course of the tract depends on
which side it occurs,
• On right side,
lesions loop around the subclavian
Pass deep to internal carotid artery

117. Ascending to the level of hypoglossal nerve
Descends along the anterior border of SCM
Enters the pharynx at the level of pyriform
apex or cervical esophagus.

118. On left side:
loops over the anterior aortic arch, medial
to ligamentum arteriousus.
The tract descends into the mediasternum

119. Clinical features
• Extremely rare.
• Present as cyst in the lateral lower
third of the neck.
• Present with infection and manifest
with suppurative thyroiditis.

120. Treatment
• Ipsilateral hemithyroidectomy.
• Partial resection of thyroid cartilage.

121. References
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• Inderbir singh –Human embryology 8th
edition.
• T.W Sadler -Langmans medical embryology
12th edition.
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2006;15:64-69
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biology.2010;(21):325-332.

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