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Learning ObjectivesLearning Objectives
Upon completion of this lecture, the student should be able to:Upon completion of this lecture, the student should be able to:
Understand the fundamental organization of the pharyngealUnderstand the fundamental organization of the pharyngealregion.region.
Understand the steps in the formation of the pharyngealUnderstand the steps in the formation of the pharyngeal(branchial) arches.(branchial) arches.
Know the name and or numbering of the pharyngealKnow the name and or numbering of the pharyngealarches.arches.
Know the nerves, muscles, cartilage, branch of the aortaKnow the nerves, muscles, cartilage, branch of the aortaand skeletal components associated with each pharyngealand skeletal components associated with each pharyngealarch.arch.
Describe the structures formed by the pharyngeal arches,Describe the structures formed by the pharyngeal arches,pouches and grooves.pouches and grooves.
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Suggested ReadingsSuggested Readings
Chapter 16, pages 265-275Chapter 16, pages 265-275
Langmans Medical EmbryologyLangmans Medical Embryology
1111thth edition., 2010edition., 2010
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It is now the 23rd day after fertilization. TheIt is now the 23rd day after fertilization. The
heart just started to beat. Mesoderm has justheart just started to beat. Mesoderm has just
developed into somites and somitomeres. At thedeveloped into somites and somitomeres. At the
front of the embryo, the brain is just developing,front of the embryo, the brain is just developing,and with it, the rest of the head...and with it, the rest of the head...
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The Embryonic GutThe Embryonic Gut
The story of branchial arches begins with the gut tubeThe story of branchial arches begins with the gut tube
itself.itself.
It is pulled anteriorly with the oral (buccopharyngeal)It is pulled anteriorly with the oral (buccopharyngeal)
plate during the early part of neural development.plate during the early part of neural development.
As it pulls forwards, it pulls into a tube whichAs it pulls forwards, it pulls into a tube which
elongates.elongates.
The embryonic pharynx is the part closest to the oralThe embryonic pharynx is the part closest to the oral
plate itself.plate itself.
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As the brain grows rostrally, the gut tube is pulledAs the brain grows rostrally, the gut tube is pulled
anteriorly.anteriorly.
Gut Tube FormationGut Tube Formation
Septum
Transversum
Early Heart
Tube
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Expansion and DifferentiationExpansion and Differentiation
The gut tube then differentiates as it expands.The gut tube then differentiates as it expands.Here, we see:Here, we see:
ForegutForegut
MidgutMidgut
HindgutHindgut
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The Pharynx.The Pharynx.
TheThe pharynxpharynx is in the anterior-most region.is in the anterior-most region.
Yolk Sac Connecting Stalk
Allantois
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Humble Beginnings of the ArchesHumble Beginnings of the Arches
The arches develop as small columns of tissue onThe arches develop as small columns of tissue on
either side of the embryonic pharynx.either side of the embryonic pharynx.
First branchial arch develops first.First branchial arch develops first.
SecondSecond
branchialbranchialarcharch
developsdevelops
next.next.
RostralRostral
neuroporeneuropore
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Early embryo (Neurula stage) showingEarly embryo (Neurula stage) showing
arches, plus eye and ear.arches, plus eye and ear.
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The Arches GrowThe Arches Grow
The first arch bendsThe first arch bends
around the oral platearound the oral plate
and forms two parts:and forms two parts:
Maxillary divisionMaxillary division
Mandibular divisionMandibular division
The second archThe second arch
develops behind itdevelops behind it
Followed by the thirdFollowed by the third
archarch
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The Arches GrowThe Arches Grow
The stomodeum is surrounded by branchial arch 1
structures.
structures. It splits open as the embryo undergoes
further develop.
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This shows the remaining branchial archesThis shows the remaining branchial arches
developing.developing.
Continued Development of the ArchesContinued Development of the Arches
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This shows how the branchial arches develop as the rest ofThis shows how the branchial arches develop as the rest of
the embryo grows. Note that the first two arches formthe embryo grows. Note that the first two arches form
while the cranial neuropore is still open. (Langman,while the cranial neuropore is still open. (Langman,
Medical embryology).Medical embryology).
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To view the next stage,To view the next stage,the head is sectionedthe head is sectioned
right through theright through the
pharynx, and the toppharynx, and the top
removed.removed.
We will be lookingWe will be looking
down on the floor ofdown on the floor of
the embryonic pharynxthe embryonic pharynx
from the inside.from the inside.
Continued Development of the ArchesContinued Development of the Arches
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Inside the Embryonic PharynxInside the Embryonic Pharynx
The pharynx is seen fromThe pharynx is seen fromaboveabove
contains midlinecontains midline
structures (developingstructures (developing
tongue, larynx, etc.) astongue, larynx, etc.) as
well as branchial arches.well as branchial arches.
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Midline StructuresMidline Structures
Stomodeum (mouth)Stomodeum (mouth)
Anterior 2/3 of tongueAnterior 2/3 of tongue
Foramen cecumForamen cecum
Posterior 1/3 of tonguePosterior 1/3 of tongue
Epiglottic swellingEpiglottic swelling
Laryngotracheal grooveLaryngotracheal groove
EsophagusEsophagus
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Orientation to Branchial archesOrientation to Branchial arches
BA I Maxillary partBA I Maxillary part
BA I Mandibular partBA I Mandibular part
BA II (Hyoid)BA II (Hyoid)
BA IIIBA III
BA IVBA IV
note, no BA Vnote, no BA V
BA VIBA VI
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Structures within the Branchial ArchesStructures within the Branchial Arches
CartilageCartilage
Aortic archAortic arch
Cranial nerveCranial nerve
MuscleMuscle
Pharyngeal pouchPharyngeal pouch
Branchial grooveBranchial groove
(cleft)(cleft)
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Aortic Arch DerivativesAortic Arch Derivatives
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Aortic Arch DerivativesAortic Arch Derivatives
AA 1: degeneratesAA 1: degenerates
AA 2: degeneratesAA 2: degenerates
AA 3: Carotid arteriesAA 3: Carotid arteries
AA 4:AA 4:
Left-arch of aortaLeft-arch of aorta
Right-subclavianRight-subclavian
AA 6: Pulmonary AAAA 6: Pulmonary AA
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Aortic Arch DerivativesAortic Arch Derivatives
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Aortic Arch DerivativesAortic Arch Derivatives
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Aortic arches and pharyngeal pouches in an
embryo. (Langman, Medical Embryology)
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Cranial Nerve DerivativesCranial Nerve Derivatives
BA 1:BA 1: MaxillaryMaxillary divisiondivision
of trigeminalof trigeminal
BA 1:BA 1: MandibularMandibular
division of trigeminaldivision of trigeminal
BA 2 Facial NerveBA 2 Facial Nerve
BA 3: GlossopharyngealBA 3: GlossopharyngealNerveNerve
BA 4/6: Vagus NerveBA 4/6: Vagus Nerve
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Cranial nerves in the developing embryo.
Langman, Medical Embryology.
M l D i i
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Muscle DerivativesMuscle Derivatives
BA 1: Muscles ofBA 1: Muscles of
MasticationMastication
BA 2: Muscles of facialBA 2: Muscles of facial
expressionexpression
BA 3: StylopharyngeusBA 3: Stylopharyngeus
MuscleMuscle
BA 4: Muscles of larynxBA 4: Muscles of larynx
and pharynx.and pharynx.
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Bone and CartilageBone and Cartilage
Bones which develop include facial bones as wellBones which develop include facial bones as well
as bones and cartilage in the visceral part of theas bones and cartilage in the visceral part of theneck.neck.
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Bone and CartilageBone and Cartilage
Bones which develop include facial bones as wellBones which develop include facial bones as well
as bones and cartilage in the visceral part of theas bones and cartilage in the visceral part of theneck.neck.
Branchial Groo e/Phar ngeal Po chBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives
PharyngealPharyngeal
pouch 1:pouch 1:
middle earmiddle earand auditoryand auditory
tube.tube.
BranchialBranchial
groove 1:groove 1:
externalexternal
auditoryauditory
meatusmeatus
Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives PharyngealPharyngeal
pouch 2:pouch 2:Palatine tonsilPalatine tonsil
Behind 2ndBehind 2nd
arch, branchialarch, branchial
grooves fusegrooves fuse
into a cervicalinto a cervical
sinus, whichsinus, which
disappearsdisappears
(occasionally(occasionally
forms cyst)forms cyst)
PharyngealPharyngeal
pouch 3:pouch 3:Parathyroid,Parathyroid,
thymusthymus
PharyngealPharyngeal
pouch 4/5:pouch 4/5:
Parathyroid,Parathyroid,
C-cells ofC-cells of
thyroidthyroid
Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives
Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives
Tympanic cavityTympanic cavity Auditory tubeAuditory tube
ExternalExternal
auditoryauditory
meatusmeatus
Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives
Palatine TonsilPalatine Tonsil
Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives
Parathyroid (inferior)Parathyroid (inferior)
CervicalCervical
sinussinus
ThymusThymus
Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
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Branchial Groove/Pharyngeal PouchBranchial Groove/Pharyngeal Pouch
DerivativesDerivatives
ParathyroidParathyroid
(superior)(superior)Ultimobranchial bodyUltimobranchial body
Branchial Groove/Pharyngeal Pouch DerivativesBranchial Groove/Pharyngeal Pouch Derivatives
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Branchial Groove/Pharyngeal Pouch DerivativesBranchial Groove/Pharyngeal Pouch Derivatives