Branchial Arches F11 SV Revised(1)

8/2/2019 Branchial Arches F11 SV Revised(1)

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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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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 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



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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)


pouch 3:pouch 3:Parathyroid,Parathyroid,

thymusthymus


pouch 4/5:pouch 4/5:

Parathyroid,Parathyroid,

C-cells ofC-cells of

thyroidthyroid



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Tympanic cavityTympanic cavity Auditory tubeAuditory tube

ExternalExternal

auditoryauditory

meatusmeatus



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Palatine TonsilPalatine Tonsil



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Parathyroid (inferior)Parathyroid (inferior)

CervicalCervical

sinussinus

ThymusThymus



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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

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Branchial Arches F11 SV Revised(1)