Pharyngeal "Branchial" Arches (Special Embryology)

Pharyngeal "Branchial" Arches

1. Pharyngeal (Branchial)
Apparatus
(Page 59)
Dr. Sherif Fahmy

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3. Dr. Sherif Fahmy

4. Pharyngeal (Branchial) Arches
•They are 6 mesodermal thickenings on both sides of
pharynx.
•They appear in the 4
th
and 5
th
weeks.
•Arches are covered with ectoderm (externally) and
lined with endoderm (internally).
•Arches are separated from each other by 4 clefts on
outer surface which is covered with ectodermal
cells.
•Arches are separated from each other by 5 pouches
on inner aspect (cavity of pharynx) which are lined
with endodermal cells.
Dr. Sherif Fahmy

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7. Processes of the 1
st
arch
First arch has 2 processes:
1- Maxillary process.
2- Mandibular process.
Dr. Sherif Fahmy

8. Dr. Sherif Fahmy
Mandibular process
Maxillary
process
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9. Maxillary process
Mandibular process
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10. Maxillar
y
process
Mandibular
process
2
nd
arch
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11. Maxillary
process
Mandibular
process
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12. Structure of each arch
•Each arch is composed of
mesodermal (mesenchymal) cells
that give rise to bones, cartilages
and muscles.
•Each arch has an arterial supply
which is called aortic arch.
•Each arch has a cranial nerve.
Dr. Sherif Fahmy

13. Cranial Nerve Related
to Pharyngeal Arches

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Dr. Sherif Fahmy

15. Each arch has a nerve supply:
-Mandibular & Maxillary n. supplies
derivatives of 1
st
arch.
-Facial n. supplies derivatives of 2
nd
arch.
-Glossopharyngeal n. supplies derivatives
of 3
rd
arch.
-Superior laryngeal br. of vagus supplies
derivatives of 4
th
arch.
-Recurrent laryngeal n. supplies
derivatives of 6
th
arch.
N.B. Pre-trematic nerve crosses from one arch
to other, e.g. chorda tympani n.(branch of
facial n.) supplies anterior 2/3 of tongue.

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17. Dr. Sherif Fahmy
Ectoderm
Endoderm
Cleft
Pouch
Cartilage
Aortic
arch
Nerve supply
Floor of pharynx
Coronal section of neck showing
structure of pharyngeal arches
Thickened
mesoderm
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18. Cleft
Pouch
Cartilage
Nerve supply
of the arch
Aortic arch
Pretrematic nerve
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19. Derivatives of
Pharyngeal Arches

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21. Fate of Pharyngeal Clefts
•Clefts are present on outer surface between
the arches, covered with ectoderm.
•Dorsal part of first cleft forms external
auditory meatus and outer layer of ear drum.
•Downward growth of 2
nd
arch will cover the
other clefts with a space inbetween called
cervical sinus.
•Cervical sinus becomes smaller till it is
completely obilterated.
Dr. Sherif Fahmy

22. Dr. Sherif Fahmy

23. Fate of Pharyngeal Pouches
Arch Ventral partVentral part Dorsal partDorsal part
First pouch
Occupied by
developing tongue.
Tubo-tympanic recess
that gives rise to midlle
ear & Eustachian tube
Second pouch
Occupied by
developing tongue
Palatine tonsile
Third pouch
Thymus gland Inferior parathyroid
gland
Fourth pouch
Unknown Superior parathyroid
gland
Fifth pouch
Ultimo-branchial
body which form
parafollicular cells
in thyroid
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25. Congenital Anomalies
•Ectopic thymic present in neck
•Ectopic parathyroid tissue especially inferior
parathyroid gland.
•Branchial cyst: Remenant of cervical sinus.
•Branchial fistula: Remenant of cervical sinus
that communicates with skin through extenal
fistula, while if it communicates with pharynx
it forms internal fistula.
Dr. Sherif Fahmy