Pharyngeal (Branchial) Apparatus (Page 59) Dr. Sherif Fahm
Pharyngeal (Branchial) Apparatus
(Page 59)
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Pharyngeal (Branchial) Arches• They are 6 mesodermal thickenings on both sides of
pharynx.• They appear in the 4th and 5th 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
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Processes of the 1st archFirst arch has 2 processes:1- Maxillary process.2- Mandibular process.
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Dr. Sherif Fahmy
Mandibular process
Maxillary process
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Maxillary process
Mandibular process
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Maxillary process
Mandibular process
2nd arch Dr. Sherif Fahmy
Maxillary process
Mandibular process
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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.
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Cranial Nerve Related to Pharyngeal Arches
Dr. Sherif Fahmy
Dr. Sherif Fahmy
Each arch has a nerve supply:-Mandibular & Maxillary n. supplies derivatives of 1st arch.-Facial n. supplies derivatives of 2nd arch.-Glossopharyngeal n. supplies derivatives of 3rd arch.-Superior laryngeal br. of vagus supplies derivatives of 4th arch.-Recurrent laryngeal n. supplies derivatives of 6th 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.
Dr. Sherif Fahmy
Dr. Sherif Fahmy
EctodermEndoderm
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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Cleft
Pouch
Cartilage
Nerve supply of the arch
Aortic arch
Pretrematic nerve
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Derivatives of Pharyngeal Arches
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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 2nd 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
Dr. Sherif Fahmy
Fate of Pharyngeal PouchesArch 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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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