The Branchial Arches - University of Malta
Transcript of The Branchial Arches - University of Malta
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The Branchial Arches
Professor Alfred CuschieriDepartment of Anatomy
University of Malta
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In the 4-week embryo, the primitive pharynx is associated with paired arches and pouches
Primitive pharynx
• Pharyngeal pouches - lateral pockets of endoderm
• Branchial clefts - corresponding pockets of
ectoderm
• Branchial arches - intervening mesodermal
thickenings
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• A cartilage• A cranial nerve• An aortic arch• Myoblasts
Each branchial arch contains:
These elements are of neural crest origin
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In fish there are 6 pairs of branchial arches, but only four are well developed in humans
• The fifth branchial arch fails to develop
• The sixth branchial arch is rudimentary
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The first two arches and their cartilages are named
1st - Mandibular arch & its maxillary process
3rd arch4th arch
- containsMeckel’s cartilage
2nd - Hyoid arch-contains Reichert’s cartilage
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Derivatives of the first, second and third arch cartilages
1st arch (Meckel’s) cartilage forms the:• Incus • Malleus• Sphenomandibular ligament• Lingula of mandible
The mandible ossifies in membrane from the mesoderm around Meckel’s cartilage
2nd arch (Reichert’s) cartilage forms the:
3rd arch cartilage forms the:• Greater cornu & part of body of hyoid bone
•Stapes• Styloid process• Stylohyoid ligament• Lesser cornu & part of body of hyoid bone.
4th arch cartilage forms the:• Laryngeal cartilages
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Each Branchial Arch Is Supplied by a Cranial Nerve.
•Muscles of mastication•Tensor veli palatini•Tensor tympani•Mylohyoid•Anterior belly of digastric
1st arch Mandibular nerve
2nd arch Facial nerve
•Muscles of facial expression•Stapedius•Stylohyoid•Posterior belly of digastric
3rd arch - Glossopharyngeal n. • Stylopharyngeus4th arch - Vagus nerve • Pharyngeal & laryngeal m.
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The nerves of the 1st & 2nd arches give a sensory branch to the preceding arch
Maxillary nerve - sensory
Mandibular nerve - motorChorda tympani n -sensory
Facial nerve - motor
Glossopharyngeal nerve - motor
Vagus nerve - motor
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Derivatives of branchial clefts and pharyngeal pouches
1st cleft - external auditory meatus
2nd arch overgrows all other arches Branchial sinus
Pouches1st – pharyngotympanic tube2nd - tonsil 3rd – thymus and inferior parathyroid4th – superior parathyroid
- ultimobranchial body C-cells of thyroid
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Development of Tongue
Thyroid diverticulum(foramen caecum)
1st archMandibular nerve
3rd arch Glossopharyngeal nOvergrows other arches
Anterior 2/3
Posterior 1/3
Tuberculum impar
Cupola
Aryepiglottic swelling
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The head develops in relation to the special sense placodes
Otic placode
Lens placode
Olfactory placode
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Development of the eye
Optic vesicleLens placode
Pigmented epitheliumNeurosensory epithelium
Iris & Ciliary body
Lens
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Rudiments of faceFrontal process overlying forebrain
Fronto-nasal process
Maxillary process
Medial nasal processLateral nasal processNasal pit
Mandibular arch