• Forms the anatomical bases for head & neck development
  • Related to gill (brachial system) & located near the developing pharynx (pharyngeal) of the embryo.

The branchial apparatus consists of:

  • Branchial (pharyngeal) arches
    • mesoderm
  • Branchial (pharyngeal) clefts
    • ectoderm
  • Pharyngeal pouches
    • endoderm
    • Simultaneous with the development of the arches & clefts
      • a number of outpocketings arise in the lateral wall of the pharyngeal gut
    • these pouches penetrate the surrounding mesoderm
      • but do not make open communication with the external clefts
  • Branchial membranes
    • ectoderm
    • endoderm

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Branchial (Pharnygeal) arches

  • Develop during the 4th week as rounded ridges on each side of the future head & neck region
  • 4 arches appear by the end of 4th week
    • separated from each other externally by grooves – branchial clefts
  • Function
    • support the lateral walls of the primitive pharynx
    • play an important role in formation of the face & neck
  • The mouth initially appears as a slight depression in the surface ectoderm
    • stomodaeum
    • at 1st separated from the primitive pharynx by the buccopharyngeal membrane

Branchial arches – Components

Each arch has a mesodermal core covered externally by ectoderm & internally by endoderm.

Neural crest cells migrate into the arches & give rise to skeletal components. The mesoderm of each arch gives rise to muscles.

A typical arch contains the following

  • A cartilaginous bar
  • A muscle element
  • An artery
  • A nerve

* REFER PRINTED NOTES ON THE ARCHES, CLEFTS, POUCHES, TONGUE & THYROID GLAND FORMATION

1) 1st branchial arch (Mandibular arch)

Clinical anatomy

  • Malformations result from deficiencies in components of the arch (primarily neural crest migration)
    • Treacher-Collins Syndrome (mandibulofacial dyostosis)
      • no ossification
        • abnormal external, middle and inner ear
      • no development of mandible
        • mandibular & malar hypoplasia
      • lower eyelid defects
    • Pierre Robin Syndrome
      • Mandibular hypoplasia
      • Cleft palate *
      • Eyes & ear defect
    • DiGeorge Syndrome
      • Absense of the thymus
      • Malformations of the mouth
      • Nasal clefts
      • Glossoptosis*
        • tongue displaced downwards
      • Cardiac abnormalities

image

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– The rest read from printed notes.

Formation of tongue
http://embryology.med.unsw.edu.au/Notes/head6.htm

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Terri is obsessed with making medical school as painless as possible. She studies and compiles medical school notes in a concise, easy-to-understand format. She also enjoys reading contributions by others. She is an investor in sustainability projects. Her ideal weekend is wine tasting and experimenting on bread-making. She has yet to master the art of Sourdough baking.

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