DEVELOPMENT OF THE HEAD AND NECK

Innovations in the early evolution of vertebrates

Phylogeny of early deuterostomes

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PLACODES
Localized thickened areas of specialized ectoderm, lateral to the neural crest, at the border between neural plate and the future epidermis.

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Different kinds of placodes

Distribution of placodes at 3 developmental stages

Development of placodes: similarities

Development of placodes - differences

Location of placodes

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Location of placodes

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Location of placodes

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Branchiomeric nerves: origins and axon projection patterns

Fates of placodes

Development of organs of special sense

Olfactory epithelium: development of the nose

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Olfactory placode gives rise to:

Development of the eye :
1. evagination of forebrain (optic vesicle)
2. invagination of lens placode

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Development of inner ear

Otic placode invagination:
otic pit

Otic pit to otic vesicle

Differential growth of otic vesicle

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Otic capsule: future petrous part of temporal bone