Development of eyes and ears

Eyes

Image result for development of eye

 

(I) Retina and optic nerve

  • Optic vesicle of prosencephalon extends laterally
  • Contacts surface ectoderm
  • Optic vesicle invaginated to form optic cup:
  1. Outer layer – forms pigmented layer of retina
  2. Inner layer anterior 1/5 – iris and ciliary body
  3. Inner layer posterior 4/5 – All layers of retina except pigmented layer
  • Mouth of optic cup forms pupil
  • Optic stalk invaginated by central artery of retina – gets enclosed in optic stalk – forms optic nerve

 

(II) Lens

  • Surface ectoderm thickens – forms lens placode
  • Lens placode invaginated at optic cup mouth – forms lens vesicle
  • Lens vesicle separates from surface ectoderm
  • Lies in optic cup mouth
  • Cells of posterior layer of lens vesicle elongate – forms lens fibers

 

(III) Choroid and sclera – Forms from mesenchyme around optic vesicle


 

Ear

Develops from pharyngeal arches (link)

Muscles of middle ear – tensor tympani (1st arch) and stapedius muscle (2nd arch)

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