From what tissue does the retina develop?

The retina develops from neuroectoderm: the optic vesicle, an outgrowth of the forebrain, invaginates into the optic cup whose inner layer forms the neural retina and outer layer the retinal pigment epithelium.

Where does the inner ear come from?

The inner ear arises from the otic placode, a thickening of surface ectoderm beside the hindbrain that invaginates into the otic vesicle and then differentiates into the cochlear and vestibular parts of the membranous labyrinth.

Eye and Ear Development

The eye and the ear, the principal special sense organs, form from the interaction of several embryonic tissue layers. The eye begins as an outgrowth of the developing forebrain (the optic vesicle) that induces an overlying lens placode, while the inner ear arises from a thickening of surface ectoderm called the otic placode. This topic covers the embryonic origins and morphogenesis of the eye and the ear.

Definition

Eye and ear development is the morphogenesis of the visual and auditory-vestibular sense organs—the eye from forebrain-derived optic neuroectoderm together with a lens placode, and the inner ear from an otic placode of surface ectoderm—through inductive tissue interactions, invagination and progressive differentiation.

Scope

The entry covers the neuroectodermal origin of the retina and optic structures, the surface-ectoderm origin of the lens via placode induction, the formation of the inner ear from the otic placode and its differentiation into cochlear and vestibular apparatus, and the contributions of surrounding mesenchyme and neural crest. It is a developmental reference within embryology and does not provide clinical management instructions.

Key concepts

Optic vesicle and optic cup
Lens placode and induction
Neuroectodermal origin of the retina
Retinal cell-fate determination
Otic placode and otic vesicle (otocyst)
Cochlear and vestibular differentiation
Placode induction by surrounding tissues

Mechanisms

The eye originates as the optic vesicle, an evagination of the forebrain neuroectoderm, which contacts the surface ectoderm and induces it to form the lens placode; the vesicle then invaginates into a double-walled optic cup whose inner layer becomes the neural retina and outer layer the retinal pigment epithelium, while the lens placode pinches off to form the lens (Graw, 2003; Moore et al., 2020). Within the retina, multipotent progenitors give rise to the several neuronal and glial cell types in a regulated order (Bassett & Wallace, 2012). The inner ear arises independently as the otic placode, a thickening of surface ectoderm next to the hindbrain that is induced by signals from adjacent tissues; the placode invaginates to form the otic vesicle (otocyst), which elaborates into the cochlear duct and the vestibular labyrinth (Sai & Ladher, 2015; Sadler, 2018).

Clinical relevance

The dependence of eye and ear formation on precisely timed inductive interactions underlies the developmental basis of many congenital sensory anomalies, and the genetic networks involved are reviewed in the context of congenital eye defects (Graw, 2003). This entry describes that developmental anatomy for reference and is not a basis for individual diagnostic or treatment decisions.

History

The inductive origin of the lens from the optic vesicle is a classic example in experimental embryology, and the placodal origins of the eye and ear are codified in standard texts (Moore et al., 2020; Sadler, 2018). Molecular developmental biology has since detailed the gene networks of eye formation and congenital eye defects (Graw, 2003), the progenitor logic of retinal cell-fate determination (Bassett & Wallace, 2012), and the induction and morphogenesis of the otic placode (Sai & Ladher, 2015).

Key figures

Jochen Graw
Valerie Wallace
Raj Ladher

Seminal works

graw-2003
sai-ladher-2015
bassett-wallace-2012

Frequently asked questions

From what tissue does the retina develop?: The retina develops from neuroectoderm: the optic vesicle, an outgrowth of the forebrain, invaginates into the optic cup whose inner layer forms the neural retina and outer layer the retinal pigment epithelium.
Where does the inner ear come from?: The inner ear arises from the otic placode, a thickening of surface ectoderm beside the hindbrain that invaginates into the otic vesicle and then differentiates into the cochlear and vestibular parts of the membranous labyrinth.