Sensory - Vision Development
These notes introduce the development of the eye: induction and regional specification of the eye structures, maturation and formation of retina and optic tectum neuronal connections. The adult eye has contributions from several different embryonic layers eventually forming neuronal, supportive connective tissue, optical structures, and muscular tissues. Additional pages are being developed to cover specific issues of this anatomical structure.
|Senses Links: Introduction | placode | Hearing and Balance hearing | balance | vision | smell | taste | touch | Stage 22 | Category:Sensory|
Weeks 3-4 Eye Fields-Optic Vesicle
Weeks 5-6 Optic Cup, Lens Vesicle, Choroid Fissure, Hyaloid Artery
Weeks 7-8 Cornea, Anterior Chamber, Pupillary Membrane, Lens, Retina
Weeks 9-15 Iris, Ciliary Body
Weeks 8-10 Eyelids
The lens or crystalline lens or aquula (Latin, aquula = a little stream) has a key role in focussing light (with the cornea) upon the neural retina. The lens embryonic origin is from surface ectoderm of the sensory placodes that form in the head region (More? Week 4 - Placodes). The lens focusses by refracting light as it passes through the biconvex lens, which can be altered in shape (accommodation) by surrounding ciliary muscles. These ciliary muscles are activated (contracted) by parasympathetic innervation from the ciliary ganglion itself innervated by the oculomotor nerve (Cranial Nerve III) (More? Cranial Nerves).
surface ectoderm -> lens placode -> lens pit -> lens vesicle -> lens fibres -> lens capsule and embryonic/fetal nucleus.
This neuroscience term describes how the developing retina is precisely "mapped" onto the visual cortex through a series of signaling and activity dependent mechanisms. This follows from Hubel and Wiesel (1981 Nobel Prize in Physiology or Medicine) key discoveries (1959-70) of how in development system matching occurs in the visual system. The topographic map establishes an ordered neuronal connection between sensory structures and the central nervous system.
The retinotectal map (eye to brain) of birds (lower vertebrates):
- temporal (posterior) retina is connected to the rostral (anterior) part of the contralateral optic tectum
- nasal (anterior) retina to the caudal (posterior) tectum
- ventral retina to the dorsal (medial) tectum
- dorsal ventral (lateral) tectum
Retinal waves a form of coordinated spontaneous activity that occurs in the developing retina. These waves of electrical activity (action potentials) are thought to have a role in establishing the initial retinotopic map by correlating/coordinating the activity of neighbouring retinal ganglion cells.
EphA/ephrin-A molecular signaling also thought to have a role in establishing the initial retinotopic map.
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Bookshelf vision development
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- retina - The stratified sensory structure of the eye, formed from the neural ectoderm that extends from the forebrain (diencephalon) to form initially the folded optic cup. Vertebrates have ten identifiable layers formed from nerve fibers, neurons, membranes, photoreceptors and pigmented cells. Light must pass through nearly all these layers to the photoreceptors. (1. Inner limiting membrane - Müller cell footplates; 2. Nerve fiber layer; 3. Ganglion cell layer - layer of retinal ganglion cells their axons form the nerve fiber layer and eventually the optic nerve; 4. Inner plexiform layer - another layer of neuronal processes; 5. Inner nuclear layer; 6. Outer plexiform layer; 7. Outer nuclear layer; 8. External limiting membrane - layer separating inner segment portions of photoreceptors from their cell nuclei; 9. Photoreceptor layer - rods and cones that convert light into signals; 10. Retinal pigment epithelium).
- retinal pigment epithelium - (RPE) An epethial pigmented cell layer lying outside the sensory retina, formed from the outer layer of the folded optic cup. The RPE is firmly attached to the underlying choroid and overlying retinal visual cells, for which it has a nutritional role.
- retinal waves - A form of coordinated spontaneous activity that occurs in the developing retina. These waves of electrical activity (action potentials) along with EphA/ephrin-A signaling are thought to have a role in establishing the initial retinotopic map by correlating/coordinating the activity of neighbouring retinal ganglion cells.
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Cite this page: Hill, M.A. (2020, July 9) Embryology Sensory - Vision Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Sensory_-_Vision_Development
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G