2012 Group Project 1

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Vision Development

--Mark Hill 12:20, 15 August 2012 (EST) This is a better title.

Introduction

Eyes are an important sensory organ shared across many different species and allow organisms to gather useful visual information from their environment. The visual system uses light from the environment and processes this information in the brain for visual perception. The visual system is complex, and is made up of various structures that work together to form vision. Each of the structures in the eye have specific tasks which contribute to the visual system.

The main anatomical structures of the eye are as follows:

-Cornea

-Sclera

-Iris

-Ciliary body

-Choroid

-Retina

-Anterior chamber

-Posterior chamber

Research history

Development

The eye itself is formed from three main components; the optic placode of the head ectoderm, the optic vesicle of the mesoderm (lying under the optic placode) and the cells of the developing brain from the neural tube. The optic placode contributes the lens to the eye, the optic vesicle gives rise to the cornea and sclera, while the neural tube will produce the retina and choroid layers.[1] Cells from the neural tube will also produce the optic nerve, which receives nerve impulses from the retina of the eye. Eyes initially form as laterally paired structures and migrate medially in the human embryo. In other animals such as birds and lizards, the eyes do not migrate and develop laterally on the head. The optic placodes become prominent on the surface of the embryo at approximately Stage 14 of development.


Optic Nerve

The optic nerve consists of nerve fibres that transmit information from the retinal photoreceptor cells to the brain. The optic nerve is formed from the optic stalk. The optic stalk develops as the optic vesicle migrates from its origin in the neural tube to its destination - the surface ectoderm - where it will fuse with the optic placode (also known as the lens placode, which, as the name suggests, will contribute the lens to the eye).


Fig. 1: Early formation of the optic vesicle from the neural groove.


As can be seen in figure 1 above, the optic vesicle forms from the neural tube. However, note that the neural tube has not yet closed, and is still the neural groove at this point.


Fig. 2: The optic vesicle at a later stage, showing the optic stalk.


Retina

The retinal component of the eye is formed when the optic vesicle fuses with migrating cells from the developing brain.

A cross section showing fusion of the optic vesicle with components of the developing brain.[2]


Ciliary Body

EC

Iris

Lens

The lens has its origin from the optic placode, which develops on the ectodermic surface of the embryo and migrates both medially and inwards into the embryo. The lens allows accommodation of the eye, and adjusts its thickness in order to focus on near or far objects.

A Stage 14 embryo showing the location of an otic placode.[3]

Aqueous Chambers

Cornea

Choroid and Sclera

Eyelids

The eyelids are ectodermal in origin and are an extension of the skin which covers and protects the eye.

Lacrimal Glands

Extraocular muscles

Current research

Useful links

Glossary

Image gallery

References


External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

--Mark Hill 12:22, 15 August 2012 (EST) Please leave the content listed below the line at the bottom of your project page.


2012 Projects: Vision | Somatosensory | Taste | Olfaction | Abnormal Vision | Hearing