Tuesday, March 17, 2015
Structure of eye
The eye is a very complex organ that sends a huge amount of information to the brain. It has a very specific design to capture and analyze light. In its simplest description, the eye is a box, with a lens to focus the light that enters it, and cells to process the light.It is a window to our emotions, and some say, to the soul. Explore the complexities of the human eye.
fig. Structural of human eye.
Optic nerve :
This carries the impulses generated by the retina to the brain to be turned into images in the brain.
This is a membrane layer in the inside of the eye that contains rod cells (lets you see in the dark
because they are sensitive to low light intensities) and cone cells (lets you see in bright light because its
works best at higher light intensities).
It converts the light into electric impulses to be sent to the brain via the optic nerve. This conversion is
called photoelectric conversion.
pupil : The pupil is actually the gap created by the iris.
The pupil either dilates or contracts with the help of the iris.
This controls the amount of light entering the eye so that the retina and lens doesnt get damaged.
In bright light the pupil becomes small by relaxing the muscles in the iris in dim light it dilates (becomes
big) by contracting the muscles in the iris.
Iris : This is the muscle surrounding the pupil gap.This helps in dilating and making the pupil smaller.
Its made up of radial and radial muscles (antagonistic pairs).The longitudinal muscles contract and the
radial muscles relax to make the pupil big. The vise verse happens to make the pupil smaller.
cornea :This is the transparent layer of the sclera, which is also thinner than the sclera, that covers the front
part of the eye (that is the iris, pupil, and anterior chamber of the eye).
It has 2 functions. Its most important functions is to help in the double refraction of light tot he retina
with the help of the lens.
The light first gets refracted by the cornea then this light travels to the lens to get refracted further
thereby bringing about vision. The other function is for it to act as a protection layer.
lens : This is an transparent organ in the inner eye that is filled with a liquid. It helps the refraction of light,
with the help of the cornea, onto the retina.
The lens helps in seeing far and near objects be contracting and relaxing with the help of the ciliary
bodies (muscles) that are connected to them.
The ciliary muscles contract to make the lens thin and help see distance objects by refracting the light
accordingly on the retina.
The ciliary bodies relax to make the lens fatten up to see near objects by refracting the light
accordingly on the retina.
When this method of lens contraction and relaxation malfunctions you get either short sightedness or
near sightedness.
Ciliary body :
Part of the eye between the iris and the choroid.
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