The Anatomy of The Eye
The anatomy and physiology of the human eye is an important part
of many courses (e.g. in biology, human biology, physics, and
practical courses in medicine, nursing, and therapies.
This page is a very basic introduction the subjects of "The Eye"
and "Visual Optics" more generally.
It
includes a simple diagram of
the eye together with definitions of
the parts
of the
eye
labelled
in the
illustration.
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Above: Schematic diagram of the Structure of the
Human Eye.
|
Term
|
Definition / Description
|
|
|
Aqueous Humour
|
The aqueous humour is a jelly-like
substance located in the anterior chamber
of the eye.
... more about the Aqueous Humour |
|
Choroid
|
The choroid layer is located behind the retina and
absorbs unused radiation. ... more about
the Choroid |
|
Ciliary Muscle
|
The ciliary muscle is a ring-shaped
muscle attached to the iris.
It is important because contraction and relaxation of
the ciliary muscle controls the shape of the lens. ...
more about the Ciliary Muscle |
|
Cornea
|
The cornea is a strong clear bulge located at the
front of the eye (where it replaces the sclera - that
forms the outside surface of the rest of the eye).
The front
surface of the adult cornea has a radius of approximately
8mm.
The cornea contributes to the image-forming process by
refracting light entering the eye.
... more
about the Cornea |
|
Fovea
|
The fovea is a small depression (approx. 1.5 mm
in diameter) in the retina.
This is the part of the retina in which high-resolution
vision of fine detail is possible. ...
more about the Fovea |
| Hyaloid |
The hyaloid diaphragm divides the aqueous
humour from the vitreous humour.
...
more about the Hyaloid Membrane |
|
Iris
|
The iris is a diaphragm of variable
size whose function is to adjust the size of the pupil
to regulate the amount of light admitted into the eye.
The iris is the coloured part of the eye (illustrated in
blue above but in nature may be any of many shades of blue,
green, brown, hazel, or grey). ... more about the Iris |
|
Lens
|
The lens of the eye is a flexible unit
that consists of layers of tissue enclosed in a tough
capsule. It is suspended from the ciliary muscles by
the zonule fibers. ... more about the Lens |
|
Optic Nerve
|
The optic nerve is the second cranial nerve and
is responsible for vision.
Each nerve contains approx. one million fibres transmitting
information from the rod and cone cells of the retina. ... more about the Optic Nerve |
|
Papilla
|
The papilla is also known as the "blind spot" and
is located at the position from which the optic nerve leaves
the retina. ... more about the Optic Papilla |
|
Pupil
|
The pupil is the aperture through which light -
and hence the images we "see" and "perceive" -
enters the eye. This is formed by the iris. As the
size of
the iris increases (or decreases) the size of the pupil
decreases (or increases) correspondingly. ... more
about the Pupil
|
|
Retina
|
The retina may be described as the "screen"
on which an image is formed by light that has
passed into the eye via the cornea, aqueous humour, pupil,
lens, then the hyaloid and finally the vitreous humour
before reaching the retina.
The retina contains photosensitive elements (called
rods and cones)
that convert the light they detect into nerve impulses
that are then sent onto the brain
along the optic nerve. ...
more about the Retina |
|
Sclera
|
The sclera is a tough white sheath around
the outside of the eye-ball.
This is the part of the eye that is referred to by
the colloquial terms "white of the eye".
... more about the Sclera |
|
Visual Axis
|
A simple definition of the "visual axis"
is "a straight line that passes through both the centre
of the pupil and the centre of the fovea".
However,
there is also a stricter definition (in terms of nodal
points) which is important for specialists in optics
and related subjects. ... more about the Visual Axis |
|
Vitreous Humour
|
The vitreous humour (also known as the "vitreous
body") is a jelly-like substance.
... more about
the Vitreous Humour |
|
Zonules
|
The zonules (or "zonule fibers")
attach the lens to the ciliary muscles. ... more about
the Zonules |
|
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Knowledge of aspects of the human nervous system and familarisation
with the key terms associated with it is an essential part of the
syllabus for many exams - including GCSE Biology, "A"-Level
Biology and Human Biology, and training in therapies such as Massage,
Aromatherapy, Accupuncture, Reiki, and many others.
... End of Article ...
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