Transcript Vision Parts of the Eye 1. The Sclera 2. The Cornea 3. Conjunctiva 4.

Vision
Parts of the Eye
1. The Sclera
2. The Cornea
3. Conjunctiva
4. The Choroid Coat
5. The Ciliary Body
6. The Iris
7. The Pupil
8. The Retina
9. The Macula lutea
10. Fovea
11. The Optic Nerve
12. The Optic Disk
13. The Vitreous Humor
14. The Aqueous Humor
The Conjunctiva
• lines the inside of the eyelids and covers
the sclera (white part of the eye). It is
composed of rare stratified columnar
epithelium.
The Sclera
• White portion of the eye
• Makes up 5/6 of posterior outer
tunic
• Opaque b/c of how the collagen
and elastic fibers are arranged.
• Protects the eye
• Attachment for extrinsic muscles
The Cornea
• Window of the eye
• Helps focus entering light rays
• Composed of connective tissue w/
thin layer of epithelium
• Has many nerve fibers that enter
the margin and radiate toward the
center – associate with many pain
receptors w/ low threshold
• Cold receptors abundant
The Optic Nerve
The Choroid Coat
• Located in the back of the eye
• Attached to the retina
• Transmits images from the retina
to the brain
• Flips the pictures
• Part of the middle tunic
• Posterior 5/6 of the globe of the
eye
• Has blood vessels that nourish
surrounding parts
• Contains melanocytes
• Melanin from melanocytes absorb
excess light and keep the inside
part of the eye dark
The Ciliary Body
• Thickest part of the middle tunic
• Extends to the front from the
choroid coat
• Forms internal ring around the
eye
• Contain folds called ciliary
processes
• 2 groups of muscle fibers – ciliary
muscles
The Iris
• Controls how much light enters
the eye
• Thin diaphragm composed of
connective tissue & thin
connective tissue
• It is the colored portion of the eye
• Extends from the front of the
periphery in the ciliary body to
the middle of the cornea and the
lens
• Divides the anterior cavity
(cornea & iris) into anterior
chamber (iris and vitreous humor)
The Pupil
• The circular opening in the center
of the iris
• Black spot in the center of the iris
• Controls how much light enters
the retina
• Its diameters is usually 3-7 mm
The Lens
• Transparent
• Held in position by fibers called
suspensory ligaments (zonular
fibers) from the ciliary processes
• Lacks blood vessels
• Located behind the iris and the
pupil
• Composed of special epithelial
cells
Vitreous Humor
• Jelly- like fluid
• Fills the central core of the eye
• Helps maintain spherical shape to
the eye
• this with collagenous fibers form
the vitreous body
Aqueous Humor
• Front of iris and pupil
• Watery fluid created by
epithelium on inner surface of
ciliary body
• Separated into anterior and
posterior chambers
• Maintains eye pressure
• Nourishes front part of the eye
The Macula Lutea
The Fovea Centralis
• Yellowish spot in the retina
• The central focusing spot
• Responsible for seeing details
(reading) and color vision
• A depression in the macula lutea
• In the region of the retina that
produces the sharpest vision
• Has no rods – only cones
The Optic Disk
• Lacks receptors, often called the
blind spot
• The nerve fibers from the retina
and became part of the optic
nerve.
• A central artery and vein pass
through here
• These vessels with vessels in the
choroid coat supply blood to the
cells of the inner tunic
• Jelly- like fluid
• Fills the central core of the eye
• Helps maintain spherical shape to
the eye
• this with collagenous fibers form
the vitreous body
The Retina
• Complex structure
– Layers of (epithelium, nerve fibers, & membranes)
• Contains photoreceptors called rods and cones
• Continuous with the optic nerve and extends to the front as the inner lining of
the eyeball
• 6 retinal cell groups: rods, cones, bipolar neurons, ganglion cells, horizontal cells
and amacrine cells.
• provide direct path for impulses to the receptors to the optic nerve & brain
The retina contains two types of photoreceptors, rods and cones.
•The rods are more numerous, some 120 million, and are
more sensitive than the cones.
•However, they are not sensitive to color. The 6 to 7 million
cones provide the eye's color sensitivity and they are much
more concentrated in the central yellow spot known as the
macula.
•In the center of that region is the " fovea centralis ", a 0.3 mm
diameter rod-free area with very thin, densely packed cones.
The receptors in the retina
Pigment epithelium
• the pigmented cell layer just outside the
neurosensory retina
• nourishes retinal visual cells
• firmly attached to the underlying choroid
and overlying retinal visual cells.
Rods
Cones
• Responsible for black
and white vision
• The rods are more
numerous and more
sensitive than the
cones
• they are absent in the
fovea centralis
• Responsible for
color vision
• Densely packed in
the fovea centralis
Horizontal cells
Bipolar cells
• Bipolar cells exist
• Horizontal cells
between rods and
integrate and
cones and ganglion
regulate the input
cells.
from rods and cones.
• They transmit
• They are also
signals from the
responsible for
rods and cones to
allowing eyes to
the ganglion cells.
adjust to see well
under both bright
and dim light
conditions.
Amacrine cell
Ganglion cell
• Amacrine cells are
interneurons in the
retina.
• They are
responsible for
70% of input to
retinal ganglion
cells.
• They lack axons –
but have many
dendrites
• A Ganglion cell is a
type of neuron located
near the inner surface
of the retina
• It receives visual
information from rods
and cones via two
intermediate neuron
types: bipolar cells
and amacrine cells.
• It transmits visual info
to thalamus,
hypothalamus and
midbrain.
Direction of Impulse
1. Photons move through the 6 layers of cells
and strike the rods and cones
2. They process the light information
3. This info is integrated by the horizontal cells
4. The info travels to the bipolar cells
5. This info then travels to the amacrine cells
6. The impulses (info) finally converge at the
ganglion cells
7. The axons of the ganglion cells carry the
info to the brain
Optic Nerve
(Cranial nerve 2)
• The optic nerve, also known as cranial
nerve 2, transmits visual information from
the retina to the brain
• It is composed of the axons of the retinal
ganglion cells
• The ganglion cell axons are myelinated by
oligodendrocytes – since it is part of the
CNS
THE END