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38 Cards in this Set

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All information from the photoreceptors in the retina is conducted by the ___________ to the brain.
optic nerve
Define accomodation.
altering the shape of our lens so we are able to focus light as we look at varying distances
What muscles are used for accomodation?
Ciliary muscles within the ciliary body which are connected to the lens by suspensory ligaments
What is the function of the iris?
Gives eye color; adjusts the amount of light entering the body
What is the function of the fovea centralis?
used for fine vision
What is found at the center of the fovea?
Macula - it is weak and it degenerates easily -- called macular degeneration
What is the eye from embryologically?
the brain
Describe the formation of the retina.
1. The eye begins from part of the brain.

2. It invaginates and grows toward the surface ectoderm and forms a cup from neural tissue.

3. Differentiates into a pigmented layer and neural layer.

4. The 2 layers will contact either other causing the liquid space in between to disappear.
Describe the formation of the lens.
The surface ectoderm starts to invaginate which gives rise to the lens. THE LENS IS OF ECTODERMAL ORIGIN.

As it grows, it will become completely separated from the ectoderm.

Later in development we have the growth of the vessels called the HYALOID vessels into the eye all the way to the lens.
What do the cornea and sclera develop from?
Connective tissue under the epithelium.
What does the neural layer give rise to?
retina
What does the pigmented layer give rise to?
Retinal Pigmented Epithelium (RPE)
Why can you have retinal detachment?
The neural retins (retina) and the pigmented layer (retinal pigmented epithelium) fuse. This association; however, is relatively weak.
How long does it take the eye to develop?
After 2 months the eye is pretty much developed.
The _____________ is very rich in blood vessels and is heavily pigmented.
choroid.
The cells of the lens are differentiating into ______________ .
Primary lens fibers. The other cells will die leaving us the primary lens which we will have throughout life.
(T/F) The lens continues to grow throughout life.
True
Which structures in the eye are avascular?
retina (has a little vasculatization), lens, vitreous, and the cornea

if there is too much vascularization, it will affect vision.
(T/F) Because the eye develops so fast, the vitreous caivty has to be vascularized to support this, but those vessels must later be removed.
True
What are the 3 layers of the eye?
1. outer -- cornea, sclera, limbus.

2. choroid

3. retinal layer - nervous tissue (from nervous ectoderm)
What is the limbus?
transition region between cornea out in front and sclera in the back and towards the side
What is the choroid?
Contains the blood vessels and also have the ciliary body as an extension of it.
Where does the iris come from?
LAter in development, the iris comes from the choroid.
What is the ora serrata?
The retinal layer does not go all the way up to the ciliary body. There is a gap between called the ora serrata. This is where surgeons can enter without touching the retina.
Describe the cornea.
It must allow passage of light. Covered with epithelium which rests on the basal lamina and a very thick basement membrane called Bowman's layer.

The stroma contains very dense collagen.

Descement's layer - another BM like structure

The cornea is not vascularized -- it suppresses the growth of blood vessels
Which structure is more highly organized: cornea or sclera?
cornea - highly organized collagen fibers.

sclera - much more random collagen fibers.
Does the cornea have nerves?
Yes, it has nerves that go into the epithelium. It is very painful if you scratch.
What is being done in the Lasik procedure?
Use of a laser to reshape the cornea.
What holds the lens in place?
filaments/suspensory ligaments hold the lens in place. They contain fibrillin.

Have lens dislocation in Marfan syndrome because fibrillin is the location of the mutation.
What is the sequence of events so you can see objects that are close?
1. ciliary muscle contracts
2. tension is reduced.
3. lens rounds to see close objects.
What is the sequence of events so we can see objects that are far?
1. Ciliary muscle is relaxed.
2. tension increases.
3. lens flattens so we can see things far away.
There is movement of liquid in the eye. Where is this liquid made and what tract does it follow during its flow.
The liquid is made by the ciliary body. It travels between the lens and the iris and comes into the anterior chamber. It leaves the eye by going through a filter called the trebecular meshwork via the Canal of Schlemm into the aqueous veins.
What happens in the trabecular meshwork of the Canal of Schlemm gets blocked?
Glaucoma and this pressure can also damage the function of the optic nerve.
What are the epithelium layers of the ciliary boddy. Where does secretion of the liquid originate?
2 layers:
1. Outer non-pigmented
2. inner pigmented

Secretion occurs from the non-pigmented layer
What is the iris?
Part of the iris is heavily pigmented and the epithelium that is continuous with the epithelium ciliary body is full of pigmented granules.
What determines the size of the pupil?
The dilator muscle runs under the pigmented layer and then below that is the constrictor muscles. These determine the size of the pupil.
Describe the development of the lens in regards to the lens fiber cells.
The lens is of epithelium origin and has no blood vessels. It is a single layer of epithelium cells that elongate to give the lens fiber cells. The cells in teh center will die during development during development leaving just the outer elongated cells.
Contains specific proteins called CRYSTALLINS
Describe the ADULT lens.
Single layer of simple cuboidal epithelium and there is a BM on the outer surface called the lens capsule (very tough)

In the inner lens which are now just remnants of the lens fibers. These fibers are full of the protein crystallin.

There are no blood vessels and no CT except for the BM containing type 4 and laminin.