Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
124 Cards in this Set
- Front
- Back
|
4 structures that light has to pass through to get to the retina:
|
1. Cornea
2. Anterior chamber 3. Lens 4. Vitreous humor |
|
|
5 Layers of the Cornea:
|
1. Epithelium
2. Bowman's membrane 3. Stroma 4. Descemet's membrane 5. Endothelium |
|
|
What type of epithelium is on the cornea? Endothelium?
|
Epithelium = Stratified squamous
Endothelium = simple cuboidal |
|
|
What are Bowman's and Descemet's membranes?
|
ECM - extracellular matrix
|
|
|
What is the Stroma made of?
|
Matrix + Stromal fibroblasts
|
|
|
How is the Stroma arranged?
|
In orthagonal layers - 90 degrees to each other.
|
|
|
What maintains the spacing within the stroma?
|
Hydration
|
|
|
If you're going to injure a layer of the cornea which would it be and why?
|
The epithelial layer - it heals very easily; anything penetrating beneath it heals very slowly and creates an opaque scar.
|
|
|
Function of the cornea:
|
it is the major refractive structure of the eye - not the lens!
|
|
|
2 things that contribute to the transparency of the cornea:
|
1. The alignment and hydration of its components
2. The fact that it is avascular |
|
|
Structure that is important for maintaining the hydration of the corneal stroma:
|
Endothelium - it has pumps
|
|
|
Refractive index of the cornea:
|
1.38
|
|
|
How does the cornea function as a refractive structure?
|
By virtue of its curvature and refractive index.
|
|
|
What is the Corneal Stroma?
|
The thick connective tissue layer that contains few cells and lots of ECM
|
|
|
What does the ECM in the cornea stroma consist of?
|
-Type I collagen
-Proteoglycans |
|
|
Arrangement of collagen fibrils in the stroma:
|
Perpendicular - orthogonal strata --> layers oriented 90 degrees to each other
|
|
|
Why is the organization and spacing within the stroma important?
|
Because it allows for light to pass through unimpeded.
|
|
|
What maintains the spacing and organization of the stroma?
|
Hydration
|
|
|
And the spacing is again, necessary for:
|
Transparency
|
|
|
What alters the organization and transparency of the stroma? What is the result?
|
Swelling - cornea becomes opaque
|
|
|
Business end of the cornea:
|
Endothelium
|
|
|
Function of endothelium
|
Continuously pumps water out of adjacent stroma
|
|
|
Importance of endothelium
|
Maintains proper corneal hydration and thus transparency
|
|
|
What direction does the endothelium pump water in?
|
Anterio chamber -> stroma -> out of stroma
|
|
|
Why is it bad of the endothelium gets damaged?
|
B/c it can't undergo mitosis; if damaged, that's it.
|
|
|
What is it called when too much endothelium gets damaged?
|
Corneal decompensation
|
|
|
What is the treatment for a damaged corneal endothelium?
|
Corneal transplant
|
|
|
How can the curvature of the cornea be changed?
|
Via LASIK
|
|
|
Possible side effect of LASIK:
|
Corneal decompensation
|
|
|
2 major causes of loss of corneal transparency:
|
1. Damage to endothelium
2. Damage to stroma |
|
|
Anterior chamber contains what:
|
Aqueous humor
|
|
|
Composition of aqueous humor is similar to
|
CSF
|
|
|
Direction of aqueous humor flow:
(6 steps) |
1. Ciliary processes (productn)
2. Posterior chamber 3. Anterior chamber 4. Trabecular meshwork 5. Schlemm's canal 6. Veins of Sclera |
|
|
Functions of the aqueous humor:
|
Nutritive?
|
|
|
Where is Aqueous humor produced?
|
By the epithelium of the ciliary body.
|
|
|
Main component of aqueous humor:
|
Water
|
|
|
Why is the aqueous humor important?
|
Its secretion and outflow determine intraocular pressure
|
|
|
What is associated with increased intraocular pressure?
|
Glaucoma
|
|
|
What 2 factors allow the aqueous humor to be transparent?
|
1. Avascular
2. Mostly water |
|
|
3 Structural components of the lens:
|
1. Capsule
2. Epithelium 3. Lens fibers |
|
|
What is the lens capsule?
|
The ECM surrounding the lens
|
|
|
What is the lens epithelium cell type? Where is it?
|
Simple cuboidal - on anterior surface of the lens.
|
|
|
What are the lens fibers?
|
The cells that make up the body of the lens.
|
|
|
What is the function of the lens?
|
Refraction - but second to the cornea in refractive power.
|
|
|
What supports the lens?
|
Suspensory ligaments (zonules) attached to the ciliary body.
|
|
|
What is it called when the lens changes shape to focus on near objects?
|
Accommodation
|
|
|
What has the lens been called?
|
The undead - it loses all its organelles but somehow manages to stay alive!
|
|
|
3 Factors that make the Lens transparent:
|
1. Low protein concentration and no organelles
2. Little ECM 3. It's avascular |
|
|
What proteins ARE in the lens, though in low concentration?
|
Crystallins
|
|
|
What are Zonules of Zin?
|
Aka Zonular fibrils - the zonules; suspensory ligaments. All one and the same.
|
|
|
What muscle is responsible for accomadation? What nervous input?
|
Ciliary muscle - PNS
|
|
|
What is the definition of a Cataract?
|
Opacity of the lens
|
|
|
3 Causes of Cataracts:
|
-age
-surgery -diet |
|
|
What is the problem that results in cataracts?
|
Thick lens crystallins
|
|
|
What is Presbyopia?
|
Aka Short Arm Disease - when the lens elasticity has declined and patients can't focus on near objects.
|
|
|
Vascular structures of the eye; collectively called what?
|
Ciliary body + Choroid
= Uvea |
|
|
3 Important Functions of the Ciliary Body:
|
1. Muscles control lens shape
2. Produces aqueous humor 3. Zonules support the lens |
|
|
The iris is composed of what?
|
-Connective tissue + melanocytes
-Dilator and sphincter muscles |
|
|
Functions of the iris:
|
Constriction and Dilation for controlling the size of the pupil.
|
|
|
6 things to note about the Vitreous body (humor):
|
MAMA ten
1. Mostly water 2. Avascular 3. Mostly acellular 4. Transparent 5. ECM is Type 2 collagen + hyaluronic acid 6. Nutritive |
|
|
3 things that make the vitreous body transparent:
|
1. 99% water
2. Structural components dispersed and in lo conc. 3. Avascular |
|
|
Where is the highest density of collagen fibrils in the vitreous cortex?
|
Adjacent to the retina
|
|
|
What separates the vitreous body and retina?
|
Inner limiting lamina
|
|
|
What is the Inner Limiting Lamina, and what is it composed of?
|
A basement membrane; made up of retinal Muller glial cells
|
|
|
What happens if the posterior vitreous becomes detached?
|
It can tear and put a hole in the retina.
|
|
|
2 Main regions of the retina derived from different layers of the optic cup during embryogenesis:
|
1. Neural/sensory retina
2. REtinal pigment epithelium |
|
|
How many layers are in each region of the retina?
|
Neural - 9
RPE - 1 |
|
|
What are the layers of the retina?
|
1. RPE
2. Outer segments of rods/cones 3. Inner segments of rods/cones 4. outer nuclear layer 5. Outer plexiform layer 6. Inner nuclear layer 7. Inner plexiform layer 8. Ganglion cell layer 9. Nerve fiber layer |
|
|
What layer is just internal to the nerve fiber layer where the optic nerve converges?
|
The inner limiting lamina made up of Muller's glial cells
|
|
|
What happens in plexiform layers?
|
Synapses of axons with the next layer of cells.
|
|
|
What synapse occurs in the outer plexiform layer?
|
Axons of rods/cones synapse on bipolar neurons
|
|
|
What happens in the inner plexiform layer?
|
Axons of bipolar neurons synapse on ganglion cells.
|
|
|
What happens to the axons of ganglion cells?
|
They converge to form the optic nerve in layer 9 - NFL
|
|
|
Where is the blind spot in the eye?
|
The point where the NFL leaves the eye as the optic nerve
|
|
|
Function of the Fovea:
|
High acuity vision - it has a high density of cone photoreceptors.
|
|
|
Where is the fovea located?
|
In the center of the macula
|
|
|
What allows the fovea to have such high acuity?
|
The displacement of other layers so that there is unimpeded light hitting the photoreceptors.
Also no blood vessels. |
|
|
What do the outer segments of photoreceptors contain?
|
Flattened membrane discs with photosensitive visual pigments like rhodopsin.
|
|
|
What do the inner segments of photoreceptors contain?
|
Organelles for protein synthesis and energy production
|
|
|
2 types of photoreceptors:
|
1. Rods
2. Cones |
|
|
Where are rods numerous?
Function? |
-Everywhere except at the fovea
-Very light-sensitive |
|
|
What are the functions of cones?
|
high acuity and color vision
|
|
|
What is between rods and cones?
|
IPM - interphotoreceptor matrix
|
|
|
Function of the IPM
|
Keeps the retina attached to the back of the eye.
|
|
|
The optic nerve is made of:
|
Ganglion cell axons
|
|
|
What interactions occur within the retina to allow partial processing of info before its sent to the brain?
|
Interactions of Horizontal and Amacrine neurons
|
|
|
What are the major glial cells of the retina?
|
Muller glial cells
|
|
|
Where are muller glial cells in the retina?
|
Spanning the entire retina from the vitreous interface to the photoreceptor layer!
|
|
|
Where does the optic nerve go after exiting the eyeball?
|
To the lateral geniculate body to the visual cortex of the occipital lobe.
|
|
|
What happens if the retina is damaged?
|
Muller glial cells proliferate and migrate to produce scarring.
|
|
|
RPE is made of what type of cells?
|
Simple cuboidal
|
|
|
What is within RPE cells?
|
Melanin pigment
|
|
|
What separates the RPE layer from the choroid?
|
Bruch's membrane
|
|
|
What is the RPE situated between?
|
Choroid (externally)
Bruch's membrane (externally) ---RPE---- Retina (internally) |
|
|
What is housed within the choroid?
|
Capillary bed
|
|
|
4 Major functions of the RPE:
|
1. Absorbs stray light
2. Vitamin A metabolism 3. Phagocytizes shed photoreceptor outer segments 4. Provides the outer blood-retinal barrier |
|
|
What is the result of damage to the RPE, and why?
|
Photoreceptors will die because all nutrients to the retina must pass first through the RPE
|
|
|
What is the Choroid?
|
The vascular bed located adjacent to the RPE
|
|
|
Function of the Choroid:
|
Provides nutrients to the outer retina
|
|
|
Why does the choroid have to supply nutrients to the outer retina?
|
Because only the inner retina has capillaries.
|
|
|
Uvea is composed of:
|
Choroid + Ciliary body
|
|
|
What surrounds the uvea?
|
The sclera
|
|
|
another name for the Uvea:
|
Vascular tunic
|
|
|
What is the sclera structure like?
|
Dense fibrous tunic
|
|
|
What is the sclera continuous with?
|
The corneal stroma
|
|
|
functions of the Sclera (2):
|
1. Tough protective cover of the globe
2. Insertion of extraocular muscles |
|
|
What is the ciliary body?
|
The anterior extension of the choroid
|
|
|
Functions of ciliary body:
|
1. Muscular control of accommodation
2. Produces aqueous humor 3. Supports the lens via zonules |
|
|
What covers the ciliary body?
|
A bilayered epithelium; one layer is pigmented, one is not.
|
|
|
What is the iris composed of?
|
Connective tissue stroma with melanocytes
|
|
|
What covers the iris?
|
Pigmented epithelium on the posterior surface
|
|
|
What important structures are contained within the iris?
|
-Dilator pupillae muscle
-Sphincter pupillae muscle |
|
|
Function of iris muscles:
|
Controls the amt of light entering the pupil
|
|
|
What determines eye color?
|
The # and type of melanocytes in the iris
|
|
|
Hole in middle of iris:
|
pupil
|
|
|
Primary source of blood to the eye:
|
ICA --> Ophthalmic artery
|
|
|
2 branching systems from ophthalmic artery:
|
1. Retinal artery system
2. Ciliary artery system |
|
|
Fate of the retinal artery system:
|
-Becomes central artery of the retina
-Supplies the inner retinal layers and anterior retina. |
|
|
2 branches of the ciliary artery system:
|
1. Anterior ciliary artery
2. Posterior ciliary artery |
|
|
What structure only recieves blood from the anterior ciliary artery?
|
Cornea
|
|
|
What 2 structures recieve blood from both the anterior and posterior ciliary arteries?
|
-Ciliary body
-Iris |
|
|
Branches of the posterior ciliary artery:
|
-Long posterior ciliary artery
-Short posterior ciliary artery |
|
|
What does the short post ciliary artery supply?
|
Choroid and the outer retina
|
|
|
What does the long posterior ciliary artery supply?
|
-Ciliary body
-Iris |
