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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?
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:
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
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?
And the spacing is again, necessary for:
What alters the organization and transparency of the stroma? What is the result?
Swelling - cornea becomes opaque
Business end of the cornea:
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?
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
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:
Where is Aqueous humor produced?
By the epithelium of the ciliary body.
Main component of aqueous humor:
Why is the aqueous humor important?
Its secretion and outflow determine intraocular pressure
What is associated with increased intraocular pressure?
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?
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?
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:
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?
-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)
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:
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?
What 2 structures recieve blood from both the anterior and posterior ciliary arteries?
-Ciliary body
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