Exam #2: Eye Flashcards
What are the three layers of the eye?
1) Fibrous/ Corneoscleral
2) Vascular/ Uvea
3) Retina
Corneoscleral Layer of the Eye
- Most superficial part
- Cornea= anterior 1/6
- Sclera= posterior 5/6
Where does the uvea get its blood supply from?
Ophthalmic Artery
Vascular Layer of the Eye/ Uvea
Iris= anterior, eyecolor Choroid= posterior, dark heavily pigmented portion
Retinal Layer
- Neural/ innermost layer of the eye
- Anterior= thin & nonvisual
- Posterior= thin & visual
What marks the separation between the anterior & posterior portion of the retina?
Ora Serrata
What are the different chambers of the eye?
- Eye is divided into an anterior & posterior segments by the Ora Serrata
- Anterior segment is further divided into the anterior & posterior chambers by the iris
- Posterior segment contains the vitreous chamber
Contents of the Anterior Segment
- Aqueous Humor
- Iris (vascular)
- Ciliary Body & Muscle
- Lens (avascular)
- Cornea (avascular)
- Anterior Sclera
Contents of the Posterior Segment
- Vitreous Humor
- Visual Retina
- RPE
- Posterior Sclera
- Uvea
Aqueous Humor vs. Vitreous Humor
- Aqueous= anterior chamber, provides stability & nutrition to keep the avascular structures alive
- Vitreous= vitreous chamber (posterior segment), more jelly-like than aqueous humor b/c of 1% collagen)
What does dehydration of the vitreous humor lead to?
- Detached retina
- The vitreous humor helps keep the retina on the vascular layer & choroid
Cornea
- Anterior 1/6 of the eye
- Transparent
- Avascular
- Provides 2/3 of the refractive power of the eye (more than lens)
What are the five layers of the cornea from outside to inside?
1) Corneal Epithelium
2) Bowman’s Membrane
3) Corneal Stroma
4) Descemet’s Membrane
5) Corneal Endothelium
Corneal Epithelium
- Stratified squamous epithelium (non-keratinized)
- Contains microvilli (prevent drying out)
- Contains Ferritin (protects from UV damage)
- Regenerates
- Blink reflex (CN V & VII)
Bowman’s Membrane
- Anterior basement membrane
- Does not regenerate–> scarring
- Provides strength to the cornea
- Barrier to infections
- Terminates at corneoscleral limbus
Corneoscleral limbus
- Transition point of cornea & sclera
- Contains stem cell for the corneal epithelium
Corneal Stroma
- Also called the Substantia Propria
- 90% of corneal thickness
- Contains proteoglycans & type V collagen organized in 90 degree lamellae
Descemet’s Membrane
- Posterior basement membrane
- Regenerates
- Thickens with age
- Helps maintain normal curvature of the eye through pectinate ligaments
Pectinate Ligaments
Connect the sclera to the ciliary body & help maintain the normal curvature of the eye
Corneal Endothelium
- Simple squamous epithelium
- Joined by zonula adherens, zonula occludens, & desmosomes
- Adjacent to aqueous humor
- Limited proliferative ability
- Responsible for nearly all metabolic exchanges of the cornea & contains fluid pumps for hydration
Sclera
- Posterior 5/6 of the eyeball
- “White” of the eye
- Contains though fibrous connective tissue (Collagen & Elastic Fibers)
What are the three layers of the sclera?
1) Episcleral
2) Substantia Propria
3) Suprarachnoid Lamina
Episcleral Layer
- Outer layer of the sclera
- Contains tenon’s space
Tenon’s Space
A space between tenon’s capsule & periorbital fat that gives the eye room to move in
Substantia Propria
- Intermediate layer of the sclera
- Contains Tenon’s Capsule
Tenon’s Capsule
Connection to the extra-ocular muscles
Suprarachnoid Layer
- Inner layer of the sclera
- Attachment of the sclera to the choroid
- How the sclera gets nutrients
Iridocorneal Angle
Corner of the cornea & iris
Canal of Schlemm
Scleral venous sinus i.e. apparatus for outflow of aqueous humor
Contents of the Uvea
1) Iris
2) Ciliary Body
3) Choroid
Iris
- Most anterior portion of the uvea
- Color part of the eye (no pigment= pink)
Pupil
Opening between the two edges of the iris
Dilator Pupillae
- Radially arranged smooth muscle fibers that open the pupil
- SNS innervation
Sphincter Pupullae
- Circularly arranged smooth muscle fibers that close the pupil
- PNS innervation
Ciliary Body
- Anterior to the Ora Serrata
- Continuous with the iris
- Produces aqueous humor (specifically, the ciliary processes)
- Lined by two layer of simple columnar epithelium separated by a basement membrane
What are the two layers of the Ciliary Body?
1) Pigmented
2) Non-pigmented
Pigmented
- Outer layer
- Helps reduce glare
Non-pigmented
- Inner layer
- Important for transferring fluids
Ciliary Processes
- Part of the Ciliary Body
- 75 radial radial fibers that anchor to the lens
- Suspend the lens
- Produce aqueous humor
- Contains tight junctions that create a blood-aqueous barrier
Floater
When blood passes the blood-aqueous barrier established by the ciliary processes
Describe the flow of aqueous humor.
1) Ciliary process
2) Behind the iris
3) Out the pupil
4) Toward iridocorneal angle
5) Canal of Schlemm
6) Diffusion into venous network
Open Angle Glaucoma
- Disruption of the Canal of Schlemm (aqueous humor outflow)
- Gradual increase in symptoms/ intraocular pressure
Closed Angle Glaucoma
- Closure of the iridocorneal angle
- Rapid onset of symptoms/ increase in introocular pressure
What are the two different fibers of the ciliary muscle?
1) Longitudinal
2) Circular
Longitudinal Fibers of Ciliary Muscle
Pull on lens to flatten for far vision
Circular Fiber of Ciliary Muscle
Reduce tension on lens for near vision
Choroid
- Dark layer of the posterior eye that is between the sclera & retina
- Provides nutrition to both layers
- Heavily pigmented by melanocytes
- Functions to reduce glare
What are the two layers of the choroid?
1) Choriocapillary layer= (outer) vascular layer of the choroid
2) Bruch’s Membrane (inner)
What are the five layers of bruch’s membrane?
Bruch’s membrane is the basement membrane for the capillaries of the choroid
1) Basement membrane for capillaries
2) Collagen Layer
3) Elastic Layer
4) Collagen Layer
5) Basement membrane for RPE
Neural Retina
Innermost layer of the retina
- Non-photosenstive= anterior to ora serrata
- Photosensitive= posterior to ora seratta
Fovea
- Point of greatest visual acuity
- Thinnest part of retina
- Cones only
Optic Disc
- Blind spot where the optic nerve exits the eye
- No photoreceptors
Macula Lutea
Yellow area that surrounds the fovea
RPE
- Retinal Pigmented Epithelium
- Heavily pigmented
- Controls nutrient delivery & waste removal to/from the retina
Detached Retina
Mechanical separation of the neural retina & RPE
What are the four groups of cells found in the retina?
1) Photoreceptors
2) Conducting Neurons
3) Association & Other Neurons
4) Support Cells
Photoreceptors
- Rods
- Cones
Conducting Neurons
- Bipolar Neurons= synapse between photoreceptor & ganglion
- Ganglion= synapse between bipolar neuron & optic nerve
Association & other neurons
- Horizontal
- Centrifugal
- Interplexiform
- Amacrine
Supporting Cells
- Muller= transport nutrients to rods & cones
- Microglia
- Astrocytes
What are the 10 layers of the retina?
1) RPE
2) Rods & Cones
3) Outer Limited Membrane (apical muller cells)
4) Cell Bodies of the Rods & Cones
5) Outer Plexiform Layer (synapse to bipolar cells)
6) Inner Nuclear Layer (Bipolar cell bodies)
7) Inner Plexiform Layer (Synapse to ganglion cells)
8) Ganglion Cell Layer (Cell bodies of ganglion)
9) Optic Nerve Fibers (Axons of ganglion)
10) Inner Limiting Membrane (Basement membrane of muller cells)
RPE
- simple cuboidal cells
- villi intermesh with rods & cones to remove waste/ discs (restores photosensitivity)
Rods
- low intensity light (black, gray, white)
- most abundant
- shed discs
- plasma membrane is continuous
- rhodopsin
Cones
- high intensity light (red, green, blue)
- shed discs, but not as much as rods
- less numerous
- plasma membrane is discontinuous
- iodopsin
Outer-segment of photoreceptors
photosensitive discs
Inter-segment of photoreceptors
machinery of the cell
Diabetic Retinopathy
- Most common cause of blindness in developed countries
- Elevated glucose causes blood vessels to become fragile & bleed, inducing edema & neovascularization
Neovascularization
Formation of new blood vessels
Non-Proliferative vs. Proliferative Diabetic Retinopathy
- Non-proliferative= NO neovascularization
- Proliferative= Neovascularization
Age Related Macular Degeneration
- Macula & Fovea Centralis start to degenerate
- Characterized by Drusen
- Macular edema
- Intra-retinal bleeding
Drusen
- Hallmark of macular degeneration
- Lipid accumulation in macula
Dry vs. Wet Macular Degeneration
Dry= No neovascularzation Wet= Neovascularization
What are the three parts of the lens?
1) Lens Capsule
2) Equatorial Zone
3) Subcapsular Epithelium
Lens Capsule
- Acellular
- Basement membrane of lens
- Outside
- Composed of type IV collagen & proteoglycans
Equatorial Zone of Lens
- Contains the germinal zone that creates new lens fibers
- Consists of a simple cuboidal epithelium
Crystallin
Protein in lens fibers
Cataracts
Elasticity changes of the lens with age & an increase in opacity
Vitreous Body
- 99% H20
- 1% gel
- Very slow to exchange oxygen & nutrients (can be used forensically)
- Should be clear, but dehydration can lead to collagen break-off causing floaters
Palpebral Conjunctiva
- Conjunctive lining the eyelid
- Stratified columnar epithelium with goblet cells
Bulbar Conjunctiva
Reflection of the conjunctiva onto the eyeball itself
