Eye I Flashcards
What are the three layers of the eye?
- Corneoscleral coat
- Uvea
- Retina
What are the two components of the corenoscleral coat?
Cornea and sclera
What are the three components of the uvea?
- Choroid
- Ciliary body
- Iris
What are the two components of the retina?
- Neural
2. retinal pigment epithelium
What is the blood supply to the eye?
Opthalmic artery
Where is the nonvisual part of the eye located (roughly)?
Anterior part of the eye (aura serrata)
What are the two divisions of the anterior segment of the eye?
Anterior and posterior chamber
What are the 6 components of the anterior segment of the eye?
- Aqueous Humor
- Iris
- Ciliary body and muscle
- Lens
- Cornea
- Anterior sclera
What is the posterior segment of the eye comprised of? What are its contents?
- Vitreous Chamber
Contents =
i. Vitreous Humor
ii. Visual retina
iii. Retinal Pigment Epithelium
iv. Posterior Sclera
v. Uvea
What is the main refractive unit of the eye? How much of the refractive power does it supply?
The cornea–2/3
What portion of the eyeball does the cornea comprise?
anterior 1/6
Is there vasculature in the cornea?
Negative
What are the 5 layers of the cornea?
- Corneal epithelium
- Bowman’s membrane
- Corneal stroma
- Descemets membrane
- Corneal endothelium
The corneal epithelium is a continuation of what?
The conjunctiva
What type of epithelial cell tissue is in the corneal epithelium? What type of attachments are here?
Non-keritinized Stratified squamous, attached via desmosomes
What is the mitotic activity of the corneal epithelium (high or low)?
High (eyes heal fast)
What are on the apex of the corneal cells? What is this structure’s function?
Microvilli, retain tears
Melanin is absent from the sclera. What is used instead for UV protection?
Ferritin
What is the innervation of the cornea?
CN V1
What is the basement membrane of the cornea called?
Bowman’s membrane
What type of cells are in Bowman’s membrane
None
Where does Bowman’s membrane end?
Corneoscleral limbus
What is the function of Bowman’s membrane?
Provide strength to the cornea, as well as a barrier
Damage to Bowman’s membrane can cause what?
Permanent scars = vision problems
What is in the corneal stroma?
Collagen fibrils arranged in lamellae
Proteoglycans
Collagen V
What percent of the cornea’s thickness is due to the corneal stroma?
90%
Disruption of the lammellar arragement of the corneal stroma produces what?
An opaque cornea
What is the posterior basement membrane of the cornea?
Descemet’s membrane
What is the function of Descemet’s membrane
Maintain curvature of cornea,
What type of epithelium comprises Descemet’s membrane?
Simple squamous epithelium with zonulae occludents
Does Bowman’s membrane regenerate? Does Descemet’s membrane.
Bowman’s no, Descemet’s yes
How does the corneal stroma remain visible?
Perpendicular stacking of collagen
Where does the corneal endothelium face?
The interior of the eye
What is the epithelium and junction type found in the corneal endothelium?
Simple squamous joined with zonula adherens, zonula occludens, and desmosomes
Injury to the corneal ENDOthelium results in what?
Opacity
What is the major function of the corneal endothelium?
e. Responsible for virtually all of the metabolic exchanges of the cornea
What is the “white” part of the eyeball?
Sclera
What portion of the eyeball does the sclera comprise?
5/6
What is the composition of the sclera?
Tough fibrous connective tissue (elastin and collagen)
What is the function of the sclera?
Protection and maintaining shape of the eye
What is Tenon’s capsule?
The fascial sheath over the eyeball to which the eye muscles attach
What is the episcleral space?
Space between Tenon’s capsule and the periorbital fat
What are the three layers of the sclera?
Episcleral
Tenon’s capsule
Suprachoroid lamina
What is the suprachoroid lamina?
The attachment of the sclera to the choroid for nutrition
What is the cornealscleral limbus?
The junction between the cornea and the sclera
Where are stem cells found in cornea? What is their purpose there?
At the cornealscleral limbus
Purpose is to replace sclera
What is the canal of Schlemm?
A sinus between Descemet’s membrane and the corneal stroma ONLY at the corneoscleral limbus
How does aqueous humor in the anterior chamber get into the venous system?
Through the Canal of Schlemm
What the angle that is formed between the iris and the cornea?
Iridocorneal angle
What are the three components of the uvea from anterior to posterior?
Iris
Ciliary body
Choroid
What is the uvea?
Inner vascular coat of the eye
What is the most anterior part of the uvea?
Iris
What is/are the part(s) of the iris that determines the pigment of the eye?
The anterior and posterior pigment epithelium (more = darker)
What are the two muscles of the iris?
Dilator pupillae
Sphincter pupillae
How are the dilator pupillae arranged?
Radially
When the dilator pupillae contracts, what happens to the pupil?
Dilates
What is innervation of the dilator pupillae and the sphincter pupillae?
Dilator = sympathetics
Sphincter = CN III
Where is aqueous humor produced?
The ciliary body
Where are the ciliary bodies located?
Around the iris
The ciliary body is anterior to what important structure in the eye?
Ora serrata
How many layers of epithelium are there in the ciliary body? Are they pigmented?
Two, one of which is pigmented
What type of epitheilium is present in the ciliary body?
Simple columnar x2, separated by a basement membrane
What is the function of the non-pigmented (inner layer) epithelium of the ciliary body?
Secrete aqueous humor
What is the pigment that is present in the outer layer of the ciliary body?
Melanin
What are the fibers that suspend the lens? Where do they attach to (besides the lens)?
Zonular fibers, which attach to the ciliary processes of the ciliary muscle
What is responsible for the blood-aqueous humor barrier?
Tight junctions between the ciliary process
Where is the aqueous humor produced? Absorbed?
Produced by outer layer of the ciliary body, absorbed by the canal of schlemm.
What is the name of the meshwork that is just in front of the canal of Schlemm?
Trabecular meshwork
What is open angle glaucoma?
A gradual loss of vision due to the gradual accumulation of aqueous humor, since it is not able to make it to the canal of Schlemm
What is angle closure glaucoma?
When the iris collapses against the cornea, causing a closure of the cornealsclereal angle. This impedes drainage of the aqueous humor
What are the three types of ciliary muscles?
- Longitudinal
- radial
- circular
What is the function of the radial ciliary muscles?
Flatten the lens, allow fo distal vision
What is the function of the circular ciliary muscles?
Reduce tension on the lens, allows for near vision
What is the function of the longitudinal ciliary muscles?
Stretch the choroid
What are the two major structures/cells in the choroid?
Vasculature and melanocytes
Where two structures does the choroid lie between?
The sclera and the retina
What is the choriocapillary layer of the choroid?
Vascular layer that sits deep.
What is Bruch;s membrane?
A thin membrane in the choroid that sits above the choriocapillary layer. and separates it from the retina
What are the 5 layers/ components of Bruch’s membrane?
- basal lamina
- collagen
- elastic
- collagen
- Basal lamina
Where is the NON-photosensitive region of the retina located?
anterior to the ora serrata and posterior surface of the iris
Where is the photosensitive region of the retina located?
Posterior to the ora serrata
Where is the point of greatest visual acuity in the retina? Why?
Fovea–thin in this area
What is the macula lutea?
The area that surrounds that fovea