The eye Flashcards
what is the space between the eyeball and eyelid ?
the space between eyeball and eyelid is called the conjunctival sac
What are the three main layers of the eye ?
1) sclera , cornea
2) Uvea ( choroid ,Cilliary body, iris )
3) Retina ( inner layer )
outline the anatomy of the sclera and cornea
1) Sclera and cornea are covering of the eye
2) Cornea is colourless and transparent , sclera is white and tough dense CT
3) Limbus = boundary between cornea and sclera = zone of transition of epithelium of the conjunctiva with that of the cornea
UVEA anatomy (4)
1) vascular layer of the eye
2) contains the choroid, cilliary body and iris
3) anterior portion contains smooth muscle to constrict and dilate the iris
4) cilliary body = tension for the suspensory ligaments of the lense
Retina eyeball
1) 2 layers - outer pigmented layer and inner retinal layer
2) Anterior 1/3 of retina is not light sensitive , separated by ORA errata
3) Posterior = 2/3 is light sensitive and contains photoreceptors and neurones (rod and cones)
Cornea anatomy outline
5 layers
1) anterior surface = epithelium is stratified squamous non keratinising
2) Bownan’s layer = Bowman’s layer ) basement layer
3) Stroma
4) Descemet’s Membrane =basement membrane to endothelial cells
5) Corneal Endothelium = at the bottom , has aqueous humour beneath it
Iris anatomy
1) Anterior limiting layer
- fibroblast and melanocytes
2) Stroma which contains the blood vessels and melanocytes
3) Pupil dilator muscles and pigmented
Cilliary body in the UVEA
1) aqueous humour is produced by epithelium lining the cilliary processes
2) Aqu passes from posterior to anterior ->drains through the canal Schlemm –>contraction of the cilliary muscle
3) Smooth muscles
outline the lens anatomy
1) Capsule = basement membrane of lens epithelium
2)Older cells pushed to the middle = differentiate, nuclei lost cells = filled with crystalise proteins
lense fibres = Accumalation of debris => cataracts can be caused by this
what is the blood supply to the eye ?
internal carotid branches include the ophthalmic artery which branches into the the:
- central retinal artery ( end artery so if its damaged that’s it !)
- it supplied the inner 2/3 of the Retina
- Choroid and ciliary bodies + IRIS = UVEA is supplied by the branches of the ophthalmic artery :
- long , short posterior cilliary
- anterior cilliary artery
how can we see papilloedema ( due to raised ICP in the eye )?
1) the Optic nerve is surrounded by Dura matter and arachnoid sheaths
2) Raised ICP—> subarachnoid space so it squashes the thin central retinal vein –> papilloedema .
What is the retinal pigmented epithelium?
RPE is a single layer of post-mitotic cells, which functions both as a selective barrier to and a vegetative regulator of the overlying photoreceptor layer, thereby playing a key role in its maintenance.
- Hexagonally packed, Tight junction connected , single sheets of cells
1) melanin granules which absorb scattered light
2) organelles for digestion of photoreceptor outer segment ( phagosomes )
3) nourish the photoreceptors
4) contains retinal isomerase = recycles 11-cis retina
5) secretes growth factors ( maintains capillaries)
- forms the blood retinal barrier
what are the layers of the Retina
1) Choroid
2) Branch membrane which is a basement membrane
3) RPE
4) microvilli and sub retinal space
what is the function of the RPE ?
what about the oxygen extraction ?
1) They renew the photoreceptors outer segment –> free radicals
2) Relatively little oxygen is extracted here
3) absorbs light
4) phagocytose outer tips of photoreceptors
5) remakes the 11-cis retinal
What’s the visual cycle for rods ?
what does opsin do ?
What is the involvement of the RPE ?
1) photons are absorbed in the photoreceptors by 11-cis retinal
2) this causes a conformational change called bleaching
3) 11 cis retinal attaches to Opsin and changes into ALL-Trans retinal and Free opsin
opsin closes NA+ channels = less negative cells hyperpolarisation —> transmitted through the visual pathway .
so to absorb the light , rods need a supply of 11 -cis Retinal !
but they can’t remake 11 -cis retinal
so this is done in the Retinal Pigmental Epithelium !
