Structure and function of the eye Flashcards
What are the 3 main bones of the orbit?
Lacrimal bone, ethmoid bone and frontal bone
(many holes at back-mainly superior orbital fissure
What is the space between the two eyelids? and the most lateral corner of the eye? What structure do you find in the medial canthus?
Palpebral fissure
Lateral canthus (the medial one is medial canthus
Caruncle
In the eye, how do you call the black center, coloured part and the white part? And the limit between the iris and sclera?
Pupil, iris, sclera
Limbus-limit between cornea and sclera, where stem cells lie
What keeps the eye wet?
Lacrimal system
What produces the tears in the lacrimal system?
Lacrimal gland above eye produce the tears, and they go to the eye. Then through caruncle, to canaliculi to tear sac and to nose
What is tear film and its use?
Maintain smooth cornea air siface-thin film of tars (lipid layer, water layer and mucin layer -siting on microvillia cells)-applied when we blink
Provides oxygen to cornea, clears debris
What is the conjungtiva? Where does it lie? What is it blood supply?
Thin transparent tissue that covers outer eye -begins at the outer edge of cornea and covers visible eye, and lines the inside of eye lids (Cant slip anything undereyelid)
Blood supply from tiny blood vessels that are invisible to naked eye (except if pathology, like conjungtivitis)
What muscle do you find around the eye?
Cilliary bodies around the lens modify its shape
Rectus muscle connect to cornea (on the outside)-move eye up and down
What are the exterior (to interior) layers of the eye? What are their main charateristics?
Sclera-hard and opaque-high water content (non sharp object hitting eye will break bone before eye)
choroid-pigmented and vascular
retina-neurosensory tissue
How does the cornea relate to the sclera? What is the cornea?
Transparent, dome shaped window. Continuation of the cornea-2/3 focusing power of the eye –low water content
Front-most part -also physical and infection barrier
What are the 5 layers of the cornea?
Epithelium-bowmans membrane, stroma (thick transparent), descemet’s membrane, endothelium (decrease with age)
Its pretty musch stroma sandwiched by cells, and their basal membrane (weird names)
What is the Uvea? What is it composed of?
vascular coat of eye ball-3 parts–Iris, cilliary body and choroid
They are connected and diseases of one can affect the others - can differentiate between disease of anterior/middle posterior diseases by seeing where opaque liquid is
What is the choroid?
Lies between of the retina and sclera, and composes of layers of blood vessels that nourish the BACK of the eye
What is the iris?
Anterior part of the Uvea-controles light levels inside the eye. The opening in the center is called the pupil
Muscle around dilate and contrict iris
Controls luminosity and depth of field
What is the lens? How does it change it shape?
Acellular capsule made mostly of collagens-regular elongated cell fibres (cataract if lose transparency)
Important refractive power (1/3 of eye)-
Elastic, so can accomodate-shift the focus by distorting its shape
Cilliary muscle connect to lens, which is suspended by fibrous rings nown as zonules by them. They can modify (pull/push). When contract, push the zonules closer and thicken lens
What is the retina?
Very thin layer of tissue that lines inner eye
Responsible for capturing light rays -and send them to the brain via the optic nerbe
What is the optic nerve?
Transmits electrical signal to brain from eye
Connects to eye near macula-at the back of the eye-visible part is called optic disc
What is the macula?
Located roughly center of retina-temporal to optic nerve
Small and highly sensitive part of retina-detailed central vision-like reading
Center called the fovea-highest amount of cones and good ration of ganglionic cells to photoreceptors (lowest amount of rods-)
What are the two anatomical segments of the eye
Anterior segment-between cornea and less-filled with clear aqueous fluid
Posterior segment-between lens and rest of eye
What can you find within the cilliary bodies>
Cilliary muscles at the back, but also secrete aquerous fluid of the eye
Flows towards anterior chamber-along the iris, via pupil
Supplies the nutrients-the oxygen is gotten rom air
Trabecular meshwork drains the fluid out-via canal of schlemm (80%-rest is aborbed)
What is glaucoma?
Sustained rise of intraoccular pressure-risk factor (if anything pressures the eye, higher chance to damage the rest)
Retinal ganglion cell death and optic disc cupping-visual field loss, blindness
Eye is closed structure, so either reduce prod or increase drainage
–will lose part of vision, but brain fills the gap-so sometimes would just miss out of cars coming)
What are the different types of glaucoma?
Primary open angle glaucoma (commenest)-trabecular network dysfunction
Closed angle glaucoma-acute or chronic
What are the differences between blood vessels you can see in the ey?
veins are thicker and darker, arterioles are smaller and thinner
What is the optic nerve blind spot?
So specialised-doesnt have photoreceptors
So imaged on the nerve doesnt reach the brain
