Eye

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three layers of the eye wall

outer - corneoscleral coat
middle - vascular uvea
inner - photosensitive retina

space between the cornea and the iris

anterior chamber

space between the posterior surface of the iris and the anterior surface of the lens

posterior chamber

space between the posterior surface of the lens and of the neural retina

vitreous chamber

the anterior and posterior chambers contain a watery fluid called ___

aqueous humor

the ___ contains a transparent gel substance (hyaluronic acid and widely dispersed collagen fibers) called ___

vitreous chamber
vitreous humor

gives the eye its shape

vitreous humor

the outer or fibrous layer of the eye consists of the ___, the white portion, and the ___, the transparent portion
(these two layers are continuous)

sclera
cornea

___ is composed of dense, fibrous connective tissue that provides attachment for the extrinsic muscles of the eye

sclera

corneoscleral junction

limbus

an area of transition from the transparent collagen bundles of the cornea to the white opaque fibers of the sclera

limbus

- collagen bundles with interspersed fibroblasts
- nearly (but not completely) devoid of blood vessels
- bloodshot eyes are caused from dilated capillaries

sclera

protects cornea from UV, not melanin

ferritin

layers of the cornea

epithelium, NKSS
Bowman's membrane
corneal stroma
Descemet's membrane
endothelium, simple squamous

which layer of the cornea contains ferritin

epithelium

layer of the cornea that prevents spread of infections

Bowman's membrane

- thickest layer of the cornea
- collagen and elastic fibers with inerspersed fibroblasts

corneal stroma

basement membrane of the cornea

Descemet's membrane

secretes Descemet's membrane

endothelium, simple squamous

parts of the middle vascular uvea

choriod
ciliary body
iris

highly vascularized layer that provides nutrients for the underlying retina

choroid

highly vascular layer of connective tissue containing melanocytes that prevent the reflection of incident light

choroid

- contains pigment
- abundant melanocytes give its characteristic black colour
- makes pupil look black

choroid

anterior rim of the uveal layer continues forward, where it forms the stroma of the ___

ciliary body and iris

ring-like thickening of the choroid

ciliary body

within the ___ is the ciliary muscle

ciliary body

contraction of the ___ changes the shape of the lens, which enables it to bring light rays from different distances to focus on the retina

ciliary muscle

ciliary body has ~70 ciliary processes that form the ___ of the lens

suspensory ligaments

two layers of ciliary body epithelia

outer non-pegmented
inner pigmented

refraction by the lens

accommodation

accommodation is controlled by contraction and relaxation of the ___

ciliary muscle

___ of the ciliary muscle causes the lens to become thicker, now the eye is focused on near objects

contraction

___ of the ciliary muscle causes the lens to become flatter

relaxation

___ control accomodation of the lens to focus on near objects

ciliary muscles

regulates the amount of light that enters the eye

iris

- contractile diaphragm that extends over the anterior surface of the lens
- extension of the choroid

iris

___ forms the coloured, visible part of the eye in front of the lens

iris

contains smooth muscle and melanin-containing pigment cells scattered in the connective tissue

iris

- give eye its color
- block light entering eye except through pupil

melanocytes

in contribution of eye colour, fewest melanocytes give rise to ___ eyes and most melanocytes give rise to ___ eyes

blue
brown/black

activation of parasympathetic fibers to ___ (circular) muscles of the iris causes them to contract, decreasing pupil size

sphincter pupillae

activation of sympathetic fibers to ___ (radial) muscles of the iris causes them to contract, increasing pupil size

dilator pupillae

does the iris receive sympathetic or parasympathetic innervation?

both

the parasympathetic nerve fibers from CN III innervate the ___ as well as the ___ for lens accommodation

- pupillary constrictor (sphincter) muscles
- ciliary apparatus

- ___ inserts via the suspensory ligaments on to the periphery of the lens capsule
- regulates the shape of the lens

ciliary muscle

- ___ muscle of iris is a sphincter
- when contracted, constricts the pupil

circular

- ___ muscle of iris when contracted, dilates the pupil

radial

___ (facing posterior chamber) transports a protein poor plasma from fenestrated capillaries into posterior chamber of eye forms aqueous humor
- similar in ionic composition to plasma but contains less than 0.1%protein, compared with 7% protein in plasma

outer non-pigmented layer of ciliary processes

aqueous humor is produced by the ___

ciliary processes

___ is produced by ciliary epithelium in posterior chamber, flows into anterior chamber

aqueous humor

from anterior chamber, aqueous humor goes from ___ directly into the venous system

Canal of Schlemm

___ provides nutrients and oxygen for the lens and the cornea

aqueous humor

- damage to the optic nerve
- clinical condition resulting from increased intraocular pressure

glaucoma

___ can be caused by excessive secretion of aqueous humor or impedance of the drainage of aqueous humor from the anterior chamber

glaucoma

vision loss due to glaucoma is caused by damage to the ___

optic nerve

The entire surface of the lens is smooth and shiny, contains no blood vessels, and is encased in an elastic membrane, collagen type ___.

IV

the lens capsule is primarily ___ collagen

type IV

what are lens fibers?

cells that have lost their nuclei and organelles, becoming thin, elongated, transparent structures

where are crystallins found?

crystallins are found in lens fibers

___ are ...
- among the longest-lived proteins in the body
- formed in utero and persist for the life of the individual
- lens also keeps growing throughout life and also make new ___

crystallins
crystallins

lens capsule is a thick basement membrane containing ___ and ___

collagen type IV
laminin

loss of transparency of the lens or lens capsule

cataracts

___ that significantly impair vision can usually be corrected surgically by removing the lens and replacing it with a plastic lens

cataracts

innermost, photosensitive layer

retina

the chief refractive element in the eye

cornea

___ of the anterior and posterior chambers (minor role in difraction, however plays an important role in nourishing the avascular lens and cornea)

aqueous humor

2nd in importance to the cornea in diffraction

lens

minor role in diffraction

vitreous body

emmetriopia

normal, ideal

myopia

near-sighted

cornea is too thick or eyeball is too long

myopia

hyperopia

far-sighted

condition of unequal curvatures along the different meridians in one or more of the refractive surfaces (cornea, anterior or posterior surface of the lens) of the eye, in consequence of which the rays from a luminous point are not focused at a single point on the retina

astigmatism

in LASIK surgery, pulses from a computer-controlled laser vaporize a portion of the ___ and the flap is replaced

stroma of the cornea

in LASIK surgery, the cornea is made flatter to treat ___,
steeper to treat ___
and/or more spherical to correct ___ errors

nearsightedness
farsightedness
astigmatism

derived from inner layer of optic cup

neural retina

derived from outer layer of optic cup

pigment epithelial layer

- inner layer that contains the photoreceptors
- from inner cup

neural retina

- outer layer that rests on the choroid
- from outer cup

retinal pigmented epithelium

___ are specialized receptors for dim light

rods

- ___ specialized receptors for bright light reception
- also perceive color (3 types, each recognizes either red, green, or blue pigment)

cones

shallow depression located about 2.5 mm lateral to the optic disc

fovea

area of greatest visual acuity

fovea

Cones are highly concentrated in the ___

fovea

yellow-pigmented zone that encircles the fovea

macula

exit site for the optic nerve

optic disk

contains no photoreceptor cells and is called the "blind spot" of the retina

optic disk

- in rods
- molecules in the outer-segments discs absorb photons

rhodopsin

- in cones
- molecules in the outer-segments discs absorb photons

iodopsin

- rods
- photon absorption leads to the ___ of Na+ channels in the plasma membrane, which (hypopolarize/hyperpolarize)
the membrane and reduces the rate of inhibitory neurotransmitter release from the synaptic region

closure
hyperpolarize

chromatophore of rods is a vitamin A-derived carotenoid called ___, thus adequate intake of vitamin A is essential for normal vision

retinal

opsin + retinal =

rhodopsin

The process of breakdown activates the receptor protein which in turn, becomes able to activate a Gt protein, ___, bound to the inner face of the membranes of the photoreceptor discs. The activated G-protein releases the G-alpha subunit, to activate a cGMP phosphodiesterase, that breaks down cGMP

transducin

in rods, cGMP causes channels to ___, light results in their ___

open
closing

cell layers of the retina

horizontal
bipolar
amacrine
Müller's
ganglion

interspersed between photoreceptor cells and ganglion cells

bipolar cells

- synapse with the synaptic junctions between the photoreceptor cells and the bipolar cells

horizontal cells

processes of ___ branch extensively to provide sites of synaptic connections with axonal endings of bipolar cells and dendrites of ganglion cells

amacrine cells

- large, multipolar neurons
- axons of these neurons pass to the brain

ganglion cells

- neuroglial cells
- supporting cells for the neural retina

Müller cells

loss of vision in the center of the visual field because of damage to the retina

age-related macular degeneration

The ___ form of advanced AMD results from atrophy to the retinal pigment epithelial layer below the retina, which causes vision loss through loss of photoreceptors (rods and cones) in the central part of the eye

dry

drusen have a similar composition to ___ plaques, and their formation also seems to involve inflammation mediators

atherosclerotic

___ form of AMD causes vision loss due to abnormal blood vessel growth in the choriocapillaris, through Bruch's membrane, ultimately leading to blood and protein leakage below the macula

wet

Anti-angiogenics or ___ agents can cause regression of the abnormal blood vessels and improvement of vision when injected directly into the vitreous humor of the eye

anti-VEGF, anti-Vascular Endothelial Growth Factor

transparent mucous membrane that lines the inner surface of the eyelids and covers the sclera of the anterior portion of the eye

conjunctiva

inner surface of the eyelids

palpebral conjunctiva

sclera of the anterior portion of the eye

bulbar conjunctiva

The conjunctiva is a clear mucous membrane consisting of cells and underlying basement membrane that covers the sclera (white part of the eye) and lines the inside of the eyelids. It is composed of rare ___ epithelium

stratified columnar

___ is an inflammation of the conjunctiva usually associated with hyperemia and a discharge

conjunctivitis

- ciliary muscle fibers relaxed
- suspensory ligament taut
- lens ___ and focused for ___ vision

thin
distant

- ciliary muscle fibers contracted
- suspensory ligament relaxed
- lens ___ and focused for ___ vision

thick
close

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