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retina

Terms in this set (185)

inner neural layer of globe
retina
retina extends from
optic disc to ora serrata
function of retina
convert light energy into neural signal and carry the neural signal to brain via optic nerve
central retina/posterior pole
located between superior temporal and inferior temporal arteries
macula
responsible for central vision

fovea: in center, highest visual acuity
most anterior portion of optic nerve
optic disc (optic nerve head)
how is optic disc situated in relation to macula
nasal + slightly superior
the optic disc is slightly elongated __________
vertically
what is the orange color in the optic disc from
combination lamina cribosa and choroidal vasculature
depression in center of the optic nerve
optic cup
optic cup properties
varies in size and depth
blood vessels enter/exit the eye through the optic cup
far periphery
extends from ora serrata and the equator
ora serrata
termination of peripheral retina (most anterior portion of the retina)

transition between peripheral retina and CB
3 types of cells in the retina
epithelial - RPE
neurons (nerve cells)
neuroglial cells
neuroglial cells
muller, microglial, astrocytes
neurons (nerve cells)
photoreceptors, horizontal cells, bipolar, amacrine, ganglion
RPE located between
photoreceptors + choroid (specifically choricicapillaris)
RPE is arranged in single layer
homogenous
RPE

columnar cell
cubodial cell

locations
columnar cell: posterior pole
cubodial cell: near ora serrata (transition to pigmented epithelium of ciliary body)
apical aspect of RPE contents (this is what is in contact with photoreceptor outer segments)
microvili + tight junctions
basal aspect of RPE
attaches to BM that forms most inner layer of bruch's membrane
pigmentation of RPE is due to what three things
melanin
lipofuscin
xanthophylls - leutin and zeaxanthin
melanin

where densest in retina
macula (+ present more in darker skinned individuals)
melanin function
UV radiation
lipofuscin

composition
fluorescent compounds, lipids, proteins
lipofuscin where present
in lysosomes of RPE cells
lipofuscin

where from
incompletely digested photoreceptor outer segments --> accumulates WITH AGE (wear and tear pigment)
yellow plant pigment
xanthophyll
two types of xanthophylls in the retina
leutin and zeaxanthin
where are leutin and zeaxanthin present
RPE cells + outer segments of photoreceptors
located throughout retina, but highest concentration in macula
where are leutin and zeaxanthin highest concentration
macula
leutin and zeaxanthin accumulate from
dietary sources
leutin and zeaxanthin
two functions
filter (absorb short wavelengths visible light (blue) to REDUCE chromatic aberation)
antioxidant effect (help prevent DNA damage at macula)
functions of RPE (6)
1) transport nutrients and remove waste from outer retinal layers (photoreceptors)
2) metabolize and store vitamin A (for photoreceptors to use)
3) phagocytose photoreceptor outer segment discs
4) produce interphotoreceptor matrix (IPM)
5) produce growth factors
6) melanin - absorb excess visible light + UV radiation
nutrients enter RPE through ________, exit through _____________
choricocapillaries, choricocapillaries
tight junctions help RPE cells selectively control movement of nutrients/waste, what does this contribute to
blood-retinal barrier (BRB)
how do glucose and lactate move through RPE
carrier proteins
Each RPE cell interacts with ________ photoreceptors.
30-40
role of vitamin A
necessary for phototransduction
Phototransduction
converting light into neural signals
RPE cells have lysosomes that enable cell to ingest as many as _______ discs daily and if there is undigested material that accumulates as deposits of __________
RPE cells have lysosomes that enable cell to ingest as many as 2000 discs daily and if there is undigested material that accumulates as deposits of LIPOFUSCIN
interphotoreceptor matrix is composed of
GAGS/proteoglycans (which are produced by RPE cells)
what does IPM surround
apex of RPE cells and outer and inner segments of photoreceptors
roles of the interphotoreceptor matrix (IPM) (3)
1) adhesive properties (hold RPE and photoreceptors in close proximity)
2) exchange of metabolites between RPE and photoreceptors
3) orient photoreceptor outer segments toward pupil for optimal light capture
role of growth factors in RPE
maintain choricocapillaries
mealin in RPE role
reduce light scatter
protects against UV damage
specialized neurons that convert light energy into neural signal
photoreceptors (rods + cones)
rods highest density
periphery
cones highest density
macula (fovea ALL CONES)
do we have more rods or cones
rods
6 region of photoreceptor (outer to inner)
outer segment
cilium
inner segment
outer fiber
cell body
inner fiber
outer segment (photoreceptors)
associated closely with RPE
stacjs of flattened discs surrounded by lipid bilayer - each disc containing visual pigments

phototransdicution occurs at disc
cilium is composed of
microtubules (proteins)
what does cilium do
acts as conduit for metabolites between inner and outer segment
inner segment produces components of ______- segment
outer
portion of inner segment closest to outer segment is called
ellipsoid (numerous mitochondria)
portion of inner segment closes to cell body is called
myloid
myloid contains
endoplasmic reticulum + golgi apparatus)
cell body contains
nycleus
Inner fiber of photoreceptor
axon of photoreceptor
axon terminals are invaginated and contain presynaptic vesicles - synaptic ribbons hold vesicles close to the terminal
send neural signal to bipolar and horizontal cells - glutamate (neurotransmitter)
rods

visual pigment
discs width
diplacement
visual pigment: rhodopsin (496 nm (blue green))
discs width: uniform width
displacement: gradually displaced outward by formation of new discs
shedding of rods
shed regularly, a lot in the morning
cones

discs shape
lifespan of discs
discs: wider at base than apex
lifespan of discs: longer lifespan (Unknown how discs are sheds and produced)
cones visual pigment
420 nm *blue)
521 nm (green)
588 nm (red)
588 nm
red
521 nm
green
420 nm
blue
within the inner segment, ________ have more mitochondria than ___________
within the inner segment, CONES have more mitochondria than RODS
outer fiber ________ have even shorter or even absent outer fibers (______ nuclei lie outside _____ nuclei)
cones, cones, rod
inner fiber

how rods terminate
spherule (rounded, pair shape)
inner fibers

cone termination broad, flattened structure
pedicle
rods (inner fiber)
___ invagination, ___ synaptic ribons
up to _____ neuronal terminals may be embedded into ____ spherule
1 invagination, 2 synaptic ribons
up to 5 neuronal terminals may be embedded into 1 spherule
cones (inner fiber)
___ invagination, ___ synaptic ribons
up to _____ neuronal terminals may be embedded into ____ spherule
4-8 invagination, (?) synaptic ribons
up to 3 neuronal terminals may be embedded into invagination (triad)
connects cones to cones and cones to rods through gap junctions
telodendria

processes that extend from pedicle
Rods are responsible for ___ vision.
scotopic
Cones are responsible for ___ vision.
photopic
scotopic vision
vision in dim/darkness
photopic vision
vision in bright light
scotopic vision properties
fine detail poor
color vision absent
photopic vision properties
ability to see fine detail
discriminate colors
horizontal cells

dendrites
axons
dendrites: extend horizontally
axons: may or may not be present
horizontal cell function
integrate + regulate the input from several photoreceptors
bipolar cells

axon
dendrite
axon: send neural signal to AMACRINE and ganglion cells (release by glutamate)

dendrites: recieve infro from photoreceptors
most bipolar cells synapse with
ganglion cells
amacrine are inner to _______ cells
bipolar
recieves infro from bipolar cells + sends signals to ganglion cells

also receives signals from amacrine cells
amacrine cells
what neurotransmitter do amacrine cells release
GABA or glycine
final retinal destination for neural signal
ganglion cells
ganglion cells receive info at its dendrites from
bipolar and amacrine cells
what two cells integrate and modify signal
horizontal + amacrine
central retina has _________ ratio of cones: bipolar: ganglion
1:1:1

NO CONVERGENCE
information from ________ rods and _______ cones is transferred to each ganglion cell
~100 RODS
4-6 CONES

CONVERGENCE
central retina have convergence?
NO
axons from ganglion cells carry the retinal neural signal to the brain via the optic nerve

form bundles, converge at optic disc and from the optic nerve

optic nerve courses from eye to ________ to synapse in the -_________________

and release neurotransmitter __________
axons from ganglion cells carry the retinal neural signal to the brain via the optic nerve

form bundles, converge at optic disc and from the optic nerve

optic nerve courses from eye to THALAMUS to synapse in the -LATERAL GENICULATE NUCLEUS

and release neurotransmitter GLUTAMATE
muller cells ; how extend
10 million cells that extend from the photoreceptor inner segments to the inner retinal surface (extends inner segment to vitreous)
apical aspect of muller cells
located between inner segments of rods and cones
basal aspect of muller cells
inner retinal surface (vitreous)
predominating supporting glial cell of retina
muller cells
roles of muller cells (4)
1) structural support for retinal neurons
2) maintain extracellular pH by absorbing metabolic waste products
3) recycle neurotransmitters released by retinal neurons
4) form inner limiting membrane
innermost boundary of retina
Internal limiting membrane
inner limiting membrane
consists of termination of muller cell processes (footplates) covered by a basement membrane
microglial cells (retina)
wandering phagocytic cells -> eat up waste in retina

increase in number during inflammation and injury
astrocytes

shape + where found
star shaped fibrous cells found near ganglion cell bodies + axons
astrocytes role in retina
form a supportive network that encircles ganglion cell axons --> also encircle retinal capillaries present near ganglion cell bodies + axons
may perform the same function as muller cells
astrocytes
RPE forms a gap (subretinal space) between RPE and photoreceptors but is held in close proximity through (4)
1) microvilli on apical surface (envelop outer segment tips of photoreceptors)
2) interphotoreceptor matrix (IPM) (adhesive properties)
3) intraocular pressure (produce/created from aqueous humor)
4) presence of vitreous (+/-)
what happens if intraocular pressure drops low in RPE
can have retinal detachment -> not enough pressure to keep retina in contact with RPE
most common space of neurosensory retinal detachment
subretinal space

due to minimal connection
photoreceptor LAYER

made up of what two things
what extend here
only inner and outer segment of photoreceptors

projections of muller cells extend between inner segments
outer limiting membrane (OLM) or External Limiting membrane

composed of ________- which is between adjacent ______ and ____________
composed of ZONULA ADHERENS which is between adjacent PHOTORECEPTORS and MULLER CELLS
outer nuclear layer

composed of
photoreceptor cell bodies
cones in outer nuclear layer (ONL)
cone nuclei lie in SINGLE LAYER CLOSE TO ELM (external limiting membrane)
rods in outer nuclear layer
arranged in several rows INNER to cone bodies
how do rods in the outer nuclear layer lie
inner to cone bodies
outer plexiform layer (opl) composed of synapses between
photoreceptor axons and bipolar dendrites + horizontal cell processes

horizontal cell processes and bipolar dendrites
outer plexiform layer (OPL)

what sort of attachment is between bipolar dendrites and horizontal cell processes? what does it resemble?
they have desmosome-like attachments

resembles a discontinuous membrane
the attachments between the bipolar dendrites and horizontal cell processes are sometimes called the
middle limiting membrane
middle limiting membrane is NOT it's own layer, it's a part of the ________ layer
outer plexiform layer
middle limiting membrane
border between inner and outer retina blood supply
inner nuclear layer (INL)

what cells present here
cell bodies of bipolar, horizontal, amacrine, muller cells
inner plexiform layer (IPL)

have synapses between
bipolar axons + amacrine processes
bipolar axons + ganglion dendrites + cell bodies

amacrine processes + gangloin dendrites + cell bodies
amacrine processes + amacrine processes
ganglion cell layer (GCL)

composed of
ganglion cell bodies (single layer with cells side by side and muller cell processes between them)

some displaced amacrine + muller bodies may be present here
nerve fiber layer (NFL)

is composed of
ganglion cell axons (nerve fibers)

axons form bundles as course PARALLEL to retinal surface and gather at optic disc
4 bundles of axons present in the nerve fiber layer (NFL)
papillomacular bundle
superior temporal and inferior temporal bundles
nasal bundle
papillomacular bundle
macular fibers course from CENTER of fovea directly to temporal margin of optic disc
comprise 90% of all axons in the optic nerve
superior and inferior temporal bundles
arch around papillomacular bundles to superior and inferior margins of the optic disc

respect the temporal raphe

form an arcuate pattern
superior and inferior temporal bundles help form a __________ pattern
arcuate pattern
temporal raphe
horizontal seam between the superior and inferior RNFL
nasal bundle
course in radial pattern toward NASAL margin of optic disc
once optic nerve fibers reach the optic disc, they turn at a _______ angle, and exit the eye through the lamina cribosa as the optic nerve
right
internal limiting membrnae (ILM)

what terminates here
mullers cell processes (footplates) covered by a basement membrane

vitresous in contact with the iLM
what part of the retina makes up most of it

peripheral or central?
peripheral
peripheral retina is anterior or posterior
anterior
peripheral retina

rods or cones dominate here
rods
rods are designs for detecting _______________ and ___________ motion
gross and motor
does peripheral retina have convergence?
yes
convergence of peripheral retina
bipolar cells have larger dendritic trees (receive stimuli from up to 80 rods), single layer of ganglion cells
how many layers of ganglion cells does peripheral retina have? does the central retina have?
peripheral retina: single layer
central retina: 2-3 layers
where does peripheral retina terminate
at ora serata (transition between peripheral retina + CB)
when the peripheral retina terminates at the ora serata neural retina becomes
a single layer of columnar cells that continues as nonpigmented epithelium of CB

rods disappear and are replaced by malformed cones
nuclear layers merge with plexiform layers
ILM continues as the inner basemement membrane of ciliary body
RPE is continuous with _________________ at the ora serata
pigmented epithelium of the ciliary body
centeral retina/posterior pole histologically referred to as
macula lutea
central retina/posterior pole is between the _________ and __________________
superior and inferior temporal vascular arcades
histoligically centeral retina is defined by presence of what two things
two or more layers of ganglion cells

+

xanthophyll (leutin + zeaxanthin)
macula lutea/centeral retina/posterior pole subdivided into what layers
perifovea
parafovea
fovea
foveola

*layers determined by number and rows of cells in nuclear layers, not easily differentiated
perifovea
GCL (2-4 cells thick, towards periphery 1 thick)
parafovea what layers
INL, OPL, GCL
how thick INL in parafovea
12
GCL how thick in parafovea
7
fovea (clinically macula)

how appear physically in centeral retina
darkened regions, RPE cells taller and have more pigment than anywhere else in retina
foveola (clinically fovea)

why appear as depression
bipolar, horizontal, amacrine, ganglion cells displaced laterally

allows light to reach photoreceptors without interference of other retinal cells
what layers present in foveola (6)
RPE
photoreceptor layer
external limiting membrane
outer nuclear layer
inner limiting membrane
outer plexiform layer
foveola photoreceptor layer properties
only cones
outer segments elongated
foveola ONL
10 rows of cone nuclei w 1:1:1 cones : bipolar: ganglion
allows detailed info
outer plexiform layer of foveola aka
henle's fiver layer (OBLIQUELY ORIENTED CONE AXONS)
outer plexiform layer cone axon course oblique to reach displaced bipolar and horizontal cells
obliquely oriented cones = henle's fibers
does foveola have retina capillaries?
no, nourished by choricocapillaris

known as FAZ (foveal avascular zone)
FAZ (foveal avascular zone)
allows light to pass unobstructed into photoreceptor outer segment
site where ganglion cell axons (RNFL) accumulate and exit eye
optic disc / optic nerve head
optic disc lacks all retina elements except what layers
nerve fiber layer + inner limiting membrane
the optic disc has no photoreceptors
makes blind spot in visual field
dual blood supply to retina

1/3
2/3
1/3: part of retina avascular, receives blood from choroid
- posterior choroid: short posterior ciliary arteries
- anterior choroid: long posterior ciliary arteries + anterior ciliary arteries

inner 2/3: central retinal artery
choroid supplies outer 1/3 of retina which includes
RPE + photoreceptors
cilioretinal artery

prevalence
what it supplies
15-20% of population has it and it supplies inner 2/3 of retina
cilioretinal artery branch of
short posterior ciliary artery
exception: _________________ and _________________ supplied only by the choroid. thin enough to be supplied by diffusion from choroidal circulation
exception: EXTREME RETINAL PERIPHERY and FOVEAL AVASCULAR ZONE (FAZ) supplied only by the choroid. thin enough to be supplied by diffusion from choroidal circulation
what is the border between the inner and outer retina blood supply?
middle limiting membrane
middle limiting membrane part of
outer plexiform layer (OPL)
where does OPL receive blood supply?
choroid + central retinal artery
outer 1/3 of retina drained by
vortex veins
inner 2/3 of retina drained by
central retinal vein
outer 1/3 of retina drainage pathway
choriococapillaries -> sattlers -> hallers
4-7 vortex veins
travel through suprachorodial space -> pierce posterior sclera -> superior and inferior opthalmic veins
inner 2/3 of retina drainage pathway
deep capillary network -> venules -> 4 major branches of veins
***superior temporal, inferior temporal, superior nasal, inferior nasal

branches join at optic disc, travel with optic nerve fibers, and leave the eye as single vein (central retinal vein) -> superior opthalmic vein or directly into cavernous sinus
veins that drain the inner 2/3 of retina are located in
GCL or NFL
retinal vein's characteristics
- very thin wall (atypical for veins) - compression by arteries
-appear darker and larger than arteries
-low hydrostatic pressure (susceptible to occlusion if intraocular, intraorbital, or intracranial pressure is elevated)
-no overlap in regions drained by venules
veins darker than arteries because
veins carry deoxygenated blood
blood-retinal barrier function
prevent blood from freely entering retinal tissue (if blood enters retina, can impede light and affect vision)
blood-retinal barrier contributions
tight junctions join RPE cells ---> retinal capillary endothelial cells (CRA) are joined by tight junctions + nOT fenestrated (prevents large molecules from exiting retinal vessels)
inner BRB
vs

choricocapillaries
inner BRB: tight junctions, no fenestrations - prevent movement

choricocapillaries: no tight junctions, fenestrated - allow movement
phototransduction = constant process that occurs in photoreceptors + retina is extensive network of continual intracellular communication

so
require a lot of energy
what type of glucose metabolism occurs in photoreceptors
aerobic
oxygen utilization by photoreceptors is ___x higher than other CNS neurons

and why
3-4x higher

need to meet needs of photoreceptors, blood flow in choricocapillaries significantly higher than other tissues
primary source of energy is glucose metabolism

how does glucose move
move out of capillaries and into retinal tissue via facilitated diffusion
glucose transporters are located on the endothelium of retinal capillaries and on the apical and basal membranes of rpe
what cells store glycogen
muller cells

provide steady source of glycogen
role of highly active pentose phosphate pathway in photoreceptors
produce nADPH needed for visual pigment regeneration
produce electrons

involved in converting light energy to neural signal
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