8. Retinal anatomy. Back of the eye in normal conditions. Flashcards
how transparent is the retina ?
semitransparent
what is the macroscopic colour of the retina ?
appears purplish red
how much does the retina extend ?
from the optic disc to the ora serrata
what are the distinct regions of the retina ?
optic disc - here the optic nerves leave the eye
axons of the ganglia cells gather together and form the optic nerve and leva the ey via the optic disk
BLIND SPOT - no rods or cones
entry point of blood vessels supplying the retina
macula lutea- central vision
- oval shaped pigmented area
parafoveal region , fovea centralis - most sensitive part of the retina ,
foveola
umbo - tiny depression at the centre of the foveola
peripheral retina - side vision
- near periphery
- mid peripheral
- far periphery - contains periwig of vortex veins
- ora serrata
all the retinal layers terminate where ?
at the optic disc , except the nerve fibre which passes through lamina cribrosa
where is the macula lute located ?
the posterioir pole of the eyeball temporal to the optic disc
what is the function of the macula lutea?
central , high resolution , colour vision , possible in goodlight
why does the macula have a different colour to the rest of the retina ?
zeaxanthin predominates at the macula , while lutein preodimantes everywhere else in the retina
that is why macula has different colour and easily seen in ophthalmoscopy
mainly the macula contain what ?
cones and no rods responsible for colour vision
the macula contains fovea centralis which is what ?
thinning of the retina - no ganglion cell layer and no nerve fibre layer - strongly exposed to light because of these layers being absent
many cones , no rods
which is the location for the highest reolutio of our vision ?
fovea centralis
how many layers does the retina have ?
10
what re the layers of the retina ?
from the closest to the farthest of the vitreous body - or from where the light first hits
inner limiting membrane - basment membrane elaborated by muller cells (retinal glial cels - maintain the structural and functional stability of retinal cells)
nerve fibre layer - axons of the ganglion cell nuclei - they become the optic nerve
ganglion cell layer - nuclei f ganglion cells
inner molecular plexiform layer
synapse between bipolar cells axons and dendrites of ganglion and amercing cells
inner nuclear layer - contains nuclei and surrounding cell bodies of bipolar cells , amercing cells and horizontal cells
outer molecular plexiform layer - projections of rods and cones
ending as rod spherule
and cone pedicle
making synapse with the dendrites of bipolar cells
macular region known as fiber layer of henle
outer nuclear layer - cell bodies of rods and cones
external limiting membrane - layer separating the inner segment portions of the photoreceptors from their cell nucleus
layer of rods and cones
outer segment - metabolic portion of photoreceptor cells such as the mitochondria
inner segment - photosensitive parts of rods and cones
retinal pigment epithelium - single layer of cuboidal cells
retinal pigment epithelium
what is the diameter of the macula ?
0.35um
vertebrate retina is inverted what does that mean ?
light sensing cells are in back of the retina, so that light has to pass through layers of neurons and capillaries before it reaches the rods and cones.
but overlying neural fibre layer does not degrade vision in the inverted retina. The neurons are transparent and the accompanying glial cells have been shown to act as fibre-optic channels to transport photons directly to the photoreceptors
impulse produced is in the opposite direction of the light
