The Retina Flashcards
How many layers does the retina consist of?
9
Light passes through the entire layer of the retina prior to what?
stimulating rods and cones.
What are rods and cones for?
To perceive light.
What is the macula?
An oval shaped and highly pigmented yellow spot in the central portion of the retina.
What does the macula surround?
The fovea, parafovea, and perifovea.
What does the macula serve as?
A protective filter over the fovea.
What does the macula contain?
xanthophylls, carotenoids, lutein
What does the macula observe?
Excess light entering the eye including UV rays.
Where is the fovea?
A small indented area of the center of the retina.
What does the fovea contain, in terms of rods and cones?
it has only cones and a few or NO rods.
What is in the central portion of the fovea or foveola?
Has exclusively cones that are more tightly packed than other areas.
What are characteristics of the cones in the foveola?
They are uniquely long and slender.
What characteristics do cones in the peripheral area contain?
They are usually wide
What surrounds the fovea?
The parafovea and the perifovea
The structure of the fovea prevents what?
significant reduction of visual acuity.
Where is the pigment epithelium?
The outermost layer of the retina.
The pigment epithelium is not apart of what?
The neurosensory of the retina.
What does the pigment epithelium contain?
single layer of hexagonal cells densely paced with dark or brown granules.
What do the granules of the epithelium contain?
Melanin and lipofucsin.
What is lacking in albines in the retinal pigment epithelial?
pigment granules.
How are the pigment epithelial cells arranged?
extend straight threadlike processes between the rods and cones.
What does the cytoplasm of the pigment epithelial cells contain?
Vitamin A .
What vitamin is present in the cytoplasm of rods and cones as well?
Vitamin A
What does the pigment epithelium prevent?
Light reflection throughout the eyeball
What does the pigment epithelium absorb?
Excess light at the back of the retina and prevents the reflection of the light back inwards.
What does the reflection of light back inward of the pigment epithelium prevent?
image degradation.
What does the pigment epithelium nurture?
Rods and cones by supplying nutrients such as amino acids, ascorbic acid, and glucose.
What does the pigment epithelium remove?
The outer segment of rods and cones that are worn out by phagocytosis.
What serves as a physical barrier between neurosensory retina and substances in choroidal blood?
Pigment epithelium
How does the pigment epithelium maintain homeostasis?
Uses a delicate transport exchange system to maintain ionic homeostasis.
In a defective retinal pigment epithelium will result in what?
Night blindness
What is the clinical name for night blindness?
Nyctalopia
What is night blindness/ nyctalopia?
very difficult to see in low light environment and will result in insufficient adaptation of dark.
Tunnel vision and blindness are associated with what?
Defective retinal pigment apithelium
All rods and cones share some features which are what?
outer segment, inner segment , nucleus and synaptic body.
What do the outer segments of the rods and cones contain?
Photopigments/ Photoreceptors
What do the photopigments contain?
conjugated proteins containing opsin and a vitamin A derivative.
What is the name of the vitamin A derivative?
Retinal
Where are the photopigments of the outer segments inserted?
in the membranous discs as transmembrane proteins.
What are the membranous discs made up out of?
infolded membranes.
What are the membraneous disks lined with?
Photopigments that contain opsin and vitamin A derivative.
What does opsin activate?
G protein.
The outer segment interdigitates with what?
membrane extensions of cells in the retinal pigment epithelium.
What does the inner segment contain?
organelles similar to other somatic cells and have abundant mitochondria.
Why is abundant mitochondria necessary for inner segments of the rods and cones?
For high energy required by both rods and cones.
What is the synaptic body?
It connects with other cells in the neurosensory retina with bipolar and horizontal cells.
