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Rod photoreceptors
These neurons contain pigments which
are sensitive to low levels of light. Once
exposed to light, a chemical reaction
occurs inside the cell that causes the
neuron to fire an action potential which is
propagated to connecting neurons and
will eventually reach the visual centre of
the brain.
Choroidal blood vessels
The choroid consists of a dense network of
capillaries which deliver oxygen & nutrients via
the blood to the RPE and photoreceptors.
These vessels have a special perforated
structure which allow small molecules and
proteins to easily get in & out through pores.
Horizontal cells
These neurons help to collect
information from the photoreceptors
which is then passed on to the bipolar
cells. Their shape is not a ‘classical’
neuron shape but they are still able to
transmit electrical signals.
Cone photoreceptors
Like rod photoreceptors, these cells detect
light. There are three types of cone
photoreceptors, each of which are sensitive
to different wavelengths of light which
enables us to distinguish between different
colours.
Bipolar Cells
These neurons are important connectors in the retina,
forming synapses (a neuronal junction) with 4 different
types of neurons. They are connected to the
photoreceptors and the horizontal cells at one end and
to amacrine and ganglion cells at the other end. They
receive electrical signals from the photoreceptors and
horizontal cells which they then translate before passing
on to the amacrine & ganglion cells.
Retinal blood vessels
Due to the multilayered nature of the
retina, the retinal blood vessels need to
form three separate layers in order to
supply all the cells in the retina with
enough oxygen & nutrients to maintain
healthy vision.
Müller cells
These are non-neuronal glial cells which
support the surrounding neurons and
blood vessels by secreting factors that
help them survive and providing
architectural structure by stretching all
the way through the retina. Their endfeet
form close associations with blood vessels
and axons.
Retinal pigment epithelium (RPE)
These heavily pigmented epithelial cells help to
maintain the health of the overlying neurons in
the retina. The cells fit together in a hexagonal
shape and interdigitate with the underlying
neurons with long pigmented extensions.
Amacrine cells
These neurons help to transmit signals
from the bipolar cells to the ganglion
cells.
Ganglion cells
These neurons gather the information from the
amacrine and bipolar cells and pass this along a
very long axon that extends into the brain.
This work was produced by the UCL Institute
of Ophthalmology Knitting Group with help
from The Scientific Workshop and friends
including The Alresford WI & The Stroud
Green WI, Mary Barker, Ruth Stone, Sam
Black and Ellen Kelly.