Lecture 22 Histology of the Eye II Flashcards
(43 cards)
Layers of the Retina
Pigmented epithelium Inner and outer segments of rods and cones External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Optic nerve layer Internal limiting membrane
Pigmented epithelium
Adjacent to choroid
Derived from outer (thinner) layer of the optic cup
Inner and outer segments of rods and cones
Outer segment consists of rhodopsin-containing lamellae
Inner segment consists of areas of rods and cones possessing mitochondria, RER, Golgi, and glycogen (metabolically active)
External limiting membrane
Area at junction of inner and outer segments of rods and cones and outer nuclear layer
Includes adherens junctions between rods and cones and Mueller cells.
Outer nuclear layer
Cell bodies of rods and cones (1st order neurons)
Outer plexiform layer
Area of synapses between axons of rods and cones and dendrites of bipolar neurons and horizontal cells.
Inner nuclear layer
Cell bodies of bipolar cells (2nd order neurons), horizontal cells, amacrine cells, and mueller cells
Inner plexiform layer
Area of synapses between axons of bipolar cells and dendrites of ganglion cells
Ganglion cell layer
Cell bodies of ganglion cells (3rd order neurons)
Optic nerve layer
Axons of ganglion cells
Internal limiting membrane
Terminations of mueller cell processes and their basement membrane
Cells of the Retina
Pigmented epithelial cells Bipolar cells Horizontal cells Amacrine cells Mueller cells Ganglion cells
Pigmented epithelial cells
Adjacent to choroid
Synthesize melanin
Apical processes surround & protect outer segments of rods & cones
Phagocytose & degrade lamellae from rods & cones
Connected via tight junctions to form blood-retina barrier
Esterify vit. A used in formation of photosensitive pigments
Bipolar cells
Conducting neurons that synapse with rods and cones
Horizontal cells
Interneurons that interconnect rods and cones with each other and with bipolar cells
Amacrine cells
Interneurons that connect ganglion cells and bipolar cells
Mueller cells
Neuroglial cells that extend throughout retina.
Form external limiting membrane via zonula adherens between mueller cells and rods and cones .
Internal limiting membrane is formed by the basement membrane of these cells
Ganglion cells
Conducting neurons whose axons form the fibers of the optic nerve
Macula lutea
Yellow region surrounding fovea
Highest visual acuity
Fovea centralis
Depression of visual axis
Highest density of cone cells
Lacks rod cells and capillaries
Optic disc
Lacks photoreceptors
Point where ganglion cells turn into optic nerve
“blind spot” of retina
Types of Photoreceptors
Rods
Cones
Rods
Use rhodopsin as photopigment
Sensitive to low-light intensity
Responsible for black-and-white vision
Lamellae of outer segment are not continuous with plasmalemma
Axons of up to 100 rods synapse with single bipolar cell
Cones
Use three different kinds of iodopsins as photopigment
Sensitive to high-intensity light
Greater visual acuity than rods
Lamellae of outer segment are continuous with plasmalemma
Each cone cell synapses with a single bipolar cell
