Lecture 21- Eye Flashcards
Layer of the retina:
Adjacent to choroid
Derived from outer (thinner) layer of optic cup
Pigmented epithelium
Layer of the retina:
Outer segment consists of rhodopsin-containing lamellae
Inner segment consists of areas of rods and cones possessing mito., RER, golgi, and glycogen (metabolically active)
Inner and outer segments of rods and cones
Layer of the retina:
Area at junction of inner and outer segments of rods and cones and outer nuclear layer
Includes adherens junctions btw rods and cones and mueller cells.
External limiting membrane
Layer of the retina:
Cell bodies of rods and cones
1st order neurons
Outer nuclear layer
Layer of the retina:
Area of synapses btw axons and rods and cones and dendrites of bipolar neurons and horizontal cells
Outer plexiform layer
Layer of the retina:
Cell bodies of bipolar cells (2nd order neurons), horizontal cells, amacrine cells and mueller cells
Inner nuclear layer
Layer of the retina:
Area of synapses btw axons of bipolar cells and dendrites of ganglion cells
Inner plexiform layer
Layer of the retina:
Cell bodies of ganglion cells (3rd order neurons)
Ganglion cell layer
Layer of the retina:
Axons of ganglion cells
” a bundle of axons”
Optic nerve layer
Layer of the retina:
Terminations of mueller cell processes and their basement membrane
Internal limiting membrane
- Adjacent to choroid
- Synthesize melanin
- Apical processes surround and protect outer segments of rods and cones (photosensitive areas)
- phagocytose and degrade lamllae from rods and cones
- connected via tight junctions to form blood-retina barrier.
- esterify Vit A. Used in formation of photosensitive pigments.
Pigmented epithelial cells
Conducting neurons that synapse w/ rods and cones
Extend from outer plexiform to inner plexiform
Bipolar cells -2nd order neurons
Interneurons that interconnect rods and cones with each other and with bipolar cells
Extend in outer nuclear and inner nuclear layers of retina
Horizontal cells
Interneurons that connect ganglion cells and bipolar neurons
In inner nuclear layer
Amacrine cells
- neuroglial cells that extend throughout retina
- form external limiting membrane via zonula adherens btw mueller cells and rods and cones
- internal limiting membrane is formed by the basement membrane of these cells
Also in inner nuclear layer
Mueller cells
Conducting neurons whose axons form the fibers of the optic nerve
Extend from inner PLEXIFORM layer to optic nerve layers
Ganglion cells
Yellow region surrounding fovea
Highest visual acuity
Macula lutea
Depression of visual axis
Highest density of cone cells - sharpest visual acuity
Lacks rod cells and capillaries
Fovea centralis
Lacks photoreceptors
Point where ganglion cells turn into optic nerve
“Blind spot” of retina
Optic disc
Use rhodopsin as photopigment
Rods
Use 3 different kinds of iodopsins as photopigments
Cones
Rods and cones composed of 4 elements:
Spherule (rod) or pedicele(cone)
Cell body
Inner segment
Outer segment
Inner segment of rods and cones consist of:
Mito. And other organelles
Cell body of rods/cones consists of:
Nucleus and short axon
Outer segment of rod/cone consists of:
Modified cilium
Connected by a stalk to inner segment
Site of stacks of disks containing photoreceptors
Disks in rod cells
Disks detach from cell membrane and become free
Constantly renewed in rod cells
Older disks are phagocytosed by surrounding pigmented epithelial cells
Disks in cone cells:
Disks remain attached to cell membrane
Sensitive to low-light intensity.
Responsible for black and white vision.
Lamellae of outer segment are not continuous w/ plasmalemma.
Axons of up to 100 cells synapse w/ single bipolar cell-uses rhodopsin
Rods
Sensitive to high-intensity light.
Greater visual acuity.
Lamellae of outer segments are continuous w/ plasmalemma.
Each cell synapses w/ a single bipolar cell. -uses 3 kinds of iodopsins
Cones
Transmembrane glycoprotein
Consists of opsin and 11-cis-retinal (vit A derivative)
Rhodopsin
Disassembly of rhodopsin into opsin and retinal after light stimulation.
Bleaching
11-trans-retinal converted back to 11-cis-retinal.
11-cis-retinal transported back to photoreceptor.
Recombines w/ opsin = rhodopsin
Regeneration of photopigment.
3 parts of lens histology:
Capsule
Anterior epithelium
Lens nucleus
Insertion point for suspensory ligament
Glycoproteins and type IV collagen
Secreted by subcapsular epithelial cells
Capsule of lens
Simple cuboidal epithelium
Gives rise to cells that become “lens fibers”
Anterior epithelium of lens
Composed of lens cells that mature into fiber-like structures:
Devoid of nucleus and organelles and filled w/ crystalline proteins
Lens nucleus
3 elements of eyelid anatomy:
Anterior surface
Palpebral fascia
Palpebral conjunctiva
Covered w/ skin.
Glands of Zeiss (sebaceous glands asso/ w/ eyes).
Glands of moll (sweat glands-open into eyelash follicles)
Anterior surface of eyelid
Fibrous core of eyelids.
Meibomian glands -tarsal (sebaceous glands not asso. W/ hair follicles- opens on edge of eyelid. Secretion keeps norm tear film in eye)
Palpebral fascia
Stratified columnar or squamous epithelium w/ goblet cells
Lines inner surface of eyelids
Continuous w/ bulbar conjunctiva (covers eyeball)
Palpebral conjunctiva
