What are the functions of the eye?
1. regulation of amt of light entering eye 2. focusing of light to form an image 3. conversion of light to neural activity 4. processing of image before reaching the brain
Where does neural processing in the eye occur?
retina
What is the major refractive surface of the eye?
Corneal surface
What are the three layers of the eye?
cornea-sclera, choroid, retina
What is the structure and function of the cornea-sclera region of the eye?
dense irregular to regular collagenous tissue, it is protective and mechanically sound. Cornea is a distinct region from the sclera--can easily tell apart.
What is the structure and function of the choroid?
most central, highly vascularized, has pigment to prevent light scattering, has the IRIS and CILIARY BODY
What is the structure and function of the retinal region of the eye?
posterior, back of eye, transduces light to a neural signal
What are the three chambers of the eye?
anterior, posterior, vitreous
What is the structure anterior chamber?
marked by the lens, cornea and iris, contains AQUEOUS HUMOR
What is the structure and function of the posterior chamber?
defined by the lens, iris, zonule fibers, and ciliary body (where the ciliary body produces aqueous humor) has AQ humor
What is the structure and function of the vitreous chamber?
defined by the lens, zonule fibers, retina; has vitreous humor--gelatinous--similar to cartilage
Eye development results from the interaction of what embryonal layers and structure?
mesoderm, ectoderm, neural tube
The diencephalon gives rise to the.........which then folds to form the...........
1. optic vesicles; 2. optic cups
What do the layers of the optic cup become?
inner layer--retina (mesoderm), outer layer--pigmented retinal epithelium (ectoderm)
What do the optic vesicles induce?
lens
What does the lens induce?
cornea, from overlying ECTODERM
What do the mesoderm/neural crest cells form in eye development?
Associated tissues, vascular, muscle and CT
Where does retinal detachment occur in trauma?
In between inner and outer layers of formed from optic cup. Btw retina and pigmented retinal epithelium
What is the innermost neural layer?
retinal layer; neural retina, pigmented retinal epithelium
What is the middle vascular layer of the eye?
Choroid; has choroid, ciliary body, iris
What is the outermost fiber layer?
Cornea-sclera, has tendon ligament type tissue
The retinal pigment epithelium has what kind of epithelium?
simple cuboidal
List the 10 layers of the retina. Innermost to outermost.
1. Retinal pigmented epithelium 2. Photoreceptor rods and cones outer portions 3. outer limiting membrane 4. outer nuclear 5. outer synaptic(plexiform) 6. inner nuclear 7. inner synaptic 8. ganglion cell bodies 9. ganglion cell axons 10. inner limiting me
What are the components of the ganglion cell layer?
produces ganglia, becomes optic nerve
Components of the inner nuclear layer?
interneurons provide processing
Components of the outer nuclear layer?
innermost layer of interneurons, inner portion contains the photoreceptors: rods and cones
Label and identify
Label and id each layer.
What is the deepest layer of the neural retina?
rods and cones, photoreceptors
Rods and cones give rise to processes in what layers?
plexiform
Where are the nuclei of amacrine cells located? horizontal cells? bipolar cells?
INNER NUCLEAR LAYER
Where are mueller cells located?
ganglion layer
Where does signal transduction occur?
In the outer segments of photoreceptor cells
What is the function of mueller cells?
supportive, provide support for numerous neural elements
What is the function of the pigmented retinal epithelium?
1. provides nutrition for photoreceptors 2. absorbs light to prevent scattering 3. phagocytoses shed outer photoreceptor segments
What is the function of photoreceptors?
photo transduction of light to neural activity
What is the function of the interneurons?
neural processing
What is the function of the ganglion cells?
transmission of neural signal to the brain via the optic nerve
Fovea: location, function, characteristics
located at the back of the retina, in line with the visual axis; area of highest acuity; all cones; no blood vessels; cells spreading to form a pit
What is the optic disk?
BLIND SPOT, has no neural retina in area, origin of optic nerve
What is the ora serrata?
the anterior most layer of the neural retina, has only retinal pigmented epithelium, cannot transduce signal
All layers in the fovea are thinner except...
photoreceptor layer
What is the cribiform plate? Where is it located?
Dense CT with holes that axons of ganglion pass through, in the SCLERAL AREA. If ganglion are pressed up against it, can cause severe damage in glaucoma.
What produces the aqueous humor?
ciliary processes in the choroid layer
What is the iris? Function?
Diaphragm that controls the amount of light entering the eye. Constricts and dilates the pupil
Overproduction of aqueous humor leads to....
increased INTRAOCULAR PRESSURE
What is the choroid?
highly vascularized, pigmented loose CT
What is the function of the ciliary body?
regulates FINE FOCUS, by changing shape of lens. acts via the parasympathetically innervated CILIARY MUSCLES
What are the components of the ciliary body and their functions?
1. Ciliary process--secretes aqueous humor; 2. zonule fibers--fine fiber process connecting the ciliary body to the LENS
What is the function of the iris?
regulates amount of light entering eye by changing size of the pupil
What alters size of the pupil?
sympathetically innervated dilator pupillae muscle; parasympathetically innervated constrictor pupillae muscle
What type of muscle does the ciliary body have?
smooth
What is the ONLY layer of the retina located on the ciliary body?
pigmented epithelium
What is the flow of aqeuos humor?
created by cells on the ciliary process, goes through pupil to anterior chamber, drains through canal of schlemm
What is the canal of schlemm?
Drainage area for aqueous humor
What happens if he canal of schlemm is blocked?
anterior chamber won't drain, leads to compression and glaucoma
Where does the ciliary body extend from?
the ora serrata to the root of the iris
Ciliary body and processes are located in what chamber?
posterior
Where is the constrictor muscle of the pupil located?
on the iris, most medial, closest pupil
Where is the dilator muscle of the pupil located?
on the iris, lateral to the constrictor muscle
What is the only surface in the eye not covered by epithelium?
IRIS
What is the iris formed from?
anteriormost extension of the choroid
What are the epithelium layers of the iris?
double layered: outer nonpigmented layer becomes pigmented; inner pigment becomes myoepithelial
What is the dilator pupillae made up of?
myoepithelial cells
What is the constrictor pupillae made up of?
smooth muscle
What is the ciliary process made up of?
melanocytes and epithelium
What are the components of the corneal-sclera layer?
cornea, sclera, limbus, canal of schlemm
Sclera structure/function.
Dense opaque CT; covers posterior 5/6 of eye; insertion of extraocular muscles
Cornea structure/function
transparent avascular CT; primary refractive component of eye; covers anterior 1/6 of eye
What is the limbus?
area of transition from the sclera to cornea
What is the canal of schlemm?
Largest channel of trabecular meshwork; drains aqueous humor; blockage causes glaucoma. LOCATED IN THE LIMBUS
What are the 5 layers of the cornea?
1. corneal epithelium (strat squam non kerat corneal ep) 2. bowman's layer (membrane) 3. Stroma (dense regular CT) 4. Descemmet's layer (membrane) 5. Corneal endothelium ( simple squam)
The majority of the cornea is made up of what layer?
stroma dense regular CT
What is the function of the corneal endothelium?
maintains hydrostatic gradient in eye, cannot regenerate these cells, those that die are replaced by spreading of cells that remain
What is the function of Descemmet's membrane?
holds stroma to the endothelium
Structure/function of lens.
Biconvex transparent tissue, provides fine focus by altering shape by action of the ciliary muscle; has CT outercapsule (thick basement membrane), lined with epithelium that make long fibers that make up center of the lens
What are opafications of the lens?
CATARACTS
What are lens crystals?
highly packed proteins in lens that make it more transparent
Most common cause of cataracts?
oxidative stress
What do anterior epithelial cells of the lens differentiate into during development?
elongated fibers
What is the function of the eyelid>
Protect inner surface of eye
What is the structure of the eyelid?
outer surface--thin skin, epidermis; inner surface--thick skin, conjuctiva; made up of stratified columnar epithelium with goblet cells
What structures are found within the eyelid between the inner and outer surface?
tarsal plate (made of fibroelastic CT), orbicularis muscle, large sebaceous glands Meibobium; small sebaceous glands of eyelashes of Zeis, sweat glands of moll
Organization/function of lacrimal gland.
Secretes tears. Tubulo-alveolar serous gland. Large lumens, few ducts
Where in the eyelid are the meibobium glands located?
along tarsal plate, which gives something for the muscle to pull against
What layer of the retina are the cell bodies of the photoreceptors located?
outer neural