Histology Eye

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anterior chamber

how many cone cells are there?

6 to 7 million

cornea

tectorial membrane

What is the function of the sphincter pupillae?

Constricts the pupil (as light shines in)

What is the function of the sphincter pupillae?

Constricts the pupil (parasympathetic)

Function of the ciliary

Contain ciliary muscle Permits focusing on images of retina Attaches lens Secretes aqueous humour

Anterior compartment

Contains both the anterior and posterior chamber

Posterior compartment

Contains vitreous chamber

Ciliary epithelium

Double layer of low columnar epithelial cells covering the ciliary body

What is the function of trabecular meshwork?

Drains the aqueous humor into canal of schlemm

Is dry or wet macular degeneration most common

Dry macular degeneration

How is accommodation achieved

Due to elasticity of the lens in conjunction with action of ciliary muscle

________________ can be caused by excessive secretion of aqueous humor or impedance of the drainage of aqueous humor from the anterior chamber Vision loss due to _______________ is caused by damage to the __________ nerve.

Glaucoma can be caused by excessive secretion of aqueous humor or impedance of the drainage of aqueous humor from the anterior chamber

Common symptoms of glaucoma

Glaucoma haloes

Brown eyes have the ........... amount of pigment

Greatest

Optic disc histology

FIbres are myelinated and covered by meanings

Pigmented portion around the anterior portion of lens

Iris

The vascular tunic consists of?

Iris Ciliary Body Choroid

What is the middle vascular tunic composed of?

Iris ciliary body choroid

What are the layers in the middle vascular tunic (uvea)?

Iris, Ciliary Body, Choroid

Biconvex transparent structure, consisting of zonular fibers that hold in place

Lens

Fine

Lens Focus

Lens

Lens capsule Subcapsular Epithelium Lens fiber cells

What is shown here?

Macular degeneration of the eye

muller cells

Major supportive neuroglial cell of the retina

What can cause lens dislocation

Marfan's syndrome

What can scleritis indicate

May be first sign of autoimmune disease

Presbyopia

Means "eyes of the elders." A reduction in the elasticity of the lens, making accommodation for near objects difficult.

What glands do tarsal glands contain?

Meibomian glands

How do we get eye color?

Melanocytes of the iris Few lightly pigmented cells Blue color is reflected back from the black pigmented epithelium on posterior iris surface More melanin, darker the color that is reflected

Choroid

Middle layer that is more vascular, one part

Criteria for corneal donations

No Leukemia No lymphoma No systemic sepsis No previous radial keratotomy Negative serology for HepB/C, syphilis, HIV1/2 No history of IV drug use, prostitution, multiple sex partners, jail 18 hours post mortem or 24 with refrigeration

What does the fovea contain (and not contain)?

No blood vessels cone cells

Fibres before optic disc

Non myelinated afferent fibres

What is the histology of Conjunctiva

Non-keratinising stratified squamous epithelium, goblet scattered melanocytes

What blood vessels are located in the cornea

None

External Stratified Squamous Epithelium

Nonkeratinized Five or six cell layers 10% of corneal thickness Very thick basement membrane

Avascular Cornea contains

NO typical cells of connective tissue which is why corneas can be transplanted without extensive tissue typing

Cochlea

Name the entire structure?

Pancreas

Name the organ this tissue is a part of?

Fungiform papillae

Name the pictured structure?

4 functions of the aqueous humor.

Nourishes the lens Nourishes the Iris stroma Nourishes the Cornea Replaces vitreous fluid

Histology of choroid

Numerous blood vessels Melanocytes and melanin pigment

Vitreous

Occupies posterior compartment of the eye (between retina and posterior lens)

Anterior chamber

Occupies the space between the cornea and the iris

Immediate referral back to an ophthalmologist following PK or EK for what 4 things?

Ocular pain Scleral redness Corneal haze Mentions halos around lights

External Ear

Name this REGION?

Ear Ossicles

Name this collective structure?

Anterior Cavity

Name this space

Anterior Chamber

Name this specific area

Posterior Chamber

Name this specific area

Myopia vs Hyperopia

Near sighted vs Far sighted

Three types of cells in retina

Neurones Pigmented epithelial cells Neuronal support cells

Does conjunctivitis usually occur unilaterally

No - bilaterally

Mydriasis

Pupil dilatation that occurs without a cause. Can be due to trauma, drugs and raised ICP

Neural retina layers outer to inner layers (back to front)

RCL ELL ONL OPL INL IPL GL NFL ILL

Innermost layer of globe

RPE neural retina Ora serrata

Describe steps in radial keratotomy

Radial incisions penetrating deep into the stroma (anterior 2/3) starting at the Limbus towards the central cornea. Huge fad in the 80s and 90s.

Dilator pupillae muscle

Radially extended processes from the myoepithelial cells along the posterior side of the iris

Dilator Pupillae

Radially orientate Sympathetic innervation

Ciliary zonule

Radially oriented group of fibers that holds the lens in place, which inserts on both the lens capsule and the ciliary body

Function of Macula

Read, Distinguishing Fine Details in a Persons face

Outer plexiform layer

Region between the rod and cone cell layer and the bipolar cell layer. Contains fibers and synapses connecting the neurons in these two cellular layers

What is the function of the iris?

Regulate light input

Identify the 3 Intrinsic Muscles of the eye Circular Muscles vs Radial Muscles

Remember "Circular muscles constrict, radial muscles dilate"!!!!!

Function of optic nerve disc

Represents beginning of optic nerve and point where atonal ganglion cells together

Function of cone cells

Responsible for colour vision and function best in relatively bright light

What is another name for the inner tunic?

Retina

Photoreceptive tunic

Retina -10 layers -posterior (photosensitive) -anterior: Ciliary body/ posterior part of iris

Surface ectoderm

What is 1?

Optic Stalk: Neuroepithelium

What is 2?

Lens vesicle

What is 3?

Neural retina

What is 4?

Pigmented epithelium

What is 5?

Trabecular meshwork

What is this?

3 sources of nutrition for the cornea

Tear film Lateral diffusion from the limbus vasculature Aqueous humor in the anterior chamber

Choroid

Vascularized, loose connective tissue -Fibroblast, macrophage, lymphocyte, mast cell, plasma cell, melanocyte, elastic fiber -Choriocapillary Layer

what is contained in the fovea

a large concentration of cones not rods

Define: Ectomesenchyme.

a mass of tissue consisting of neurocrest cells present in the early formation of an embryo. It eventually forms the hard and soft tissues of the neck and cranium.

what causes green eyes

a mutation in the melanin structure

AMD, age-related macular degeneration

accumulation of amyloid material in the inner side of Bruch's membrane , which forms unwanted deposits called drusen.

bowmans layer

acellular, doesnt regenerate

what do muller cells do

act as support cells

what is accommodation?

adjustment of the lens depending on if one is looking far or close.

Pigment Epithelium

layer 1, columnar cell -basal nucleus: transport nutrient from choroidal blood to outer layers of retina, remove waste from sensory retina, phagocytosis of shed photoreceptor disks, synthesis BL of Bruch's membrane, synthesis of photopigment rhodopsin, controls trans retinol into retinal

inner limiting membrane

layer 10

Nerve fibers - axons of ganglion cells

layer 9

Where is the corneal endothelium located?

layer of the cornea that sits on the basement membrane (descemet's membrane)

contracted ciliary muscle

loose zonular fibers thick lens near vision

What kind of cells makes up the pigmented layer?

low columnar cells with basal nuclei

What is the border of the fovea?

macula lutea

sphincter pupillae muscle

made of concentric smooth muscle bundles around pupil parasympathetic innervation constricts pupil

dilator pupillae muscle

made of myoepithelial cells of inner later sympathetic innervation dilates pupil

the fovea only has ___ photoreceptors

cone

macula lutea and fovea centralis

cones are concentrated here

what is the path of light through transparent structures

cornea, anterior chamber, lens, vitreous body

keratocytes

maintain precise spacing between collagen bundles of stroma only cells of CT in cornea

Trabecular Meshwork

maintains pressure by regulating outflow

the ___ of the cornea is important because it prevents the aqueous humor produced by the ciliary body from getting into the stroma

endothelium

Path of Aqueous humor

enter posterior chamber, slide over lens, enter anterior chamber, drain into trabecular meshwork

spleen

entire structure?

crystalline lens

epithelial cells grow into long, closely-packed transparent fibers, *hexagonal prisms parallel to lens surface* that refract light. anterior lens vesicle = thin sheet of low cuboidal cells (subcapsular epithelium) - capsule = elastic and collagenous membrane to which the suspensory (zonule) fibers attach

crystalline lens

corneal ___ has a lot of wound healing properties

epithelium

the ___ can secrete aqueous humor

epithelium of the ciliary body

When the ciliary muscle contracts, what direction are the choroid and ciliary body pulled?

forward

what happens to the lens when the ciliary body contracts

makes the lens thicker

ora serrata

meeting of the photosensitive and non-photosensitive retinal cells

Ora serrate

meeting of the photosensitive and non-photosensitive retinal cells demarcation for anterior/posterior portion of retina

what is in the inner epi of the ciliary processes

melanin

what causes a differentiation between brown and blue eyes

melanin levels in melanocytes of the eye

what are rod cells responsible for?

night vision

Ora Serrata

non photo sensitive anterior part of retina

ciliary processes inner layer

non pigmented produces *aqueous humor* continuous with sensory layer of retina

outer layer

non-keratinized stratified squamous epithelium

what is the function of the choroid?

nourish the retina

What is the function of Choriocapillaris?

nourishes a significant part of the retina • nourishes the retina pigment and photoreceptors

Outer nuclear layer

nuclei of photoreceptor

what can you find in the external nuclear layer

nuclei of rod and cone cell

What is the function of the middle vascular tunic?

nutrients

• Where do the first signs of dentin formation occur?

o At the tips of the future cusps (cervical loop)

• What does the enamel knot secrete, and what is its effect on the underlying epithelium? What happens to the enamel knot after the cusp is formed?

o BMP4 in the papilla induces the enamel knot. o Enamel knot secretes more molecules to the IDE to become ameloblasts and make enamel. o Enamel knot sets the tip of the cusp and then undergoes apoptosis. In molars, they secrete p21 to stop proliferation and then induce ameloblasts.

• When are the successional permanent teeth initiated?

o Between 20 weeks in utero and 10 months after birth. (the entire primary dentition is started between 6-8 weeks in utero.)

• When are the permanent molars initiated?

o Between 20 weeks in utero and 5 years.

Glaucoma

optic disc atrophy with characteristics cupping usually with increase intra-ocular pressure and progressive peripheral visual field loss

the central artery of the retina passes through the ___

optic nerve

what is the "blind spot"?

optic nerve = no photoreceptors

describe the anterior stroma of the iris and state which layer of the choroid it corresponds to

pigmented cells corresponds to the vessel layer of the choroid

Describe the outer layer of the retina

pigmented double epithelium (this is the case for the entirety of the retina)

ocular melanomas:

pigmented malignant tumors that can cause systemic metastasis

describe the dilator muscle of the iris and state which layer of the choroid it corresponds to

radially arranged pigmented myoepithelial cells corresponds to the pigment epithelium of the retina

What is the function membraneous disk of rhod cells?

receives light signals and bleaches photopigment rhodopsin in a reversible manner (photosensitive cells inserted into the membraneous disks)

Glands of Zeis

sebaceous glands of eyelashes

Meibomian glands

sebaceous glands of the eyelid that secrete meibom, which protects the eye from becoming dry

Meibomian glands

sebaceous glands of the eyelid that secrete meibom, which protects the eye from becoming dry, prevents evaporation of tears

Ciliary Bodies

secrete aqueous humor

tarsal (meibomian) glands

secrete onto eyelash region for lubrication

tubuloacinar glands

secrete tears into conjunctiva recess between orbit and inner eyelid

NT release (inner hair cells)

sound-elicited movements of the basilar membrane excite neurotransmitter release from the inner hair cells onto the processes of bipolar neurons, whose cell bodies are located in the spiral ganglion. This ganglion is located within the cochlea, inside its bony central axis, the modiolus. Axons from spiral ganglion neurons project in the VIIIth nerve to the brainstem.

What layer do you need for rods and cones to work?

retinal pigment layer

The pigmented layer Isomerize and regenerate _____ used by rods and cones

retinoids

What pigment proteins do rods and cones use

rhodopsin and iodopsin

Ciliary body

ring + crown = gross structures best seen in an axial view (are circular structures)

which photoreceptors are more sensitive

rods

what is the structure of the photoreceptor cell outer segments

rods cones

Photoreceptor layer

rods and Cones

RCL

rods and cones layer: outer and inner segments of photoreceptor cells

what do the pigment epithelia regulate growth of

rods and cones turnover and rhodopsin

the ___ is composed of fibrous cells and is opaque

sclera

what is the cornea continuous with

sclera

where do the extraocular mm. attach

sclera

what is the outer fibrous tunic composed of?

sclera Cornea

what are the three layers of the eye?

sclera choroid retina

What are the layers in the outer fibrous tunic?

sclera and cornea

what are the three tunics of the eye

sclera, choroid, retina

Inner plexiform layer

synaptic region between bipolar and ganglion cells

what drains the Aq. humor

the canal of schlemm

what is the ora serrata

the circular edge of the photosensitive part of the retina

what is found in the nerve fiber layer

axons of ganglion cells

inner limiting membrane

b.m. of muller cells

What is the overall function of bowman's layer?

barrier to trauma and bacterial invasion

what forms a capsule around the lens

basement membrane

Lens Capsule

basement membrane -Collagen IV, glycoproteins, heparin sulfate

Lens Capsule

basement membrane -Collagen IV, glycoproteins, heparin sulfate - surrounds entire lens - really a basement membrane

What layer of the cornea is descemet's membrane?

basement membrane (thick)

What is the apical domain?

basement membrane epithelium that faces the inside of the eye

Descemet's membrane

basement membrane for inner cell layer

Bowman's membrane

basement membrane for outer epithelium

Descemet's Membrane

basement membrane of endothelial cells

What is the role of elasticity of the lens in accommodation?

bears about 70 ridges (ciliary processes) where suspensory ligaments pass to the lens

where is visual acuity high in high light

fovea

a shallow indentation in the back of the retina important for sharp vision:

fovea centralis

what is the small pit?

foveola in center of fovea

what is the function of rods?

function in intensity discrimination

what is the function of cones?

function in wavelength discrimination and visual acuity

What Synapse with bipolar cells in the internal layer?

ganglion cells

the bipolar cells synapse with the dendrites of the ____

ganglion cells

Ganglion cell layer

ganglion cells that form optic nerve fiber layer

ganglion layer cell bodies of ganglion cells

uveitis:

inflammation of the uvea

filensin

intermediate filament that composes beaded filaments in lens that help with lens transparency

phakinin

intermediate filament that composes beaded filaments in lens that help with lens transparency

vascular layer

iris and cilliary body

corneal endothelium

has occluding zonules. blood aqueous layer. pumps fluid out of stroma/regulates ions. doesn't regenerate -next to decemet's membrane

corneal endothelium

has occluding zonules. blood aqueous layer. pumps fluid out of stroma/regulates ions. doesnt regenerate

Anterior Surface

have cubodial cells

How are the lens fibers of the lens substance of the lens held together? why is this important?

held together by transparenting substance that permits some movement between lens fibers during accommodation

How is the corneal epithelium attached?

hemidesmosomes

Choroid

highly vascularized, heavily pigmented loose connective tissue abundant *melanocytes* block light suprachoroidal lamina choriocapillary lamina Bruch's membrane

Choroid

highly vascularized, heavily pigmented loose connective tissue abundant *melanocytes* block light 1) vessel layer (loose CT, arteries + veins + melanocytes) 2) choriocapillaries (layer fen caps, extends anteriorly to ora serrata, *nourishes outer half of retina* which lays upon it) 3) Bruch's membrane (innermost layer, basement membrane) trauma = retinal detachment

Decemet's membrane

homologous structure with collagen fibrils

Decemet's membrane

homologous structure with collagen fibrils like a thick basal lamina that regenerates- lays down corneal endothelium thickened b.m. of endothelium of cornea

The Primary epithelial band forms a _________shape in both the _______ &________.

horseshoe, maxilla, mandible.

Common pathology associated with cones

Colour blindness

Pingueculum

Common type of Conjunctiva degeneration

Corneal abrasion

Scratch on the eye's cornea

tectorial membrane

Nictitating membrane

3rd eyelid of some animals; medial conjuctival fold

Vestibular Membrane

cornea

hair cells

monocyte

posterior cavity

posterior chamber

sclera

venule

vestibular membrane

Which nerve innervates the Pupillary Dilator muscles? Which nerve innervates the Pupillary Constrictor muscles?

(1) the sympathetic nerves innervate the pupillary dilator muscles; and (2) the parasympathetic nerve fibers (from CN III) innervate the pupillary constrictor (sphincter) muscles as well as the ciliary apparatus for lens accommodation.

NFL

(optic) nerve fiber layer processes of ganglion cells leading from the retina to the brain

Define Apoptosis

(programmed cell death) of cells in the vestibular lamina form a cleft, which is the VESTIBULE.

Cochlear Implants

- 15,000 have been implanted worldwide. - Up to 24 electrodes, at different positions along the scala tympani, just beneath the basilar membrane. - Device used to deconstruct sound and activate different electrodes in response to different frequencies - threaded through scala tympani through round window

Describe the ciliary muscle of the ciliary body and state which layer of the choroid it corresponds to

- 3 layers of smooth muscle -elastic fibers -pigmented cells corresponds to the epichoroid layer of the choroid

conjuctiva

Tectorial membrane

- overlies cochlear hair cells, which normally press against it - anchored on one end, just lying on cilia on the other - so sound makes it shear/slide against the 4 rows of hair cells! - (basilar membrane is bouncy, attached to a ligament)

conjuctiva

- At corneal margins, *epithelium of anterior sclera (bulbar) is continuous w/ mucous membrane that lines eyelids (palpebral)* - strat squamous (at corneal margin) - strat cuboidal w/ mucous goblet cells (secretions part of tear fluid) - underlying stroma very loose, rests on cushion of intraorbital fat (permits free rotation of eye) - seals off orbit from outside world stratified low columnar epithelium covers anterior sclera and inner surface of the eyelid contains small number of mucous secreting cells Limbus = white bulbar - white with red blood vessels forineal- pinkish hue over white tarsal- red backside of eyelid

Cochlear implant - Xray

- Device used to deconstruct sound and activate different electrodes in response to different frequencies. - Up to 24 electrodes, at different positions along scala tympani, just beneath the basilar membrane. - Bypasses damaged hair cells to directly stimulate 8th nerve afferents. - Can damage residual hair cells, so only used for profound hearing impairment.

Accessory structures of the eye

- Eye lids - Lacrimal gland - Conjunctiva

semicircular canals

- Head rotation is detected by hair cells lining the crista ampullaris in ampulla chamber of these structures (*angular rotation*)

Myopia

- If the eye is too long, *in-focus image formed in front of retina*, image formed on retina is out of focus - *corrected w/ negative (reducing) lens* - "nearsightedness"

Hypermetropia

- If the eye is too short, then *in-focus image plane = behind the eye*, image formed on the retina is out of focus - corrected with *positive (magnifying) lens* - "farsightedness"

Identify the cells of the neural retina

- Neurons: ganglion, bipolar, horizontal, Amacrine, Rods and cones (photoreceptors) and integrating neurons - Pigmented epithelial cells - Neuron support cells - Müller cells

otoacoustic emissions

- Newborns are routinely tested for hearing impairment using a device inserted into the ear canal that contains a small speaker and sensitive microphone. - If everything is functioning properly, a test sound pulse causes the outer hair cells to contract in response, which in turn elicits fluid movement in the organ of Corti that vibrates the oval window, ossicles and tympanic membrane in reverse, *producing a tiny "echo" sound* picked up by the mic! - In adults, spontaneous vibratory movements of the outer hair cells can sometimes produce otoacoustic emissions loud enough to be audible to others

Function of the retina

- Photoreception - Convert light into neural processes so brain can use it for visual recognition

inner hair cells release transmitter

- Sound-elicited movements of the basilar membrane excite neurotransmitter release from the inner hair cells onto the processes of bipolar neurons, whose cell bodies are located in the spiral ganglion - This ganglion is located within the cochlea, inside its bony central axis, the modiolus - labels in the left picture indicate different portions of this continuous, spiral-shaped ganglion - Axons emanating from the spiral ganglion neurons project in the VIIIth nerve to the brainstem.

Function of the choroid

- Supplies nutrients and O2 to all layers of the eye - Absorbs light to prevents light scattering within eye

Auricle (Pinna)

- Thin skin with hair follicles, sweat glands and sebaceous glands - keratinized stratified squamous epi - supported by elastic cartilage

Vitreous function

- Transmits light - Supports the lens - Holds the retina in place - Contributes to intra-ocular pressure

Cataracts

- With age, osmotic balance of the lens fibers (cells) may change, causing them to become less transparent - *visual image becomes hazy, color perception diminished* - more common blue-eyed, lot of time in bright sun - can be corrected surgically, by removal of cloudy lens and replacement with a plastic one

accomodation

- active *contraction of ciliary muscle leads to relaxation of lens* (becomes more round), and enables the eye to focus on close objects - pupils also get smaller, and eyes look together

Presbyopia

- age-related decrease in the ability to focus on near objects - lens loses elasticity w/ age - can't become round to focus close - during 50's - get reading glasses

Tarsal glands

- aka Meibomian glands of eyelid - large, sebaceous-like - drain via ducts at tip of eyelid - secrete oily substance that floats on surface of serous tear fluid produced by lacrimal gland - inflammation = chalazion

scala media

- aka cochlear duct - membranous "tunnel within a tunnel" - attached at two sides along its length to the cochlea (osseous labyrinth), creating three compartments.

Middle Ear

- amplifies sound energy - due to lever action + space - from low to high resistance system (need to get oval window moving, because cochlea is full of fluid) - harder to move!

Cornea!

- anterior basement membrane = Bowman's - posterior basement membrane = Descemet's

Anterior retinal tunic

- anterior border = ora serrata (goes back to 2 soccer ball layers) - forms epithelium that covers ciliary body - RPE and superficial layer (non light sensitive), ciliary body folds attach to lens - also create fluid, taken up by retinal epithelial cells, pumped into posterior chamber 1) attachment for lens 2) produce aqeuous humor (similar to CSF) - tunic continues to tip of iris, heads back down

Iris anterior surface

- anterior surface has no epithelial covering - design flaw! - porous covering of fibroblasts - beneath, loose CT + pigments - blue eyes = less pigment, green, then brown has most

vitreous chamber

- area between lens and retina

anterior chamber

- between inner surface of cornea (anteriorly) - and lens, iris + base of ciliary body (posteriorly) - trabecular network surrounds it circumferentially

anterior chamber

- between inner surface of cornea (anteriorly) - and lens, iris + base of ciliary body (posteriorly) - trabecular network surrounds it circumferentially -both chambers filled with aqueous humor and are interconnected through the pupil

adventitia

4 - name

Eustachian (auditory) tube

- cartilagenous walls lined w/ *pseudostrat ciliated columnar epithelium* - connects middle ear to nasopharynx - allows *equalization of middle ear pressure* w/ atmospheric pressure - normally collapsed, opens during swallowing or yawning - infections can spread from pharynx to middle ear via this structure - the resp epithelial lining does a pretty good job of preventing bacteria entry, mucous sheet + cilia sent to back of throat

Age related macular degeneration

- common retinal problem of aging eye, leading cause of blindness - macular + fovea compromised due to *degeneration of underlying (RPE)* - allows fluid to leak behind fovea. In these areas (drusen) *cones of fovea die, causing central visual loss*

pars iridica retinae

- continuation of ciliary retina to tip of iris at pupillary opening - two pigmented layers - anterior *myoepithelial layer forms dilator pupillae*

otoconia

- crystals of calcium carbonate in otolith organs (saccule + utricle) - make the otolithic membrane heavier than the structures and fluids surrounding it. Thus, when the head tilts, gravity causes the membrane to shift relative to the sensory epithelium. This acts to bend the stereocilia of the hair cells, inducing a receptor potential that alters their transmitter release. A similar shift of the otolithic membrane also occurs when the head undergoes linear acceleration, such as in an elevator.

Ear Drum

- described by hippocrates in 450 bc - handle of malleus - punctured w/ tube during infection

central retinal artery / vein

- enter globe within optic nerve (through lamina cribosa) - pass through to interior of globe, then run laterally + spread over inner retinal surface - smaller branches penetrate retina, nourishing its innermost half w/ a capillary plexus

Pars ciliaris retinae

- epithelial (non photo sensitive) part of retina - anterior - double epithelium, covers ciliary body + posterior iris - produces aqueous humor

bulbar conjunctiva

- epithelium that covers anterior eye

flipped images

- eye forms *upside down and backwards image* - objects at top of visual field are focused on inferior retina and reversed left-to-right

Cornea

- eye's principal lens, avascular - *inner half nourished by diffusion from aqueous humor within anterior chamber* - *outer half nourished by tear fluid* - has five histological layers: 1) surface epithelium 2) *Bowman's* membrane (epithelial basement membrane) 3) body (90% of thickness) 4) *Descemet's* membrane (endothelial basement membrane) 5) endothelium (low cuboidal)

Cornea

sclera

- fibrous CT, opaque, merges w/ cornea - thickens at scleral spur - exterior surface: covering of very thin loose fascia, *episcleral (Tenon's) fascia* - Anteriorly, has epithelial covering continuous w/ corneal epithelium + bulbar conjunctiva

posterior chamber

- formed by iris (anterior) - lens and zonule (posteriorly) - and ciliary process (peripherally)

Body of cornea

- formed by many lamellae of collagen fibrils arranged at right angles to eachother w/ intervening fibroblasts - allows cornea to be *rigid + transparent*, and to refract light - orthogonal layers

What is the function of the Iris

- forms a diaphragm in front of the lens and regulates the amount of light entering the eye

what is the structure of the fovea centralis?

- funnel-shaped depression at posterior pole in optical axis -macula lutea - small pit - fovea

Retinitis pigmentosa

- genetic defect - Phagocytised discs accumulate w/out being digested, RPE degenerates - *night blindness* as rods go - next, *tunnel vision* w/ only fovea spared - Eventually, cones also destroyed = *complete blindness* (40 y/o) - black pigment in peripheral retina, thinned blood vessels at optic nerve head

corneoscleral limbus

- globe formed by spheres of unequal diameter (sclera larger, cornea smaller) - point of intersection of spheres = circular zone around the eye

tip links mechanism

- hair cell bundle consists of a group of stereocilia (large microvilli filled w/ actin filaments) - When stimulus bends stereocilia in one direction, non-selective cation channels open in tips of stereocilia --> depolarization of hair cell, increased transmitter release. - Bending the other way: hyperpol, decreased steady-state transmitter release. - In mature auditory system, hair cells release transmitter in a continuously graded manner w/ memb potential - Such transmitter release w/out APs unusual in nervous system. first neurons in auditory system to display APs = bipolar spiral ganglion neurons (cochlea) carry info from hair cells to brainstem. = examples of mechanically-gated ion channels. Tip links connecting apical ends of stereocilia act to open the channels when stretched (right figures.) Due to the ionic composition of the endolymph, *K enters rather than exiting cell when channels open*

cochlea

- hollow bony spiral, that turns around a central bony column (modiolus) - converts sound pressure waves generated by the ossicles into electrical activity in spiral ganglion neurons - consists of a spiral *fluid-filled tube* that everywhere along its length has 3 components, visible in cross-section: 1) scala vestibuli 2) scala media 3) scala tympani - basilar membrane, which divides the scala media from the scala tympani, is the location of the organ of Corti, where sensory transduction occurs

anterior ciliary arteries

- penetrate the sclera just posterior to the corneoscleral limbus - provide blood to the ciliary body and iris

Neural Retinal specializations

- inner layer of retinal epithelium, post 2/3rds (CNS tissue) - light passes thru all 10 layers to reach RPE! 1) RPE 2-5) photoreceptor layer 8) ganglion cell layer (large multipolar, process + fire APs, output to 9 + CN II) 9) nerve fiber layer (ganglion cell axons) 10) inner limiting membrane (basment membrane connects it to vitreous body)

tip links

- join steriocilia into bundles - mechanically pull open K channels - because this is *faster than other senses*!

Body of lens

- large #s of individual lens fibers - highly specialized cells that develop from anterior epithelium - extend all the way to posterior surface

External auditory meatus

- lined w/ thin skin (keratinized strat squamous) - contains hair follicles, sebaceous glands + *ceruminous glands* - inside lining is cartilage externally, then becomes bone internally

Glaucoma

- may be caused by: 1) Blockage of the trabecular meshwork by particles from iris (no surface epithelium!!!) 2) Blockage of the t.m. by physical collapse of the iris - *normal eye pressure (IOP) = 10-20mmHg* - open angle: iridocorneal angle normal - closed angle: caused by trauma, iris + cornea pulled together by scarring, collapse of meshwork

Glaucoma

eyelid

- meibomian: posterior, oily secretion - anterior eyelid - modified apocrine glands (Moll = near eyelashes, Zeis)

Rod + cone layer of retina

- membranes here contain rhodopsin

Ceruminous glands

- modified apocrine sweat glands - secrete waxy material called cerumen - hairs + sticky wax help prevent foreign particles from penetrating deeply into ear - moves slowly out, so it removes particles

tonotopy of basilar membrane

- movement of the stapes against the oval window produces pressure waves that travel along the basilar membrane, causing it to move in a shearing fashion against the tectorial membrane, stimulating the hair cell stereocilia - structure of the 35mm long basilar membrane is such that each frequency produces its maximum displacement at a different location along its length (tonotopy) *distinguish b/t sounds* - Because each afferent neuron fiber innervates a single locus along the basilar membrane, it responds best to one particular frequency - group of active auditory axons in the VIIIth nerve informs the brain of the exact frequency composition of any complex sound - each area has different neurons!

Dilator pupillae muscle

- myoepithelial fibers arranged radially around iris - sympathetic innervation - by shortening, increase diameter of pupil

Retinal Development

- neural tube closure, two vesicles connected by stalks (volleyball) - collapse on themselves, form double layered cup 1) inner layer = retina (filled w/ vitreous humor, attaches to inner eye lining - impact here can detach) 2) outer layer = retinal pigment epithelium (RPE) - hyaloid artery degenerates, fragments float around in vitreous - epithelium folds back on itself at tip of the Iris

Crista ampullaris

- neuroepithelium, at base of semicirc canals - inertial lag of fluid in chambers, presses against bendable pupula, causes stereocilia to bend, depolarization, NT release, APs in primary terminals of vestibular ganglion - stereocilia + hair cells!

Emmetropia

- neutral, relaxed state of normal eye - cornea plus the flattened lens act to form an image of distant objects exactly in the plane of retina - When the lens thickens, it becomes stronger, eye can then focus on close-by objects

retinal detachment

- no CT between two retinal layers, vulnerable to detachment (two apical surfaces! nothing holds them together, b/c basement membrane is OUTSIDE) - can separate between the two layers, or both can pull off of the choroid (cause problems for oxygenation of retina)

fovea

- on TEMPORAL side, lateral to entrance of optic nerve! - only photoreceptors present (cones), bipolar cells lie outside, axons must run laterally to them - specialized area of retina (thin, no inner retinal layers) - increases visual acuity!

dark rooms

- only deep red light - keep you dark adapted even though you can see - so you can see in the dark! but aren't literally just in the dark - rods fully active, you remain "dark adapted" - like fighter pilots

Rods

- only one type(broad range of detection) - *active only in low light* - extremely sensitive, can detect a single photon - more in peripheral retina (peripheral vision is color-blind!)

Rods

- only one type(broad range of detection) - *active only in low light* - extremely sensitive, can detect a single photon - more in peripheral retina (peripheral vision is color-blind!) -sensitive to low light -rhodospin -120 million rod cells in human retina

Color blindness

- opsin proteins determine wavelength of light photoreceptors can see - different *opsin genes on X chromosome* - males more suscpectible to color vision defects (only have one copy of each gene) - *loss of green opsin most common* (can't distinguish between red and green) - *Ishihara plates* distinguish

Papillodema

- optic nerve bulges into posterior chamber of eye - sclera + dura are continuous, so high ICP will cause increased pressure around optic nerve - vein pops, artery stays (thicker walls) - fluid into EC spaces, optic disk, normally concave, *becomes convex*

Photoreceptors

- outermost retinal neurons - interacts directly w/ light - outer segment (*nonmotile cilia w/ infoldings*) = discs w/ rhodopsin protein, bound to light-sensitive Vit-A derivative - absorption of light by this complex --> (*phototransduction*) - stacked membranes increase chance that photon will be detected

RPE

- photoreceptor disks are in stacks, constantly renewed, shift - phagocytoses worn-out outer-segment disks - reisomerizes photopigment - provides general metabolic support to the PR - synthesizes melanin to absorb stray light - makes active retinal, converts Vit-A to retinal

Iris

- pigment granules - posterior surface has double layered epithelium (part of inner tunic) - anterior surface has no epithelium

fovea 1

- retinal region specialized for high res, color vision - innermost *retinal layers present, but displaced to sides* - fewer layers to pass through, light scattered less, increases image sharpness (higher primates) - avascular zone

lamina cribrosa

- round perforated zone in the posterior pole of eye - corresponds to blind spot - where ganglion cell axons, central retinal artery and central retinal vein enter eye

otolith organs

- saccule and utricle, located in dilated regions of inner ear *vestibule*, near ampullae of semicirc canals - Internally lined by* simple cuboidal* epithelium, each has small region of specialized epithelium, *macula - contains hair cells* - stereocilia embedded in gelatinous membrane covered with otoconia

Lamina cribosa!

- sclera continuous w/ optic nerve sheath (dura)

Spiral ganglion

- shaped like a spiral because it follows/inntervates the ribbon-like basilar membrane - is a continuous strip of neurons - gets bigger and bigger as it moves down the cochlea (more and more axons)

posterior ciliary arteries

- short: penetrate sclera near the optic nerve - long: penetrate each side of globe - provide blood to the middle (uveal) tunic (nourishes the avascular portion of overlying *retina* by diffusion)

Inner (conjunctival) eyelid surface

- simple --> strat cuboidal - may contain goblet cells - bacterial infection here = "pink eye"

Retinal pigment epithelium (RPE)

- simple cuboidal - retina rests here - regenerates bleached photopigments - phagocytoses degenerated discs

Eyelid external surface

- skin, hair follicles, sebaceous + sweat glands

Canal of Schlemm

- small tunnel lying just under the corneo-scleral limbus (scleral specialization) - running completely around the eye, forming a ring-like structure. - functions to drain the fluid (aqueous humor) produced in the eye

Endolymph K gradient

- stria vascularis of scala media makes endolymph --> reversed K gradient across apical hair cell surface - high K outside of stereocilia! unusual! - channels *make K enter cells --> depolarize, NT release* - not APs, release NT onto afferent endings of spiral ganglion

Lens epithelium

- subcapsular - simple cuboidal - covers only anterior portion of lens

basilar membrane

- supports organ of corti

Lens capsule

- surrounds entire lens - really a basement membrane

Macula lutea

- surrounds fovea centralis

Zonule fibers

- suspensory ligament of lens - group of colorless, refractile fibers between ciliary process + lens

cochlear hair cells

- tectorial membrane (TM) that overlies the hair cells is seen in the upper left exposure of the entire cochlea - well-organized rows of hair cell stereocilia that normally press against the tectorial membrane are revealed when the membrane is pulled aside (upper right figure) - one row of inner hair cells (what you hear with) and three rows of outer hair cells (not for hearing!)

For accomodation, what happens in close vision?

- the ciliary muscle contracts - ciliary body connected to zonular fibers becomes closer to the lens -Tension reduces and lens rounds up

For accomodation, what happens in close vision?

- the ciliary muscle contracts - ciliary body connected to zonular fibers moves closer to the lens -Tension reduces and lens rounds up

Inner hair cells of organ of corti

- the sensory transducers for hearing - The organ of Corti functions as the sound receptor, lies on basilar membrane, composed of hair + supporting cells - hair cells project stereocilia against tectorial membrane (TM) - There are two types, the inner and outer hair cells. The inner hair cells transduce sound into changes in membrane potential and thus into changes in hair cell transmitter release - basilar membrane = ribbon!

outer hair cells

- under efferent control from brain, *physically contract* when electrically stimulated - very specialized neurons, unusual! - Changes in length enhances sensitivity of inner hair cells by altering the sound-elicited shearing force experienced by inner hair cell stereocilia against TM!

stria vascularis

- unusual in being an epithelium with capillaries - makes/ maintains the special ionic composition of endolymph in the scala media that bathes the hair cells

stria vascularis

- unusual in being an epithelium with capillaries - specialized epithelium maintains the special ionic composition of the endolymph in the scala media that bathes the hair cells.

vortex veins

- venous return of eye - perforate sclera - one for each quadrant of eye

Causes of conjunctivitis

- viral - bacterial - Allergic

fixation

- when you look directly at an object

scleral veins

- where aqueous fluid drains after moving through meshwork into canal of Schlemm

Organ of corti - diagram

- where sensory transduction appears - 3 part chamber 1) upper - vestibuli 2) middle = media 3) lower = tympani - stapes vibrates, sends vibration in - round window required for fluid vibration, moves out when oval window moves in, allows for movement of perilymph fluid

What are the five layers of the cornea?

-An external stratified squamous epithelium -An anterior limiting membrane (Bowman's membrane)-Basement membrane of the stratified epithelium -Stroma -Posterior limiting membrane (Descemet's membrane)-Basement membrane of the endothelium -Inner simple squamous endothelium

What causes a cataract?

-High glucose levels causes sorbitol to accumulate in the lens fibers -Excess of sorbitol reduces solubility of crystallins leading to opacity

What structures sit within the uveal layer

-Iris - Calgary body - choroid

What are the functions of lacrimal glands?

-Tubulo-acinar serous glands -Produce tear film -Tears drain into nasal cavity

during cell elongation of lens development

-cells produce crystallins -after reaching 7-10 mm cell nuclei and organelles regress - remaining elongated, crystallin filled cytoplasm becomes *lens fibers*

Optic disc

-central artery branches enter -central veins exit

Optic disc

-central artery branches enter -central veins exit -site on posterior retina where axons converge and exit eye as optic nerve

describe the lens substance of the lens

-composed of lens fibers -cells regenerated throughout life -cells lose nuclei and other organelles; become filled with proteins = CRYSTALLINS -zonule (suspensory ligament)

Posterior surface of iris

-controlled by SNS -Dilator muscle

5 layers of the cornea

-corneal epithelium -bowman's membrane -stroma -Descemet's membrane -corneal endothelial

Iris

-covers lens -pupil -anterior surface -posterior surface -spinchter muscle

Subcapsular Epithelium

-cuboidal epithelium -anterior surface -elongate into fiber cells

Canal of Schlemm

-drains aqueous humor from anterior chamber of the eye

What is a meibomian secretion?

-fatty secretion which lubricates the eyelid -prevents tear spillage onto the cheek

Lens Fiber cell

-from epithelial cell -loose nuclei and organelles -contain primary crystallins -fiber cell differentiation (scatters)

Describe the capsule of the lens

-homogenous membrane -contains collagenous fibrils - elastic d/t arrangement of fibrils

Limbus

-interface between sclera and cornea -vascularized -trabecular meshwork -canal of schlemm

Sclera

-maintain size and shape of eye -nonvascular -anteriorly covered by Bulbar Conjunctiva -Posteriorly covered by bulbar sheath

Retina (2 layers)

-neural retina -pigmented layer (outer layer) fragile attachment between 2 layers in developed eye both layers derived from two cell layers of the embryonic optic cup

Choriocapillary Layer

-nutrition of retina -fenestrated capillaries -bruch's membrane -darkly stained

Canal of Schlemm

-resorbs the aqueous humor; located at the limbus - small tunnel lying just under the corneo-scleral limbus (scleral specialization) - running completely around the eye, forming a ring-like structure. - functions to drain the fluid (aqueous humor) produced in the eye

Describe the constrictor (sphincter) muscle of the iris and state which layer of the choroid it corresponds to

-smooth muscle -lies around pupillary margin -circularly arranged Corresponds to the epichoroid layer of the choroid

Corneal Epithelium

-stratisfied squamous -contigous with bulbar conjunctival epithelium

Corneal Epithelium

-stratisfied squamous -contigous with bulbar conjunctival epithelium -outer layer of cornea, contains free nerve endings

What are the functions of the retinal pigment epithelium?

-supply nutrients to photoreceptors - phagocytosis of outer segments -prevention of internal light segments -converts retinal to retinol

For accomodation, what happens in distant vision?

-the ciliary muscle relaxes -ciliary body with zonular fibers become further to the lens -tension increases and lens narrows

For accomodation, what happens in distant vision?

-the ciliary muscle relaxes -ciliary body with zonular fibers moves away from the lens -tension increases and lens flattens

retinal detachment

-trauma and physical shock can cause separation of 2 layers of retina pigmented epithelium and neural retina - no CT between two retinal layers, vulnerable to detachment (two apical surfaces! nothing holds them together, b/c basement membrane is OUTSIDE) - can separate between the two layers, or both can pull off of the choroid (cause problems for oxygenation of retina)

Limbus

-vascularized -trabecular meshwork -canal of schlemm

Draw a diagram of the bell stage enamel organ. Portray it at high enough power to show the cell shapes of ODE, IDE, stellate reticulum and stratum intermedium.

...

Draw a diagram of the enamel organ in late cap stage, showing how histodifferentiation has created outer dental epithelium, inner dental epithelium and stellate reticulum When does this occur?

...

What major event occurs at late bell stage?

...

When are the incisors initiated in the enamel knot?

...

Cochlear duct

Optic nerve II

anterior chamber

arteriole

ciliary body

cortex

eosinophil

hyaline cartilage

mucosa

neural layer

platelets

red pulp

respiratory bronchiole

scala vestibuli

sclera

tunica intima

bronchiole

1 - columnar cuboidal lined

alveoli

1 - singular

spiral organ

1 - structure

Inner Ear

1) bony labyrinth (hollowed out cavity) - semicircular canals, vestibule, cochlea 2) membranous labyrinth (suspended within bony labyrinth, contains auditory + vestibular sensory structures)

Vestibular apparatus

1) otolith organs (static head position + linear acceleration) *- saccule: vertical - utricle: horizontal* 2) semicircular canals specialized for detecting head turns - oriented in three orthogonal planes. lower right: device for selectively stimulating them

Cones

1) red 2) green 3) blue - packed at high densities within retina - provide high resolution, fine-grained image - daylight! - more in central retina (fovea) - rods absent from foveal pit

Choroid

1) vessel layer (loose CT, arteries + veins + melanocytes) 2) choriocapillaries (layer fen caps, extends anteriorly to ora serrata, *nourishes outer half of retina* which lays upon it) 3) Bruch's membrane (innermost layer, basement membrane) trauma = retinal detachment

What are the layers of the posterior chamber (with aqueous humor)?

1- Zonular fibers 2- Basil Lamina 3- Ciliary lamina 4- ciliary channel 5- Pigmented Ciliary Epithelium 6- Basal Lamina 7- fenestrated capillaries

What are the 2 layers of the sclera?

1- episcleral tissue 2- substania propria (corneal stroma)

What are the 5 layers of the cornea?

1-Corneal Epithelium 2-Bowman's Layer 3-Corneal Stroma (Substania propia) 4-Descemet's Membrane 5-Corneal Endothelium

What are the layers of the posterior chamber (with aqueous humor_?

1-Zonular fibers 2-Basil Lamina 3-Ciliary lamina 4-ciliary channel 5-Pigmented 6-Ciliary Epithelium 7-Basal Lamina 7-fenestrated capillaries

What are the inner segments of the rod cell?

1-basal body 2-centriole

What are the 3 layers of the choroid?

1-epichoroid: loose layer of cells, elastic fibers 2- vessel layer: veins and arteries 3- bruch's membrane: basement membrane and elastic fibers

What are the outer segments of the rod cell?

1-membraneous disc 2-modified cilium

7 pharmaceutical treatments for glaucoma

1. B1 blocker - less aq. humor produced 2. alpha 2 agonist - less aq. humor produced 3. carbonic anhydrase antagonist- less aq. humor produced 4. alpha 1 agonist - constricts ciliary vessels 5. muscarinic agonist - constricts sphincter and ciliary muscle 6. Ach esterase inhibitor - constricts sphincter and ciliary muscle 7. Prostaglandins (PGF2a) - constricts sphincter and ciliary muscle

what does the choroid contain?

1. Bruch's membrane 2. Choroidal stroma 3. Choriocapillaris

What are properties of the ciliary muscle/body?

1. Double epithelium: Outer pigmented layer + Inner ciliary epithelium 2. Ciliary Proccess: Fenestrated capillaries + Attachment of lens 3. Ciliary muscle: Contraction facilitates accommodation of lens attached to ciliary body

What two things does the iris have that the choroid and ciliary body not have?

1. Epithelium a. continuous with corneal endothelium b. simple squamous/cuboidal 2. General stroma -CT, highly vascular -pigmented cells

What causes a cataract? what leads to opacity of the lens?

1. High glucose levels (diabetes) - glucose changes into sorbitol • Sorbitol accumulates in the lens fibers, and this is what cross-links the crystalline 2. Excess of sorbitol reduces solubility of crystallins leading to opacity

Late Cap Stage

1. Histodifferentiation occurs (cells look different from each other) 2. Enamel organ differentiates into stellate reticulum, outer epithelium & inner epithelium. ---Inner dental epithelium gets taller ---Middle cells are getting dispersed by GAGs (ground substance); they spread the cells apart and make them loose. -They become stellate reticulum (star web) that are spread apart, but held together by desmosomes. ---- Outer epithelium is still cuboidal. ----This is all still epithelium, so there are no blood vessels present. Any nourishment comes from the basement membrane.

The neural retina is attached to the RPE by what five parameters?

1. Interdigitation b/w photoreceptor outer segments and the microvilli of RPE cells. 2. Mucopolysaccharide glue in the subretinal space 3. An extra mucus condensation at the tip of the cone outer segments 4. Viscosity of the vitreous body 5. Water flux across retina from vitreous to choroidal vessels driven by ion pumping of the RPE

What are the layers in the middle vascular tunic (uvea)?

1. Iris 2. Ciliary Body 3. Choroid

Functions of Retinal Pigment Epithelium

1. Make melanin and store it in melanosomes 2. Help with retinal attachment with interdigitation b/w microvilli of the RPE cells and the outer segments of the photoreceptors 3. Pump ions to drive the water flux across the retina from the vitreous into the choroidal vessels

What are the layers of the retina

1. Neural retina 2. Retinal pigment epithelium

What are the layers in the inner tunic?

1. Pigmented Epithelium 2. Neural Retina

3 parameters that must be appraised for success of LASIK

1. Pupil size must cover the flap margins otherwise complain of halos 2. No tear film dysfunction 3. No connective tissue system disease 4. A sufficiently thick stroma to support the new contoured stromal surface on which the flap lays.

Cataract surgery steps

1. Small incision through cornea 2. Remove anterior capsule and epithelial cells 3. Lamellar dissection with saline injection 4. Fragmentation and suck out the lens fragments by phacoemulsification but leave the sulcus of the capsule at the equator intact 5. Polish posterior capsule 6. Insert foldable intraocular lens

Explain the Cap Stage

1. The epithelium becomes a cap sitting on a ball of condensed ectomesenchyme --> enamel organ. a. Still separated from the ectomesenchyme by basement membrane. (surrounded entirely by basal lamina) 2. The ball pushes its way into the cap and is now the dental papilla -->dental -->pulp 3. Ectomesenchyme around the dental organ and papilla is the dental follicle (sac) --> periodontal ligament, cementum & alveolar bone --Note, there's not really a specific border between the papilla & follicle; just generalized outer area is the follicle, inner ball is the papilla. 4. All three together form the tooth germ. 5. The successional dental lamina will be the permanent tooth.

what are the three most important layers of the choroid?

1. bruch's membrane 2. choroidal stroma 3. choriocapillaris

10 things you do when you see a peaked pupil

1. call ophthalmology 2. cut nothing 3. clean nothing 4. no topical antibiotics 5. no topical anesthetics 6. apply no pressure to eye 7. cover eye with styrofoam cup 8. patient must be NPO 9. patient sits still 10. Can't bend over, lay down, lift anything, perform valsalva activity

What are the components of the lens?

1. capsule 2. lens substance 3. epithelium

What are the contents of the vitreous body?

1. clear semisolid gel that is 99% water 2. has a small population of hyalocytes which produce some collagen and hyaluronic acid 3. hyaloid membrane 4. hyaloid canal

What features of the cornea enhance light transmission through it?

1. curvature 2. lens

What are the characteristics of the zonule (suspensory ligament) of the lens substance of the lens?

1. passes from the ciliary processes of the ciliary body --> equator of lens 2. thin collagenous fibrils: continuous with the lens capsule

What are three important characteristics of corneal endothelium?

1. permeable to air 2. regulates hydration of stroma 3. vital to transparency of stroma

what are the layers of the retina (beginning at the pigment epithelium)

1. pigment epithelium 2. rods and cones 3. outer limiting membrane 4. outer nuclear layer 5. outer plexiform layer 6. inner nuclear (bipolar layer 7. inner plexiform layer 8. ganglion cell layer 9. nerve fiber layer 10. inner limiting membrane

other than the choroid and ciliary body being pulled forward, what happens when the ciliary muscle contracts?

1. relaxes tension on the zonule 2. lens becomes more convex d/t its own elasticity 3. refractive power of the lens is increased

What are the layers in the outer fibrous tunic?

1. sclera 2. cornea

Describe the pathway of the aqueous humore.

1. secreted by 2 layers of epithelial cells and blood vessels 2. diffuses through the posterior chamber 3. moves through the pupil 4. Meanders through the anterior chamber 5. moves across the resistance of the trabecular meshwork 6. Exits in the canal of Schlemm to venous flow via bulk flow

Describe the epithelium of the lens

1. simple cuboidal 2. present on anterior surface - rests on membrane 3. epithelial cells transform into lens fibers at equator of lens

5 glaucoma treatment options

1. slow down blood flow in ciliary body 2. Induce parasympathetic miosis and accommodation 3. Slow down aqueous humor production by epithelial cells 4. Laser trabeculectomy 5. Insert filtration tube that carries humor from anterior chamber to venous spaces in bulbar subconjuctival space

Visual processing of Light (steps)

1.Light activates pigment molecules in the photoreceptors -loss of chromophore 2. activation of pigment molecules reduces the cytoplasmic concentration of *cGMP* 3. reduction in cGMP concentration closes cGMP-gated Na+ channels photoreceptor cell membrane then hyperpolarizes 4. membrane hyper polarization decreases glutamate release at the synapse 5. decreased glutamate secretion is detected by the bipolar neuron - bipolar neuron initiates electrical pulse that goes to brain

Explain the bud stage

1.Simple spherical swelling of the dental lamina --Epithelial cells have little change in shape/function. 2. Supporting ectomesenchyme surrounds the bud & condenses. 3. The basement membrane separates the epithelium and the mesenchyme. (simple cuboidal cells) 4. The lamina will always arch toward the tongue 5. around the tooth bud because it will form the future dental papilla! (which will be the pulp and then the dentin) ---The tooth bud will be the enamel.

Auditory CN VIII

how many cell layers in the retina

the outer segment of the photoreceptors is recycled every ___ days

how many rod cells are there?

120 million

Round Window of Vestibule

How many subtypes of neurons are in the neural retina?

Scala vestibuli

alveolar duct

leukocytes

medulla

neutrophil

pigmented layer

posterior cavity

posterior chamber

retina

scala media

scala tympani

tunica externa

white pulp

tunica intima

2 - layer

ciliary process

2 - lines

alveoli

2 - plural

Cochlear duct

Scala tympani

choroid

erthrocytes

lymphocyte

respiratory bronchiole

retina

scala tympani

sclera

tunica media

hyaline cartilage

3 - layer type

pseudostratified columnar epithelium

3 - layer type

Color 色彩 Contour 輪廓 Cupping

3 Cs of the optic nerve

What is the overall plan or layout of the eye?

3 chambers: anterior, posterior, vitreous 3 layers: sclera, choroid, retina Outer fibrous tunic: protection Middle vascular tunic: nutrients Inner tunic: retina

Basilar Membrane

adipocytes

basilar membrane

iris

lens

sclera

pseudostratified columnar epithelium

5 - layer type

what layers do bipolar cells stretch across

5-7

pupil

Transducin

A g-protein to which opsin is coupled

Accommodation

A process which permits focusing on near and far objects by changing the curvature of the lens

Ciliary processes

A series of about 75 radial ridges extending from the surface of the ciliary body

Management of Ulcerative Keratitis

Immediate referral as delay may cause loss of sight

Aniridia

Absence of the iris usually involving both eyes

3 events of the near synkinesis（連帶運動） reflex

Accommodation (Parasympathetic CNII) Convergence (CNIII on medial recti muscles) Miosis (Parasympathetic CNIII)瞳孔縮小

Lens function

Accommodation - Permits focusing on near and far objects by changing curvature

What is the function of the ciliary muscle?

Accomodation of the lens

Activation of parasympathetic fibers to _________________ (circular) muscles of the iris causes them to contract, decreasing pupil size.

Activation of parasympathetic fibers to sphincter pupillae (circular) muscles of the iris causes them to contract, decreasing pupil size.

Simple Squamous Endothelium

Active in protein synthesis-maintain basement membrane Pump sodium ions into anterior chamber Largely responsible for maintaining a state of hydration within the cornea -Maximum transparency -Optimal light refraction

Function of Conjunctiva

Acts as a protective layer Allows eye lids to move freely over eye

Scleral venous sinus (canal of Schlemm)

Adjacent larger space from which fluid is drained into the aqueous and episcleral veins of the sclera

In Aus, what is the most common causes of cataracts

Ageing lens

7 cellular causes of leukocoria

Aggregation of crystallins Irregularly of type IV collagen in the anterior and/or posterior capsule Irregularly of anterior lens epithelial cells Irregular interdigitation of the lens fibers Organells retained within the lens fibers as they differentiate at the equator from lens epithelial cells Increased interstitial fluid between the lens fibers Irregular shape of the lens fibers

7 cellular causes of leukocoria白瞳症（Ｘ）

What is the function of the cornea

Allows entry of light Principle mechanism for focusing images on refine

Function of ciliary processes

Anchors lens in place Forms aqueous humour

What is the irregular, discontinuous layer of fibroblasts and melanocytes?

Anterior chamber of the iris

List and describe the layers of the cornea

Anterior corneal epithelium (StSq, microvilli), Bowman's membrane (collagen fibers, no cells), corneal stroma (regular arrangement of tropocollagen type I, III, V, VI), Descemet's membrane, corneal endothelium (SiSq)

Ora serrata

Anterior edge of the retina

What is the function of the ciliary body?

Anterior expansion of the choroid at the level of the lens Loose connective tissue, elastic fibers, melanocytes Ciliary muscle - Changes the shape of the lens

Where is the cornea located

Anterior part of cornea-scleral layer

How does cornea meet its metabolic needs

Aqueous humour and environmental O2

Posterior chamber

Area between the iris and lens

Unequal curves along the surface of the eye will cause what condition?

Astigmatism

What properties of the cornea?

Avascular and twice the refractive index as the lens

Eye

Complex and highly developed photosensitive organ that analyzes the form, intensity, and color of light reflected from objects, providing the sense of sight.

Ectomesenchyme underneath the primary epithelial band starts _______.

Condensing

Amoebic Keratitis

Condition in which the eye's cornea becomes inflamed

What cells are most concentrated in the fovea?

Cone cells

Bowmans Membrane

Basement membrane of stratified squamous epithelium

Descements Membrane

Basement membrane of the endothelium Posterior surface of the stroma Fine interwoven collagen fibers

Posterior limiting membrane (Descemet's membrane)

Basement membrane of the endothelium of the cornea

Anterior limiting membrane (Bowman's membrane)

Basement membrane of the stratified epithelium of the cornea

How sound-induced vibrations move the hair cell stereocilia back and forth

Because the tectorial membrane (purple) is anchored only at one end, the hair cell stereocilia embedded in it are rocked back and forth as the basilar membrane on which they reside moves up and down in response to sound

What happens to the fibres in the lens with cataracts

Become irregular and raggered

Lens histology

Capsule - collagen IV Subscapular epithelium - single layer of cuboidal epithelium Lens fibres - Epithelial cells

WHat is the function of the microvilli in the corneal epithelium?

Capture the tear film to protect the eye (captures particles)

Clinical Correlate Cataract

Cataract: loss of transparency of the lens or lens capsule

This condition results from a loss of transparency of the lens or lens capsule.

Cataract: loss of transparency of the lens or lens capsule. Bluriness of Vision

Posterior chamber

Between the iris, ciliary processes, zonular attachments, and lens

Lens

Biconvex transparent structure held in place by the zonular fibers

amacrine cells and horizontal cells

Both of the above spread horizontally and integrate signals from photoreceptors

This membrane separates the Choiroid from the Retina

Bruch's Membrane

Age-related macular degeneration

Causes blindness in the center of the visual field. Degeneration of the macula lutea

Scleral pathology

Congenital thinning of the scleral seen in Marian's syndrome and osteogenesis imperfecta

Outer limiting layer

Consists of a series of junctional complexes between the photo receptors and the Müeller cells

Connecting stalk

Constrictive inner segment of the rod cell. A modified cilium arising from a basal body

where does the cornea receive innervation

CN 5.1

Retinitis Pigmentosa

Can cause night blindness Progressive loss of rods

Flow of aqueous humor

Canal and trabeculae drain into episcleral venous plexus

3 Cs of the optic nerve

Color Contour Cupping

What consists of the middle layer? (Uvea)

Choroid Ciliary body Iris

Middle layer of the globe

Choroid Ciliary body with processes Iris

What aspect of the ciliary body and iris are orthologs to the Epichorid (the loose layer made of elastic fibers and pigmented cells in the choroid)

Ciliary Body: Ciliary muscle (3 layers of smooth muscle, elastic fibers, pigmented cells) Iris: Constrictor (sphincter) muscle (smooth muscle, lies around pupillary margin, circularly arranged)

Histology slide Section of ciliary processes showing their double layer of pigmented and nonpigmented epithelial cells. What fluid is produced by the Ciliary Processes?

Ciliary Processes produce Aqueous Humor ***Outer non-pigmented layer (facing posterior chamber) transports a protein poor plasma from fenestrated capillaries into posterior chamber of eyeforms aqueous humor (similar in ionic composition to plasma but contains less than 0.1%protein -compared with 7% protein in plasma)

Ciliary

Ciliary body + ciliary muscles + ciliary processes

What is similar in the ciliary body and the iris to bruch's membrane of the choroid?

Ciliary body: Bruch's membrane (continues as 2 layers) Iris: NOTHING

What is similar in the ciliary body and Iris to the epichoroid of the chorid layer?

Ciliary body: Cilary muscle Iris: Constrictor (sphincter) muscle

What structures of the ciliary body and the iris are similar to the nervous retina of the choroid?

Ciliary body: ciliary epithelium Iris: posterior pigmented epithelium

What is similar in the ciliary body and the iris to the pigment epithelium of the retina?

Ciliary body: pigment epithelium (heavily pigmented simple cuboidal cells) Iris: Dilator muscle

What is similar in the ciliary body and the iris to the vessel layer of the choroid?

Ciliary body: vascular layer Iris: Anterior stroma

Longitudinal portion

Ciliary muscle group inserts in choroid stroma

circular portion

Ciliary muscle group oriented concentrically (having common center like circles)

radial portion

Ciliary muscle group radiates outward and inserts in fibrous part of ciliary body

Ciliary Body

Ciliary muscle: controls lens curvature Ciliary Processes: -zonules emerge -actively transport plasma into posterior chamber

Ciliary Body

Ciliary muscle: controls lens curvature anterior, thickened extension of choroid layer concentric ring of smooth muscle around the opening in which the lens is suspended main part of ciliary body is continuous with the *choroid* Ciliary Processes: -zonules emerge -actively transport plasma into posterior chamber includes ciliary muscle/body ciliary processes zonular fibers

Eye at rest or gazing at a distant object

Ciliary muscles are at rest Lens kept stretched by zonules

Eye focusing on close object

Ciliary muscles contract causing forward displacement of choroid and ciliary body Lens round up

Which muscles control accommodation?

Ciliary muscles control accomodation of the lens to focus on near objects

What is the function of the zonular fibers?

Ciliary process attaches the lens

Which structures produce the aqueous humor?

Ciliary processes produce the aqueous humor, which fills the anterior and posterior chambers.

Aqueous Humor

Cilliary process

Iris

Circular colour membrane surrounding the pupil

Zonular fibers

Circular system of fibers that holds the lens in place. Extend from the lens into the ciliary body

Constrictor pupillae

Circumferentially oriented Parasympathetic innervation

Aqueous humor

Clear fluid of the posterior and anterior chambers

This type of Glaucoma results when the aqueous humor is unable to reach the trabecular meshwork because an inflammatory process or genetic malformation blocks fluid access to the meshwork drain. Iridocorneal angle

Closed Angle Glaucome

Cornea

Coarse Focus

What type of Collagen is the Lens encased in?

Collagen Type IV

What is found in the Stroma?

Collagen lamellae at angle to one another; Transparency depends on arrangement and affinity to water

Actions of the Ciliary Muscles and their effects on the shape of the lens of the eyes. Contraction vs Relaxation Fat lens vs Flat lens

Contraction causes the lens to BULGE Relaxation causes the lens to flatten.

Optic nerve

Convergence of the ganglion cells' axons. Leaves the eye and passes to the brain

Anterior 1/6th of eye Colorless, transparent and completely avascular

Cornea

Refractile media of eye

Cornea Anterior/Posterior aqueous chamber Lens Vitreous Humor Space

What structures sit within the corneal scleral l layer

Cornea Scleral Limbus

Trace the pathway of light in order for vision to take place

Cornea, anterior chamber, pupil, lens, viterous body, retina

What are the five layers of the cornea?

Corneal epithelium Bowman's layer Stroma Descemet's membrane Corneal endothelium

3 layers of the eye

Corneoscleral layer Uveal layer Retinal layer

What are lens made up of?

Crystalline protein

Keratocytes

Cytoplasmic extensions of flattened fibroblast-like cells between the collagen lamellae of the stroma

What is the function of the dilator Pupillae?

Dialates the pupil (sympathetic)

Two muscles of the iris

Dilator pupillae Constrictor pupillae

What does the iris separate

Divides anterior compartment into anterior and posterior chambers

What are properties of the cilliary muscle?

Double epithelium: 1-Outer pigmented layer 2-Inner ciliary epithelium Fenestrated capillaries: Attachment of lens Ciliary muscle: Contraction facilitates accommodation of lens attached to ciliary body

What is a determining factor of stroma when looking at EM images?

Dark nuclei

Keratoconus

Degenerative disorder of eye in which structural changes causes it to thin and change to conical shape

Tarsus

Dense fibroelastic plate of connective tissue adjacent to the conjunctiva. Provides support for the other tissues of the eyelids.

Scleral Histology

Dense fibrous vascular tissue

Risk factors of cataract

Diabetes Steroid therapy Poor nutrition Smoking

Embryological origin of the Lens?

Ectoderm

Optic cups

Embryonic origin of the eye

Corneoscleral junction (limbus)

Encircles the cornea, a transitional area where the transparent stroma merges with the opaque sclera

What are the layers of the choroid?

Epichoroid Vessel Layer Bruch's membrane Pigment epithelium of retina Nervous retina

What tissue permits movement of the eye?

Episcleral tissue: loose connective tissue that connects to dense connective tissue - makes the the sclera

Describe the structures incorporated into the ciliary body

Epithelium (pigmented, non-pigmented), stroma (loose CT), ciliary muscles (ciliaris)

Name the derivatives of the retina within the ciliary body and iris

Epithelium covering the ciliary becomes part of the retina Nonpigmented body or cilliary process becomes the neuroepithelium

What is the function of Choriocapillaris?

Exchange metabolic nutrients between retina pigment and photoreceptors

How to reattach the retina

Expandable gas in the vitreous body Silicone oil in the vitreous body Scleral buckle with laser burns Administer mucagen

Fibrous Tunic (SCoLE)

External Layer -sclera -limbus -Cornea

5 layers of cornea

Eyes Bold Standout Dangerous Exotic - Epithelium (Ep) - Bowman's membrane (BM) - Stroma (SP) - Descemet's membrane (DM) - Endothelium (En)

Zonules

Fibres emerge from ciliary processes and insert into the lens

Vitreous chamber

Filled with vitreous fluid Takes up most of the space in the eyeball

Complaints of retinal detachment

Floaters Fireworks Field defect

Vitreous pathology

Floaters (small darks spots in visual field)

Closed angle glaucoma

Fluid builds up behind iris against cornea impeding flow through trabecular meshwork

bipolar neurons

Form synaptic connections with neurons in all layers of the retina

Stroma (substantia propria)

Formed of approx 60 layers of parallel collagen bundles. Between the collagen lamellae are keratocytes.

Membranous disks

Found within the outer rod-shaped segment of the rod cell

The Aqueous Humor goes from ________________ directly into the venous system.

From anterior chamber, aqueous humor goes from Canal of Schlemm directly into the venous system Aqueous humor provides nutrients and oxygen for the lens and the cornea

What is the opacity of the sclera due to?

High water content

What is the opacity of the sclera due to?

High water content/ high collagen content??

What is the fovea centralis known for?

Highest visual acuity

Describe lens fibers

Highly differentiated epithelial cells No nuclei No organelles Cytoplasm of crystallins Avascular

Lens fibers

Highly elongated ;) and appear as thin, flattened structures that make up the lens

What are lens fibers?

Highly elongated, thin flattened structures

Iris histology

Highly vascular tissue Pigmented stromal cells Anterior surface = fibroblasts and melanocytes Posterior surface = smooth pigmented epithelium

Function of zonules

Hold lens together

Colobomas

Hole in one of the structures of the eye such as iris, retina, choroid

Causes of retinal detachment

Idiopathic Secondary due to intraocular pathology

Bipolar neurons

Intermediate layer of the neural retina. Connects to the rod and cone cells and the ganglion cells

Ganglion cells

Internal layer of the neural retina. Synapse with the bipolar cells through their dendrites and send out axons that converge to form the optic nerve

Lens vesicles

Invaginated ectoderm that leads to the formation of the lens

Phototransdution

Involves a cascade of changes in the cells triggered when light hits and activates retinal and is basically similar in both rod and cone cells

Neovascularisation in damage cornea

In-growth of blood vessels into avascular cornea. Secondary to anterior segment pathology

Presbyopia

Inability to focus up close due to loss of elasticity in lens "long sightedness"

Glaucoma

Increased intraocular pressure

Styes

Infections near an opening of the tarsal gland ducts, generally caused by staphylococcus aureus. Most common in infants.

Ulcerative Keratitis

Inflammation of the cornea termed Keratitis

Receptor

Information about the external world is conveyed to the CNS from sensory these

The response of a rod photoreceptor cell to light

Inhibition of neurotransmitter release!!!! after binding of rhodopsin and closure of Na+ channels

Neural retina

Inner layer of the retina. Contains the neurons and photo receptors

Retina

Inner most lining of the posterior compartment of the eye

Choriocapillary lamina

Inner region of the suprachoroidal lamina that is richer than the outer layer in microvasculature

Retina

Inner sensory layer, which consists of an outer pigmented epithelium, and an inner retina proper

Endothelium

Inner simple squamous epithelium of the cornea

Function of scleral

Insertion of extra ocular muscles for voluntary eye movement Protective and supportive role

What is the function of rod photoreceptors?

Intensity discrimination

Describe the sclera and explain its opacity

It is the reflection of the amount of collagen that is in there tough capsule that keeps the eye into shape

Conjutiva

Joins eyeball with the eyelid

stroma

Keratinocytes, collagen, chondroitin sulfate orthogonally (right angles) arranged collagen bundles collagen types 1 and 5 precise spacing between bundles maintained by *keratocytes*

Stroma

Keratinocytes, collagen, chondroitni sulfate

Anterior chamber

Label 1

Basal Lamina

Label 1

Centriole

Label 1

Choroid

Label 1

Lens

Label 1

Retinal pigment layer

Label 1

Vitrous humor

Label 1

Zonular fibers

Label 1

Basal Body

Label 2

Iris

Label 2

Lens

Label 2

Photoreceptors - inner and outer segments

Label 2

Pupil

Label 2

Retina

Label 2

Retinal pigmented epithelium

Label 2

Canal of Schlemm

Label 3

Choroid

Label 3

Cornea

Label 3

Modified Cilium

Label 3

Neural Retina

Label 3

Posterior chamber

Label 3

ciliary channel

Label 3

outer limiting layer

Label 3

Iris

Label 4

Membraneous disk

Label 4

Outer nuclear layer

Label 4

Sclera

Label 4

pigmented ciliary epithelium

Label 4

sclera

Label 4

Cornea

Label 5

basal lamina

Label 5

canal of schlemm

Label 5

outer plexiform layer

Label 5

cornea

Label 6

fenestrated capillaries

Label 6

inner nuclear layer

Label 6

Choroid plexus

Label 7

inner plexiform

Label 7

Trabecular meshwork

Label 8

ganglion cell layer

Layer 8

Lens fibers contain _____________ (fibers or cells that have lost their nuclei and organelles). ______________ are among the longest-lived proteins in the body; they are formed in utero and persist for the life of the individual. Lens also keeps growing throughout life. What type of Collagen Fibers are found in the Lens?

Lens fibers contain crystallins (fibers or cells that have lost their nuclei and organelles). Crystallins are among the longest-lived proteins in the body; they are formed in utero and persist for the life of the individual. Lens also keeps growing throughout life

what are cone cells responisble for?

Less sensitive to low light than rod cells Specialized for color vision in bright light Three types of cone cells Variations of iodopsin pigment Red, blue or green regions of the visible spectrum

Medical term for white pupil.

Leukocoria

Vitreous chamber

Lies behind the lens and its zonular attachments and is surrounded by the retina

Choroid

Lies between the retina and sclera Highly vascular and heavily pigmented layer of the eye

light route in eye summary

Light passes through the neural layer to the photoreceptor cells. Signals generated by these cells pass back through the neural layer where they exit via ganglion cell axons and pass into the optic nerve.

What is the Area where stroma merges with the sclera?

Limbus

Where are the Stem cells for stratified epithelium are concentrated?

Limbus

1. Pigment epithelium 2. Photoreceptor layer 3. Outer limiting membrane 4. Outer nuclear layer 5. Outer plexiform layer 6. Inner nuclear layer 7. Inner plexiform layer 8. Ganglion cells 9. Optic nerve fiber 10. Inner limiting membrane

List the 10 layers of the retina

- activated in dim light - cannot sense colors - contain more rhodopsin due to their longer outer segment

List the characteristics of Rods

- posterior aspect of cornea (exposed to aqueous humor) - simple squamous epithelium

List the characteristics of the corneal endothelium

a basement membrane (thick)

List the characteristics of the descemet's membrane

1. Posterior chamber 2. Pupillary apperture 3. anterior chamber 4. trabecular network 5. canal of Schlemm 6. aqueous veins 7. episcleral veins

List the path of aqueous humor.

Lacrimal apparatus

Location where eye fluid accumulates

Rods

Long slender bipolar cells - Consist of inner and outer segments

Vernal conjunctivitis

Long term chronic swelling of outer lining of eye

Histology of ciliary body

Loose connective tissue surrounding the ciliary body

Histology of ciliary process

Loose connective tissue, numerous penetrated capillaries and two layers of epithelium

Function of rods

Low light photoreceptor

How does water content and avascularity contribute to the enhancement of light transmission through the cornea?

Low water content due to water loss from both surfaces Avascularity and fine, well ordered collagen (type I) of stroma

Outer segments

Modified primary cilia and contain sacs of membranous saccules shaped as flattened disks

Choroidal Melanoma

Most primary ocular malignancy in Caucasians

What is the Conjunctiva

Mucous membrane which covers the exposed part of the eye

What is the only component of the Retina that is NOT a neuron?

Muller Cells

Sphincter pupillae muscle

Muscle bundles disposed in a circular array near the pupillary margin contained in the iris

What is more common open angle or closed angle glaucoma

Open angle glaucoma

This type of Glaucoma occurs when the trabecular meshwork drains the aqueous humor but the canal of Schlemm is obstructed Iridocorneal angle

Open-Angle Glaucoma

Obstruction of the Canal of Schlemm causes which type of Glaucoma?

Open-Angle Glaucome

Emrbyological origin of the Retina?

Optic Cup

Exit site for the Optic Nerve?

Optic Disk

What are the main three components of the eye that undergo development?

Optic stalk pigmented epithelium neural retna

Special regions of retinal layer

Ora Serrata optic disc fovea centralis macula lutea

Müeller cells

Organizing glial cells of the retina. Major supportive neuroglial cells of the retina which provide scaffolding for the neurons of the entire retina.

External stratified squamous epithelium

Outer covering of the cornea

What are the three tunics?

Outer fibrous middle vascular inner

Pigmented layer

Outer layer of the retina; epithelium resting on Bruch's membrane just inside the choroid. This pigmented cuboidal epithelium also lines the ciliary body and posterior iris, contributing to the double epithelium.

Scleral

Outer most layer of the eye

Suprachoroidal lamina

Outer part of the choroid bound to the sclera

Earlier implantation is better for children

P1 latency: time for sound at ear to reach cortex (measured by scalp electrodes), quickens as children age + pathways mature - deaf children given cochlear implants early can enter 1st grade w/ age-appropriate language skills. later, unable to achieve normal aud processing - decision cannot wait until child reaches age of consent

what makes up the membrane discs of photoreceptors

Primary acquired melanosis

Painless flat brown spot on eye

Spinchter muscle

Parasympathetically controlled

Ciliary body

Part of the more vascular middle layer

Iris

Part of the more vascular middle layer; gives the eye its color

What is found in the the corneal endothelium?

Permeable to air, Regulates Hydration of Stroma, Vital to transparency of Stroma; simple squamous or simple on cuboidal; cornea receives nutrients from aqueous humour through endocytosis

Rod cells

Pfft. Detects white and black, day and night. Extremely sensitive to light

Orbits

Protective areas of the skull where the eyes are located, which also contain cushions of adipose tissue.

Crystallins

Proteins that fill the cytoplasm of differentiating lens fiber cells

Dark hold in the middle of the iris

Pupil

Optic nerve

Photosensitive inner layer of the retina communicates with the cerebrum through this structure. On the eye's posterior side

What are the two layers of the ciliary processes

Pigmented Non-pigmented

What are the layers in the inner tunic?

Pigmented Epithelium, Neural Retina

What is the inner tunic composed of?

Pigmented epithelium Neural retina (light-sensitive)

Retina consists of?

Pigmented layer Neural layer

Eyelids

Pliable structures containing skin, muscle, and conjunctiva that protect the eyes

Adverse consequences of earliest form of cataract surgery.

Post-surgical astigmatism Increased incidence of retinal detachments Death of corneal endothelial cells in vitreous touch system Wearing heavy, uncomfortable coke bottle glasses Pain on bridge of nose from coke glasses sandbags on either side of head blood clots pulmonary infections falling at night

Choroid makes up what portion of the eye?

Posterior 2/3rd of the eye

Optic disk

Posterior area of the retina where the optic nerve leaves the retina is devoid of photoreceptors. Also known as blind spot.

Aging process of eye in which lens loses elasticity and can't get fatter.

Presbyopia

Horizontal cells and Amacrine cells

Processes that mainly spread horizontally in the plexiform layers and which integrate signals from photo receptors over a wide area of the retina.

Lacrimal glands

Produce fluid continuously for the tear film that moisturizes and lubricates the cornea and conjunctiva, and supplies O2 to the corneal epithelial cells.

Lacrimal glands

Produce fluid for the tear film Moisturizes and lubricates Supplies O2 to the corneal epithelial cells antibacterial

Which chamber is the Aqueous Humor produced?

Produced in the posterior chamber, then it travels into the Anterior Chamber. From anterior chamber, aqueous humor goes from Canal of Schlemm directly into the venous system Aqueous humor provides nutrients and oxygen for the lens and the cornea

Meibomian glands

Produces oils/sebum Forma a surface layer on tear film, slows evaporation, helps lubricate the ocular surface

Cause of secondary opacification.

Proliferation of remnant epithelial cells in sulcus at the equator which migrate over the posterior capsule. Corrected with laser.

Name the derivatives of the retina within the ciliary body and iris

Retina is made up of two layers: 1. the outer layer of the double epithelium is pigmented - this is the case for the entirety of the retina 2. the layer of photoreceptors - neural retina -retnal pigment epithelium (the entire retina) at the bottom, just above the choroid 3. the choroid: (part of uvia) nourishes the retina - bruch's membrane -choroidal stroma - chorocapillaris

List and describe the layes of the choroid

Retinal pigment epithelium, Bruch's membrane (collagen, elastic fibers), vascular choroid (incomplete fenestrations, supply outer few layers of retina), loose CT

What is the choroid made up of?

Rich in collagen, elastic fibers, fibroblasts, melanocytes, macrophages, lymphocytes, mast cells and plasma cells

Where does Lasik surgery cut?

Right under bowman's membrane

Pupil

Round hole in the middle of the iris

Inner Ear - pic

SC: semicircular canals U: utricle, S: saccule, V: vestibule, C: cochlea, B: bone.

what are the layers of the cornea from the outside in

SSNK Bowman's membrane Stroma Descemet's membrane Endothelium

Fibrous external layer of the eyeball Opaque white Posterior five-sixths Dense connective tissue containing Type I collagen bundles Fibroblasts Muscles insert into sclera

Sclera

Tough external layer of the eyes

Sclera

Outer layer of the globe

Sclera Limbus Cornea

The fibrous tunic consists of?

Sclera and Cornea

What does the Bruchs Membrane do?

Separates the choriocapillary layer from the retina Elastic fibers, collagen fibers Thickens with age

Fovea centralis

Shallow depression, having only cone cells at its center, with the bipolar and ganglion cells located only at the periphery. Increases visual acuity

7 morphological factors for lens transparency

Shape and arrangement of the lens fibers Regular intercellular interdigitations Small amounts of interstitial fluid Crystallin protein distribution within the lens fibers Absence of all organelles within mature lens fibers Smooth surface of the lens capsule Uniformity of the single layer of anterior epithelial cells

Myopic

Short sightedness

Cataract

Significant opacity of the lens which doesn't allow light to contract

Inner plexiform layer

Similar region of synapses between the bipolar and ganglion cells

Descemet's membrane found near the apical (air) surface or the basolateral surface?

Simple squamous epithelium, secretes Descemet's membrane.

What does the lens epithelium do?

Single layer of cuboidal cells Anterior surface of the lens At posterior edge of epithelium, cells divide to provide new cells that differentiate as lens fibers

Lens epithelium

Single layer of cuboidal epithelial cells. Present only on the anterior surface of the lens. The basal ends of the epithelial cells attach to the lens capsule, and their apical surfaces have interdigitations that bind the epithelium to the internal lens fibers.

Open angle glaucoma

Site of resistance to aqueous flow lie within drainage structures in the angle of the anterior chamber

Ciliary muscle

Small fascicles of muscle that insert on the sclera and are arranged in such a way that their contraction in response to parasympathetic nerves decreases the internal diameter of the ciliary body ring, reducing tension on the fibers that run from this body to the lens.

Albinism have .............. amount of pigment

Smallest

Oval Window of Vestibule

Space beneath E?

Tarsal glands (Meibomian glands)

Specialized sebaceous gland of the eyelid. Forms a surface layer on the tear film, reducing its rate of evaporation, and helps lubricate the ocular surface.

What is found in the corneal epithelium?

Squamous, stratified; Attached with hemidesmosomes; Innervated by unmyelinated axons

Name 2 major functions of this area.

Stem cell population Induction of root dentin

Five layers of the cornea

Stratified squamous nonkeratinized epithelium Bowman'ts layer (embryonic type I collagen) Stroma (Uniform type I collagen) Descement's layer (Type IV collagen) Endothelial cells with ATP pumps

Stroma

Substantia propria 90% of cornea's thickness About 60 layers of parallel collagen bundles (Type I) Avascular tissue Keratinocytes Receives nutrients from limbus and aqueous humor

Laser-assisted in situ keratomileusis (LASIK surgery)

Surgery that changes the shape or curvature of the cornea to improve certain visual abnormalities involving the ability to focus.

Macula lutea

Surrounds the fovea centralis. Here all layers of the retina are present, and the two plexiform layers are rich in various carotenoids, which give this are its yellowish color. Helps protect the cone cells of the fovea.

Pailloedema

Swollen optic nerve head secondary to raised intracranial pressure

ganglion cells

Synapse with bipolar and amacrine cells Axons from ganglion cells form the Optic nerve

Trabecular meshwork

System of irregular endothelium-lined channels that replace Descemet's membrane and its simple endothelium. Penetrate the stroma and allow slow, continuous drainage of aqueous humor from the anterior cavity.

Detached retina

That hurts. When the pigmented epithelium is separated from the photo receptor layer of the retina. In such regions, the photo receptor cells have no metabolic support from pigmented layer and choroid, and will eventually die.

What does the lens capsule do?

Thick, homogenous capsule Rich in proteoglycans and type IV collagen Protects underlying cells

What is the basolateral or basal domain?

The apical ends meet and the basal ends push away from each other (think of the double layer glove example that Dr. Sandig did in class - the glove would be epithelium with the outside being the basal layer)

Rod and cone cells

The cells responsible for detecting black/white and color. The outer layer of the neural retina

The ___________ is a highly vascular layer (arrowheads) of connective tissue containing melanocytes that prevent the reflection of incident light. Many of the nutrients for the retina come from _______ blood vessels.

The choroid is a highly vascular layer (arrowheads) of connective tissue containing melanocytes that prevent the reflection of incident light. Many of the nutrients for the retina come from choroid blood vessels.

What causes the pupils to have their black color?

The choroid which contains abundant melanocytes

Bleaching

The conformation changed induced by light in retinal which initiates the cascade of events producing neural activity. Also caused the chromophore to dissociate from the opsin

Cornea

The crowning tip of the eye

Describe what the dental lamina looks like. What are the swellings that appear along the lamina?? When do the swellings form?

The dental lamina looks like it will keep invading into the ectomesencyme, but the mitotic activity shows the ectomesenchyme is swelling above the dental lamina. The dental lamina will be pushed deeper into the jaw.

Explain the BELL STAGE

The enamel organ will resemble a bell and the crown assumes its final shape (morphodifferentiation). • Histodifferentiation pertains to differences in cell shapes or organelles. The enamel organ will resemble a bell and the crown assumes its final shape (morphodifferentiation). • Histodifferentiation pertains to differences in cell shapes or organelles. Note how the inner dental epithelium has taller, columnar cells than the cuboidal cells of the outer dental epithelium. New layer forms stratum intermedium! • Important later for mineralization/formation of enamel. • Ameloblasts are derived from the inner enamel/dental epithelium. Stellate reticulum cells are held together by desmosomes while secreting GAGs which push them apart (making them into stars) • Stratum intermedium cells will sit right on top of the inner enamel epithelium. Note how the inner dental epithelium has taller, columnar cells than the cuboidal cells of the outer dental epithelium. New layer forms stratum intermedium! • Important later for mineralization/formation of enamel. • Ameloblasts are derived from the inner enamel/dental epithelium. Stellate reticulum cells are held together by desmosomes while secreting GAGs which push them apart (making them into stars) • Stratum intermedium cells will sit right on top of the inner enamel epithelium.

Sclera

The first concentric tunic; a tough external layer that also consists of the cornea.

The________ regulates the amount of light that enters the eye.

The iris regulates the amount of light that enters the eye.

• What induces cells of the dental papilla to differentiate into odontoblasts?

The pre-ameloblasts forming from the IDE

• What induces the ameloblasts to start producing enamel?

The production of dentin from odontoblasts

What Determines Eye Color?

The stroma and the melanocytes give the eye its color.

The primary epithelial band will branch into two invaginations.

The tooth germ (dental lamina) and Vestibule of the mouth (vestibular lamina) - the space between the lips/cheek and the teeth!

Uvea

The vascular middle layer of the eye. Consists of the choroid, the ciliary body, and the iris

What is found in the Decemet's Membrane?

Thick basement membrane, Type IV collagen

what does transducin do

blocks Na channels to decrease NT release

What is the first visible sign (with a microscope...) of tooth initiation? When does it form? How is it created?

Thickening in the mandibular process. This is called the Primary epithelial band (also discussed in cranial neural crest)

Ciliary body

Thickening of the middle layer. In close apposition to the vitreous body on its posterior side

Bruch's membrane

Thin amorphous hyaline sheet that separates the choriocapillary layer from the retina. Extends from the ora serrata back to the optic nerve

Conjunctiva

Thin, transparent mucosa that covers the exposed, anterior portion of the sclara and continues as the lining on the internal surface of the eyelidseyelids

Draw a diagram of a tooth germ at bud stage.

Things that should be labeled: dental lamina, tooth bud, ectomesenchyme condensation and oral epithelium. The position of the basement membrane should be highlighted.

Lens is made up of what three components??

Three components: lens capsule, lens epithelium, lens fibers

What is the second cause of world blindness?

Trachoma - infection causes eye lashes to turn in. With every blink, there is abrasion of the cornea stroma. This causes the keratocytes to switch from synthesizing type 1 collagen to type III collagen fibers which are randomly arranged and scatter light. Results in corneal opacification.

Opsin

Transmembrane protein with a bound chromophore that is found in each visual pigment

Cornea

Transparency: transporting Na+ to apical surface -maintained by Corneal epithelium/endothelium -dehydrated stroma

Cornea Transparency

Transparency: transporting Na+ to apical surface -maintained by Corneal epithelium/endothelium -dehydrated stroma

Histology of vitreous

Transparent gel Collagen filaments

Vitreous body

Transparent, gelatinous mass of connective tissue in the vitreous chamber

Steps in penetrating keratoplasty

Trephination Healon injection Sutures (running versus interrupted) Non introduction of post-surgical astigmatism

What is found in the bowman's capsule?

Type I collagen; Barrier to trauma and bacterial invasion

The lens capsule is composed of

Type IV collagen

What type of collagen is descemet's membrane composed of?

Type IV collagen

Chromophore

Uhhh... Ha. Ha. Ha. It's a molecule that is light-sensitive

Myoepithelial cells

Underlying epithelial layer of the iris is composed of these types of cells, which are at least partially pigmented

Ways to test intraocular pressure

Use two fingers Tonopen (puff of air) Schiotz tonometry (plunger on cornea at slit lamp)

Rhodopsin (visual purple)

Visual pigment which is bleached by light and initiates the visual stimulus

Idiopsin

Visual pigment with maximal sensitivities in the red, blue, or green regions of the visual spectrum, which enables these cells to detect those colors in reflected light.

Which vitamin is important for vision?

Vitamin A (Retinal)

Chambers of the eye

Vitreous Anterior Posterior

Transparent, gelatinous mass of connective tissue Lies behind the lens

Vitreous body in vitreous chamber

What is the aqueous humor made of?

Water, amino acids, glucose

What is the function of cone cells?

Wavelength discrimination and visual acuity

- tight junctions at apical border (forms blood retina barrier) - basal infoldings - contains melanin granules - esterifies vitamin A - phagocytoses shed tips of rod outer segments - cuboidal---> columnar cells - attached to Brunch's membrane

What are the characteristics of the pigmented epithelium in the retina?

Ciliary muscle

What part is this pointing to?

Cataract

When the lens becomes opaque or cloudy and vision is impaired. Usually caused by the denaturation of crystallins.

tertiary bronchus

Where is this slide from?

Drusen - Causes which disease?

Yellow deposits in Macula (Macular Degeneration). Form between Choroid and Bruch's Membrane. Push up the retinal pigements layer.

what is cataracts specifically?

a condition by which the crystalline within lens fibers gets cross-linked in an inappropriate manner, so light can't get through, and lens becomes opaque

what is the canal of schlemm

a small vessel which encircles the eye near the s/c junction (used to drain aqueous humor from the eye

what is the hyaloid canal?

a vestige of the canal that contains hyaloid artery, which passes to the lens during embryonic development contains a clear fluid in adult life

What is the function of the zonular fibers?

a-cellular fibers that extend from the basement membrane of the ciliary processes, and attach to and suspend the lens

describe the structure and function of the optic disc or papilla

a. entrance of retinal blood vessels b. exit of ganglion cell axons (optic nerve = no photoreceptors = blind spot) c. layers: neural retina, RPE, choroid

What is the function of the aqueous veins?

about 20-30 of these veins drain aqueous humor from canal of schlemm and empty it into the venous system

crystallins

abundant cytoplasmic proteins produced during elongation of cells in lens development

zonular fibers that attach to the ciliary body function to ___

accommodate the lens

what does the crystalline protein do?

allows light to pass through these fibers in an un-impeded manner

Ciliary is the ............... portion of the choroid

the ____ chamber is between the cornea and the iris

What are the three chambers of the eye?

anterior posterior vitreous

Space between cornea and iris

anterior chamber

Where are lens fiber cells derived from?

anterior lens epithelium

Iris

anterior of the vascular layer (urea) surrounds and helps control the diameter of the pupil pupil is iris central opening

Iris

anterior of the vascular layer (urea) surrounds and helps control the diameter of the pupil pupil is iris central opening -covers lens -pupil -anterior surface -posterior surface -spinchter muscle

Ciliary Body

anterior, thickened extension of choroid layer concentric ring of smooth muscle around the opening in which the lens is suspended main part of ciliary body is continuous with the *choroid* includes ciliary muscle/body ciliary processes zonular fibers

Glands of Moll

apocrine glands w/eyelashes modified sweat glands that empty into the eyelash follicles

Explain the Late bell stage

appositional stage The beginning of dentin & enamel formation. It starts at the tips of the future cusps. • IDE form into pre-ameloblasts triggers • Adjacent papilla cells to become odontoblasts • Odontoblasts secrete dentin which triggers • Ameloblasts to secrete enamel. Dentin is always formed before enamel. The enamel will ODE will become the reduced enamel epithelium. o The dental papilla will also secrete their own GAGs which swell the papilla with water (just like the stellate reticulum) This allows for equal pressure on both sides of the epithelial wall. When the first calcified matrix appears (of dentin & enamel), the dental papilla is called the TOOTH PULP. o Later on, the lamina fragments from the tooth (both general & lateral) which leave it separated & isolated in the oral epithelium. If it doesn't degenerate, you'll have epithelial pearls (cysts)

What fluid does the cornea contain?

aqueous humor

What kind of fluid do both the anterior and posterior chambers contain?

aqueous humor

what are the anterior and posterior chambers filled with

aqueous humor

what does the outer epi of the ciliary processes produce

aqueous humor

Trabecular meshwork

aqueous humor exit point

macula lutea

area around fovea centralis plexiform layers have a high concentration of carotenoids

what is the fovea?

area of greatest visual acuity; overlying layers diverge; mainly cones

What does transparency of the stroma depend on?

arrangement and affinitiy to water

Describe the vessel layer of the choroid

arteries, veins pigmented cells choriocapillaris capillaries

Secretory cells

becomes the pigmented cells of the iris

What are the posterior and anterior limits of the ciliary body?

begins at the ora cerrata (irregular ring where nervous retina ends) extends forward as far as the root of the iris

what are the limits of pupil intraocular pressure?

between 10 and 20 mmHg

vitreous body

between retina and lens

Anterior Chamber

between the iris and cornea's innermost surface

the axons of the photoreceptor cells synapse with dendrites of the ____

bipolar cells

What Connect rod and cone cells of the intermediate layer?

bipolar neurons

the inner nuclear layer contains the nuclei of what cells

bipolar, muller, horizontal, and amacrine cells

what does the optic disc cause

blind spot

function of pigmented layers of iris

block light

melanocytes

block light abundant in choroid

lymphatic nodules

both are...

nucleus

bottom lines pointing / dark stained structures

name the structures which surround the anterior chamber

bounded by cornea, iris and lens

name the structures which surround the posterior chamber

bounded by lens, iris, ciliary processes, zonule

describe the layer of the photoreceptors of the retina

broken into two groups: 1. neural retina 2. retinal pigment epithelium (the entire retina) at the bottom just above the choroid

how is aqueous humor produced?

by ciliary processes through diffusion from capillaries and secretion from ciliary epithelium

Contiunous

capillaries in the Iris

Describe the vascular layer of the ciliary body and state which layer of the choroid it corresponds to

capillaries, arteries and veins corresponds to the vessel layer of the choroid

differences in eye color

caused by -variable arrangement of connective tissue network -differing concentrations of melanin in melanocytes

Vitreous Chamber

cavity posterior to the lens containing gelatinous vitreous body 99% water +*hyaluronate* surrounded by membrane of type 4 collagen hyalocytes near membrane produce hyaluronate and collagen

What does the vestibular lamina become? Describe the process.

cells proliferate, enlarge then degenerate/undergo apoptosis. The (programmed cell death) of cells in the vestibular lamina form a cleft, which is the VESTIBULE.

Where are cone cells concentrated?

center of the eyes; more active in greater light

Zonules

change shape of lens

what is accomadation

changing the shape of the lens with sm. m. contraction of the ciliar body

the part of the choroid that contains blood vessels is called:

choriocapillaris

what is the iris continuous with

choroid

which tunic is vascular

choroid

the uvea is composed of:

choroid, ciliary body, and iris

the sclera is connected to the ___ which is vascularized, by a loose connective tissue known as ___

choroid, suprachoroid lamina

the part of the choroid that doesn't contain blood vessels:

choroidal stroma

what produces aqueous humor

ciliary processes

what is the pathway of aqueous humor

cilliary processes posterior chamber anterior chamber

What is bowman's layer made up of?

collagen (type I) corneal epithelial cells

Bowman's Membrane

collagen fibrils

Bowman's Membrane

collagen fibrils -basement membrane for outer epithelium -acellular, doesnt regenerate

How is the stroma attached?

collagen lamellae at an angle to one another

what does modulating mean

combining impulses from several rod or cone cells

Lens capsule

composed of type 4 collagen and proteoglycans surrounds lens

Limbus (details)

concentration of stem cells for re-epithelializing injured corneal epithelium endothelial lined channels merge to form *Canal of Schlemm*

describe the general stroma of the iris

connective tissue, highly vascular pigmented cells DOES NOT CORRESPOND TO A CHOROID LAYER

anterior layer of iris

consists of fibroblasts and melanocytes

posterior layer of iris

consists of heavily pigmented epithelial cells and lightly pigmented myoepithelial cells

what muscles control the iris dilation

constrictor and dilator pupillae (sm.m.)

synaptic terminal(rods and cones)

contact with bipolar neurons

inner (front) segment (rods and cones)

contain the metabolic machinery for the cell

conjunctiva

contains goblet cells that can secrete tears

Macula lutea

contains whole foveal area - retinal region about 3mm in diameter that contains yellow pigments (*xanthophyll carotenoids*); these pigments filter out high-energy (lowwavelength) blue light, including some near-UV radiation, which can cause retinal damage

iris

continuous with choroid central hole, the pupil, allows passage of light

Describe the epithelium of the iris

continuous with the corneal endothelium composed of simple squamous/cuboidal cells DOES NOT CORRESPOND TO A LAYER OF THE CHOROID

what is the choroid continuous with

continusous with uveal tract

What is the function of the ciliary muscle?

contraction facilities accommodation of the lens attached to ciliary body

What is the function of the dilator Pupillae?

contraction of the pupil, which increases the diameter/ dilates the pupil

Ciliary Muscle

contracts to change shape of lens

Ciliary muscle

contracts to focus image on photosynthesize cells

overlying ectoderm forms

cornea

the ___ is transparent

cornea

the sclera is continuous with what

cornea

what tissue is one of the few that can be transplanted without immunorejection

cornea

Supporting Layer

cornea and sclera

the limbus is also the place where there is a transition between the ___ and the ___

cornea and the epithelium of the conjunctiva

layers of cornea:

corneal epithelium, Bowman's membrane, stroma, Descemet's membrane, endothelium

cochlea

cross section - whole thing

what does subcapsular epithelium produce

crystallin

Visual processing of Light (beginning)

dark photoreceptor cells are depolarized Na+ channels open continuous release of neurotransmitter to *bipolar* neurons

Ora serrate

demarcation for anterior/posterior portion of retina

what kind of CT will you find in the sclera

dense fibrous CT

corneal stroma (substantia propria)

dense irregular fibroblast cells-keratocytes secrete ground substance and perpendicular type 1 collagen fibers doesnt regenerate

The Primary epithelial band is in the position of the future ___.

dental arches

Drusen

deposits of amyloid material that break the membrane of retinoic pigmented epithelium and induces photoreceptor degeneration

Lens embryologic development

develops from surface ectoderm (not neurectoderm) invagination (turning inside out) of ectoderm forms lens vesicle lens vesicle separates from overlying ectoderm cells lining posterior surface of the vesicle elongate anteriorly the cells lining the anterior vesicle persist

Ciliary muscle (3 groups)

differ in fiber direction and insertion site Longitudinal portion inserts in choroid stroma radial portion radiates outward and inserts in fibrous part of ciliary body circular portion is oriented concentrically (having common center like circles)

Posterior surface

do not cubodial cells

how often do the external cell layer turn over

every 7 days

what layers are for lateral integration

external and internal plexiform layer

ELL

external limiting layer apical boundary of Muellers cells

Sclera

external white part of eye composed of *dense connective tissue* 0.5 mm thick continuous with cornea (anteriorly) continuous with epineurium of optic nerve (posteriorly) exposed surface (anterior and including cornea) covered by a thin *non keratinizing squamous epithelium* made of type 1 collagen and elastin -maintain size and shape of eye -nonvascular -anteriorly covered by Bulbar Conjunctiva -Posteriorly covered by bulbar sheath

What does bowman's layer contain?

extracellular matrix

what does the canal of schlemm drain into

extraocular vv.

Which protein protects the eye from UV radiation?

ferritin protects from UV, not melanin

What is the stroma made up of?

fibroblasts

What type of tissue is the elastic plate made out of?

fibroelastic

What do lens fiber cells produce?

filensins and crystallins

What is the location and function of the vitreous body?

fills the space posterior to lens, supports the retina attached at the ora serrata and optic disc, loosely attached to inner limiting membrane

What is the vitreous chamber composed of?

fluid (more than 90% is H20) but many proteins give it a gel like texture

Cuboidal epithelium

give rise to lens fibers

What happens if intraocular pressure increases?

glaucoma results because when intraocular pressure exceeds vessel pressure, blood flow to the retina is reduced

What is the main metabolite of a cataract?

glucose

What are the 3 contents of the aqueous humor?

glucose, H2O, amino acids

Cornea

has no blood vessels

What causes glaucoma?

if intraocular pressure exceeds vessel pressure then blood flow to retina is reduced

tapetum lucidum

in nocturnal animals, bounces light back to photoreceptors

Sphincter pupillae muscle

in stroma of iris - smooth muscle - by shortening (parasymp), reduce pupil diameter

where is the Choriocapillaris found?

in the choroid, underneath the retinal pigment epithelium

where is aqueous humor found?

in the posterior and anterior chambers - it is constantly produced and drained

glaucoma

increase pressure in the anterior and posterior chambers resulting from blockage of the circulation of aqueous humor in the channels of the Limbus

the ___ tunic is composed of the retina

inner

ILL

inner limiting layer basal layer of Muellers cells

INL

inner nuclear layer cell bodies of Muellers cells and bipolar and association neurons

IPL

inner plexiform layer processes of association neurons, bipolar neurons, and ganglion cells that connect to each other

Pigmented epithelium

inside

Limbus

interface between sclera and cornea

Describe bruch's membrane of the ciliary body and state which layer of the choroid it corresponds to

it continues as two layers corresponds to Bruch's membrane of the choroid

what is characteristic of the choroid

it is heavily pigmented

what is the function of the extracellular matrix of Bowman's layer?

it is made up of coreneal epithelial cells which act as a sieve ON WISCONSIN! :)

what is in the internal plexiform layer

it is the region of synapse between bipolar and ganglion cells

How does the lens of the cornea enhance light transmission?

it reflects light ***

what happens in the external limiting membrane

junction of photoreceptors and muller cells not a synapse

Outer limitimg membrane

junctional complex between muller cell and receptor cell

Melanocytes

keep stray light from interfering with image formation

Melanocytes

keep stray light from interfering with image formation block light abundant in choroid

ciliary epithelium

label 2

Cones

less sensitive to low light iodopsin 3 forms of cones each sensitive to a different wavelength (R, B, or G) each cone cell contains *one* form of iodopsin 7 million cone cell in human retina

Cones

less sensitive to low light iodopsin 3 forms of cones each sensitive to a different wavelength (R, B, or G) each cone cell contains *one* form of iodopsin 7 million cone cell in human retina - packed at high densities within retina - provide high resolution, fine-grained image - daylight! - more in central retina (fovea) - rods absent from foveal pit

Rods and cones

light reaching these cells must first pass through all layers of neural retina

decements membrane

like a thick basal lamina that regenerates- lays down corneal endothelium

what is the area between sclera and cornea called

limbus

the junction between the sclera and cornea is the ___ and is known to ___

limbus, harbor stem cells

Lacrimal glands

located above and slightly lateral to orbits tubuloacinar glands

Lacrimal glands

located above and slightly lateral to orbits tubuloacinar glands 分泌淚液

describe the epichoroid layer of the choroid

looes layer elastic fibers pigmented cells

which is more relaxing? looking into the distance or reading a book? Why?

looking into a distance is more relaxing because the ciliary muscle relaxes

the ___ tunic is composed of the uvea: choroid, ciliary body and iris

middle

Vascular Tunic (CIC)

middle layer -Iris -Ciliary Body -choroid

what does the ganglion cell layer do to the signal

modulates the impulses going to optic nerve

what does the inner nuclear layer do to the signal

modulates the signal

tears

moisturize, lubricate supply oxygen to corneal epithelial cells lysozyme (antibacterial)

choriocapillary lamina

more vascular layer of Choroid bound to underlying Bruch's membrane

route of aqueous humor

moves from posterior to anterior chamber, then through the Canal of Schlemm

Inner Ear

name this region?

Middle Ear

name this region?

Pupil

name this space

where do lens fiber cells divide and elongate?

near the equatorial region

what are the layers of the optic disc or papilla?

neural retina RPE choroid

• What is the cervical loop?

o Cervical Loop Where the internal & external dental epithelia meet at the rim of the enamel organ. Site of high mitotic activity (maybe they're stem cells for IDE) to make the crown bigger After crown formation is complete, epithelial component of root formation starts. • Root formation happens AFTER crown formation is complete. • Hertwigs Epithelial Root Sheath (HERS) forms which induces root dentin formation.

• At cap stage, which is the instructive tissue: epithelium or ectomesenchyme?

o During cap stage, ectomesenchyme tells the epithelium to make the crown.

• How is tooth number established? Describe a syndrome that may be caused by lack of Eda.

o Each kind of tooth has a specific number in its tooth field (i.e. 2 incisors, 3 molars) Epithelium secrets Eda which controls the size of the tooth field. Lack of Eda causes less teeth • Can be from hypohidrotic ectodermal dysplasia (HED) which also effects hair, sweat glands, nails and salivary glands. Extra Eda makes more teeth.

• What is the role of the enamel knot? At which stage is it active? How does it affect cells of the IDE?

o Enamel Knot --> Secretes signaling cells that organize the shape of the cusp. Everywhere you have an enamel knot, you are going to have a cusp. Seen at cap stage as a cluster of cells at the center of the enamel organ. Formation of enamel knot is managed by underlying mesenchyme. • The enamel knot becomes an enamel cord, lying between the inner & outer dental epithelia. o Both tell the cusp where to form (maybe due to stopping mitosis and start differentiation) o One knot per cusp.

• What is the role of the enamel knot?

o Enamel Knot Secretes signaling cells that organize the shape of the cusp.

• What increases the volume of the stellate reticulum? What keeps the cells attached to each other?

o Glycosaminoglycans (GAGs) are secreted by stellate cells which pull water into the enamel organ. Negative charges are what attract water and make the reticulum loose. o Volume increases and cells are forced apart, but are still connected by desmosomes (-->star shape) The increase of volume allows room for crown formation.

• How are the cells of the IDE nourished? Where are the blood vessels?

o Nourishment of enamel organ & IDE Capillaries sit close to the outside of the outer enamel epithelium, so wastes & nutrients can move through the stellate reticulum and nourish the enamel organ. o Columnar cells in the IDE are rich in RNA & glycogen. Note - "cell free zone" between IDE and papilla. IDE will differentiate into pre-ameloblasts (which will become ameloblasts to form enamel) o The stratum intermedium has 2-3 layer thickness over the IDE. They will be the transporters to and away from the ameloblasts. Rich in alkaline phosphatase to help ameloblasts form enamel.

• Explain the concept of the "odontogenic homeobox code". Which tissue creates the axes? How?

o Odontogenic homeobox code The shape of the tooth that will be formed according to the combination of homeobox genes that have been induced in the ectomesenchyme into which the tooth bud invaginates. o The axes are made by the epithelium. Proximal jaw epithelium secretes FGF8 signaling molecule which sets up the molar field. Distal jaw secretes BMP4 which sets up the incisor field.

• Describe the position of the permanent tooth bud on the dental lamina, and its relation to the primary tooth.

o Primary teeth will develop from the buds first and then the edge of the dental lamina will continue deeper into the jaw to make the successional lamina which will form the permanent teeth. The main ridge is the general lamina The cross ridge that connects with the primary tooth is the lateral lamina The successional lamina will give the tooth germ for permanent teeth. o The permanent tooth bud always develops on the lingual side of the primary tooth!

o _______________ gives the area for dentin to ____ (less collagen fibrils)

o The Cell-free zone, form

• In the initial stages of tooth induction, which is the instructive tissue: epithelium or ectomesenchyme?

o The epithelium instructs the ectomesenchyme.

• What occurs if the general lamina does not fully degenerate?

o The general lamina generate the permanent molars because there is no deciduous teeth (non-succedaneous) o If it doesn't fully degenerate, you'll get an extra tooth/teeth. Note successional lamina is more toward lingual side. o Also, if they don't degenerate, they can form epithelial pearls (cysts) Cysts will form over the developing tooth and delay eruption. Can also lead to formation of supernumerary teeth (extra teeth) • Similar to what occurs in the palate (epithelial cysts in seams)

o The permanent tooth _____ always develops on the ______________ side of the primary tooth!

o The permanent tooth bud always develops on the lingual side of the primary tooth!

glaucoma

ocular disorders resulting in optic nerve damage, often associated with increased fluid pressure in the eye, can lead to blindness

what is the optic papilla

optic disc

Pigmented cells

of the cilliary processors become the dilator muscle of the iris

what are the molecules of the pigment protein complex

opsin retinal transducin

stroma

orthogonally (right angles) arranged collagen bundles collagen types 1 and 5 precise spacing between bundles maintained by *keratocytes*

the ___ tunic is composed of the sclera and cornea

outer

Corneal transparency contributing factors

outer and inner surfaces of epithelial layers are smooth arrangement of stroma collagen bundles tightly regulated hydration of storm maintains spacing of collagen bundles

suprachoroidal lamina

outer choroid layer bound to sclera

Cornea (5 layers)

outer layer Bowman's membrane stroma (substantia propria) Descemet's membrane inner layer 2 cell layers, 2 basement membranes, 1 intervening storm

what type of cells are in the internal limiting membrane

outer layer of the muller cells

ONL

outer nuclear layer cell bodies of rods and cones

OPL

outer plexiform layer processes of rods and cones and of bipolar and association neurons

Rods and cones cell regions (4)

outer segment connecting stalk inner segment synaptic terminal

Secertorial Epithelium

outside

the constrictor muscle of the iris is innervated by ___ fibers

parasympathetic

what is the sphincter pupillae innervated by?

parasympathetic nervous system

after production, where and how does aqueous humor travel?

passes from posterior chamber to anterior chamber via pupil intraocular pressure that needs to be maintained

rod photoreceptors are responsible for:

peripheral vision

Limbus channels

permit circulation of aqueous humor from the chambers existing between cornea and lens (anterior, posterior chambers)

what is accomodation?

permits the focusing on near and far objects by changing the curvature of the lens Ciliary muscles

neural retina

photoreceptive layer of retina

the horizontal cells can synapse with the axons of the ___ cells

photoreceptor

Neural retina cells

photoreceptor cells: rods and cones conducting neurons: bipolar neurons and ganglion cells association neurons: horizontal, centrifugal, interplexiform, amacrine neurons supporting cells: Muellers cells, micro glia, astrocytes

what happens in the external plexiform layer (reason for lateral integration)

photoreceptors synapse with bipolar cells

The rods and cones are the outer layer of?

photosensitive cells

what are the layers of the retina

pigment epithelium rods and cones external limiting membrane external nuclear layer external plexiform layer inner nuclear layer internal plexiform layer ganglion cell layer nerve fiber layer internal limiting membrane

the ____ chamber is between the iris and the lens

posterior

What is the two-layered epithelium with melanin granules and Pigmentation of the iris prevents light from entering the interior of the eye, except through the pupil

posterior chamber

space between iris, ciliary processes, zonular attachments and lens

posterior chamber

what is the function of hyalocytes (which are found in the vitreous body)

produce some collagen and hyaluronic acid

Ciliary Process

produces aqueous humor

Ciliary Process

produces aqueous humor projections of ciliary body surface into *posterior* chamber covered with 2 layers of *low columnar epithelium* outer layer inner layer

ciliary processes

projections of ciliary body surface into *posterior* chamber covered with 2 layers of *low columnar epithelium* outer layer inner layer

What is the function of the outer fibrous tunic?

protection

what are crystallins?

proteins that fill the cells of the lens substance after those cells become devoid of a nucleus and other organelles

How does the curvature of the cornea enhance light transmission?

refracts the light onto the retina ***

Iris

regulates light

Optic Nerve

regulates light

is the sclera avascular or vascular?

relatively avascular

The inner sensory layer that is made up of neurons

retina

pigmented layer (outer layer)

retina later adjacent to Bruch's membrane

retinal layer

retina proper and non-nervous anterior portion

What can floaters indicate

retinal detachment

Rods

sensitive to low light rhodospin 120 million rod cells in human retina

Bruch's membrane

separates choriocapillary layer from retina

Bruch's membrane

separates the choroid from retinal layer

cones are responsible for:

sharp vision, specific color vision

describe bruch's membrane of the choroid

shiny, homogenous basement membrane and elastic fibers

What does the vitreous chamber act as?

shock absorber

connecting stalk (rods and cones)

short constricted segment between cell segments modified cilium (basal body and microtubules)

describe the posterior pigmented epithelium of the iris and state which layer of the choroid it corresponds to

simple cuboidal heavily pigmented corresponds to the nervous retina layer of the choroid

describe the pigment epithelium of the ciliary body and state which layer of the choroid it corresponds to

simple cuboidal heavily pigmented corresponds to the pigment epithelium of retina layer of the choriod

describe the ciliary epithelium of the ciliary body and state which layer of the choroid it corresponds to

simple cuboidal non-pigmented corresponds to the nervous retina layer of the choroid

What type of cells make up the corneal endothelium?

simple low cuboidal epithelium

Corneal Endothelial

simple squamous epithelial -next to decemet's membrane

inner layer

simple squamous epithelium maintains hydration of stroma also called endothelium

outer (back) segment (rods and cones)

site of photoreceptor cells membrane discs increase surface area photosensitive molecules located in membrane discs

optic disc

site on posterior retina where axons converge and exit eye as optic nerve

fovea centralis

site on posterior retina with high concentration of cones no rods

Eyelid

skin on the outside, conjunctiva on inner surface large hair follicles at interface of epithelia form eyelashes area of fibroelastic tissue (tarsus) provides physical support

anterior chamber

space between iris and cornea both chambers filled with aqueous humor and are interconnected through the pupil

Posterior chamber

space between iris and lens both chambers filled with aqueous humor and are interconnected through the pupil

posterior chamber

space between iris and lens both chambers filled with aqueous humor and are interconnected through the pupil - formed by iris (anterior) - lens and zonule (posteriorly) - and ciliary process (peripherally)

ciliary body

specialized extension of the choroid helps control the shape of the lens

Anterior surface of Iris

spongy stroma -Fibroblast, collagen, melanocytes

Conjuctiva

stratified low columnar epithelium covers anterior sclera and inner surface of the eyelid contains small number of mucous secreting cells Limbus = white bulbar - white with red blood vessels forineal- pinkish hue over white tarsal- red backside of eyelid

What type of cells make up the corneal epithelium?

stratified squamous

anterior corneal epithelium

stratified squamous non keratinized. renewed once a week. free nerve endings (occulomotor...)

Muller cells

structural support

spleen

structure?

what cells produce lens fibers

subcapsular epithelium

what is the function of the hyaloid membrane?

surface condensation of collagen fibrils

ciliary zonule

suspensory ligament of lens

what are zonula fibers also called?

suspensory ligaments

the dilator muscle of the iris is innervated by ___ fibers

sympathetic

what is the dilator pupillae innervated by?

sympathetic nervous syste

Outer plexiform layer

synapse between photoreceptor and bipolar cell

plexiform layers contain ___

synapses between cells

Ganglion cell layer

talk to brain

When does vestibular lamina form?

the 7th week

• Draw a diagram of a tooth germ at cap stage.

the enamel organ, the dental papilla, the dental follicle (sac) should be labeled. Highlight the position of the basement membrane.

where is the retinal pigment epithelium located?

the entire retina, at the bottom, just above the choroid

where are the lens fiber cells moving toward?

the lens nucleus

What layer of the choroid do the ciliary epithelium of the ciliary body and the posterior pigmented epithelium of the iris correspond to?

the nervous retina

the processes of the ganglion cells form ___

the optic nerve

what are the two layers of the retina?

the outer layer and the layer of the photoreceptors

What si the neural retina?

the photosensitive part of retina

What layer of the choroid corresponds to the pigment epithelium of teh ciliary body and the dialator muscle of the iris?

the pigment epithelium of retna

at the ora serrata, the retina ends. its pigmented layer becomes what

the pigmented layer of the ciliary epithelium

What is the optic disc?

the raised disk on the retina lacking visual receptors and so creating a blind spot. - entrance of retina blood vessels - exit of ganglion cell axons (optic nerve)

corneo-scleral coat, uvea, retina

the three layers of the eye

what is the sclera and where is it found?

the white of the eye • found underneath the choroid

what do the lens fiber cells get rid of as they move inward?

their nucleus

what is special about iodopsin

there are 3 variations for different wavelengths

importance of retinoic pigmented epithelium

they are in close contact with the outer segments of the photoreceptors- serves as a blood barrier, also serves as nutrient support, phagocytosis for the outer segment of the photoreceptors, contains rodoxin

zonular fibers

thin collagen fibers + elastin/fibrillin suspend lens from ciliary body under tension when ciliary muscle is relaxed -tension flattens lens (far vision) fiber relax when ciliary muscle contacts -lens becomes thicker for near vision

What is aqueous humor?

thin watery fluid composed of water, protein and glucose

relaxed ciliary muscle

tight zonular fibers thin lens far vision

vein

top line - whole structure

intercalated discs

top lines pointing

ciliary processes outer layer

toward surface of eye heavily pigmented continuous with pigmented epithelium (outermost layer of retina)

Where do lens fibers move?

towards the lens nucleus

What drains the aqueous humor?

trabecular meshwork canal of Schlemm aqueous veins - drains from the canal of schlemm into a venous system

how is aqueous humor drained

trabecular meshwork mass of sponge-like tissue at the sclero-corneal junction CANAL OF SCHLEMM aqueous veins

Lens

transparent structure behind iris embryologic development key to understanding lens structure beaded filaments within the lens composed of intermediate filaments, *phakinin* and *filensin* are thought to contribute to lens transparency lens capsule surrounds the lens

Retinal detachment

trauma and physical shock can cause separation of 2 layers of retina pigmented epithelium and neural retina

How many layers is the retina made up of?

two

What type of collagen is Bowman's layer made up of?

type one

What is the corneal epithelium innervated by?

unmyelinated axons

Why does it hurt when something is stuck in your eye?

unmyelinated nerve fibers travel through the stroma and infiltrate the cornea

the more vascular middle layer of the eyes, consisting of choriod, ciliary body and iris

uvea

what is the choroid a part of?

uvia

Uvea

vascular later consisting of -iris -choroid -ciliary body

what maintains the transparency of the cornea

very regular arrangement of collagen layers

iodopsin

visual pigment of cones

rhodopsin

visual pigment of rods

What is Rhodopsin?

visual pigment, bleached by light and initiates the visual stimulus

the ____ cavity is behind the lens

vitreous

What are the 3 contents of the aqueous humor?

water, amino acids, glucose (WAG)

venules

what will arterioles ALWAYS be paired with?

What is the role of the ciliary muscle in the focusion of the lens (accommodation)?

when the ciliary muscle is relaxed the lens is flattened by tension of the zonule when the ciliary muscle contracts, tension in the zonule decreases and the lens thickens

optic papilla

where axons converge to form the optic nerve

lung

where is this slide from?

tertiary bronchus

where is this slide from?

Lamina Cribrosa

where optic nerve pierces the sclera

Corneo Iridial angle

white V shape next to the trabecular meshwork

lymph node

whole structure

muscular artery

whole structure

trachea

whole thing

what is the structure and function of the macula lutea?

yellow, pigmented area surrounding the fovea (absorbs excess blue and UV light)

carotenoids

yellow-orange pigment

what do the ciliary processes anchor

zonule fibers

what suspends the lens to ciliary body

zonule fibers

Characteristics of Stroma?

• Collagen lamellae at angle to one another • Transparency depends on arrangement and affinity to water

Characteristics of corneal endothelium?

• Permeable to air • Regulates Hydration of Stroma • Vital to transparency of Stroma • simple squamous or simple on cuboidal; cornea receives nutrients from aqueous humour through endocytosis

Characteristics of corneal epithelium?

• Squamous, stratified epithelium • Attached with hemidesmosomes • Innervated by unmyelinated axons • not epidermis *

Characteristics of Decemet's Membrane?

• Thick basement membrane • has Type IV collagen

Characteristics of Bowman's capsule?

• Type I collagen (orthogonally arranged) • Barrier to trauma and bacterial invasion

Histology Eye

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