Microanaotomy of Eye Flashcards
Function of eye
Photosensitive organ allowing analysis of shapes , colours and light intensity of objects.
Describe the location of the eyeball
In orbits of the skulls , cushioned by adipose tissue , protected anteriorly by eyelids. and eyelashes and continuously bather in fluid fro the lacrimal gland
What gland causes Tears
Lacrimal gland
Clinical name of eyelid and what is it made of
Palpebral
composed of skin and muscle
What is the white part around the iris of the eye called
Sclera
What is the conjuctiva
Lines the inner parts of eyelids and extends over onto the sclera of eye
When eyelids move over the sclera what are they doing
Helping to distribute Tear film made of aqueous solutions and oily secretion
What is the palpebral fissure
Corner of eye , opening between upper and lower eyelids
What are the names of the angles of the palpebral fissures
Medial commisura and lateral commissure
What is the lacrimal caruncle
Mixture of all surrounding tissues and has the opening of glands in it
What is the punctum
Upper punctum releases tear film into the eye and Lower punctum secretes secretions of glands along with upper punctum
located In the eye lids
The wall of the eyeball is comprised of what layers
1- Outer : Sclera and cornea 2- Middle : Uvea ( vascular ) - choroid - ciliary body - iris 3- inner : retina
What is the cornea
transparent Outer layer covering the iris and pupil made of organized collagen that gives the transparency.
What is the purpose of the Uvea of eye
mediator of nutrition and gas exchange because blood vessels will course through them
What is the retinal layer made of
Nervous tissue
What is the function of the cornea
Protective role and Helps to bend the light coming into the eye ( refract ) .
What is the sclera made of
Tough , dense CT that’s white and opaque. Mainly type 1 collagen fibres. No organization of fibres which gives white apearence.
What is the name of the boundary between the cornea and sclera
Limbus : the zone of transition of epithelium between sclera and cornea
What is the role of the sclera
Provides attachment of the intraocular muscles. Forms outer protective layer.
Anterior sclera and inner surface of eyelid is covered by
Conjuctiva : thin transparent mucus membrane
What is the role of conjuctiva
Prevents microbial entrance into the eye
Explain the Uvea
Pigmented layer to light proof the eye and reduce reflection of light.
- Anterior portion contains smooth muscle of ciliary body and dilator/constrictor of iris
- contains choroid, ciliary body and processes and iris
What is the role of the ciliary body
Muscle regulated tension of the suspensory ligaments of the lens
What is the posterior 2/3 of the avascular layer
Choroid
What is the Clinical relevance of Choroid
Age related macular degeneration :
Blood vessels in choroid have build up of lipid deposits = prevents diffusion of nutrients into the retina
What are the layers of the retina
Two layers
1- anterior 1/3 outer pigmented epithelial layer : single layer of pigmented simple cuboidal cells
2- posterior 2/3 inner neural layer : photosensitive and contains photoreceptor neurons ( cods and cones )
What is the purpose of the outer layer of retina
1- Absorbs lights scattered around eyeball that might affect ability to see.
2- Provide vitamin A for photoreceptors.
3- Help establish blood retinal barrier through tight junctions to regulate movement of solutes and nutrients from blood vessels into retinal tissue
Is the inner neural layer of the retina present in the anterior 1/3
No , only the retinal outer pigmented epithelium is there
What lines over the ciliary body
Retinal outer pigmented epithelium layer
What is the space between the cornea and the iris
The Anterior chamber : filled with aqueous humour
Where is the posterior chamber
space between posterior surface of iris and anterior surface of lens
What structure is from he lens to the optic disc
The vitreous body : a transparent Gell that fills the region posterior to the lens
What are the functions of the nitrous body
1- Contributes to magnifying power of the eye
2- supports the lens
3- hold the layers of the retina in place
What is the fovea
Point of greatest visual acuity
What are the layers of the cornea
5 layers
1- Outer : corneal epithelium SNKE with wound healing capability
2- Bowmans membrane
3- Corneal stroma : CT makes up most of cornea
4- Descemet’s membrane: cellular layer made of thing type 4 collagen
5- Corneal endothelium : simple squamous facing anterior chamber of eye.
What is bowman’s membrane
Basement membrane to corneal epithelium made of CT and If damaged it could lead to scarring which can affect vision
Can severe damage to corneal endothelium be prepared
Only through transplantation
What fluid lies behind the cornea
Aqueous humour filling anterior chamber, between cornea and iris
What layer if damaged in cornea could cause issues to visual acuity
Bowman’s membrane
What is the function of the corneal storm layer
Refract light
What is the basement membrane of the corneal endothelium
Descemet’s membrane
The iris is an extension of the ? located in ?
Ciliary body . located in anterior 1/3 of Uvea
What is the purpose of the iris
Controls how much light the pupil lets in
What is the anterior border of the iris
limiting layer Composed of fibroblasts and melanocytes
What is the posterior surface of the iris
Double layered Pigmented epithelium with contractile properties that cause pupils to dilate and constrict along with muscles in stroll layer of iris
What is the middle layer of the iris
stromal layer of dilator and constricting muscles for pupil
What is the thicker portion of the choroid and why is it thick
Ciliary body. Thick due to layer of smooth ciliary muscle.
What are the ciliary processes
Projections of the ciliary body extending toward the lens
Where is aqueous humour produced
Epithelium lining the ciliary processes
What is the pathway of the aqueous humour
Passes from posterior through the pupil to anterior chambers and then drains through canal of schlemm ( endothelial channels )
Contraction of the ciliary muscle causes what
Relaxation of lens
What is the role of the aqueous humour
1- provides O2 and nutrients to part of lens and cornea
2- helps to assist in corneal reflection of light
What is the trabecular meshwork
Found at junction of iris with cornea which drains all the aqueous humour into the canal of Schlemm
Blockage of drainage of aqueous humour through meshwork could results in what
Intraocular pressure ( glaucoma ) = damage to retina = blindness
What are the layers of the lens
- Outer capsule of type 4 collagen
- layer of cuboidal epithelium on anterior face ( lens )
- centre of tightly packed enucleate cells packed with crystalline ( transparent proteins ) to form lens fibres
Is the lens vascular or avascular
Avascular
Why is transparency of the lens reduced in older individuals
Due to debris collecting in the fibres making it opaque = can cause cataracts
What condition could exacerbate debris in the lens fibres
Diabetes
4 groups of cells in the sensory retina
9 layers of different cell types could be grouped into 4 main categories
1- Photoreceptor neurons : rods and cons
2- conducting neurons : bipolar and ganglion cells
3- association neurons : horizontal & amacrine cells
4- neuroglia cells : muller cells
List the layers of the sensory retina
1- Internal limiting membrane : 2- nerve fibre layer 3- ganglion cell layer 4- inner plexiform layer 5- inner nuclear layer 6- outer plexiform layer 7- outer nuclear layer 8- external limiting membrane : 9- photoreceptors : rods and cons
Where are the cell bodies of the cons and rods ( photoreceptors )
In the outer nuclear layer
Where are the cell bodies of the amacrine , glial and bipolar and horizontal of the retina
Inner nuclear layer
Where is the nucleus of the retinal ganglion cells
Ganglion cell layer
Where do the nerve fibres of the ganglion layer go to
Travel through the nerve fibre layer to the optic disc & optic nerve
What are the plexiform layers (outer and inner ) of the retina
Fibrous layers that contain neuron synapses between axons and dendrites
What is the role of the external limiting membrane e
Separate photosensitive regions ( rods and cons ) from areas of the retina that transmit neurochemical signals
Where are the rods and cons embedded in
Retinal pigment epithelium
What cells form the images in the retina
The rods and cons
What are rods cell
Photoreceptor cells sensitive to light and particularly active in night vision and vision at low light levels
What are cons
Photoreceptor cells that are responsible for high spatial acuity , distinguishing between colours and Higher light levels
List 5 principal regions of rods and cons
1- retinal pigmented epithelium
2- outer segment : captures light in photoreceptor discs and converts to electric signals
3- inner segments containing organelles cell requires
4- Nucleus ONL : hosing nucleus
5- Synaptic bouton : synaptic region
What is the macula
Photoreceptors are localized around the macula. The functional centre of retina.
What is the fovea
Structure in the macula , a small shallow dimple where the cones are concentrated and where most of the light will be directed to.
Where are the rods concentrated
Periphery of the retina except at centre of fovea , where the cons are
What is the blind spot
The break in the retina that is the optic disk
Can the rods detect difference between colours
No
Where is the optic nerve
Point where all the axons form the ganglion cells merge and from the optic nerve. AKA the blind spot
What is the orbiculares muscle
skeletal Muscle in the eyelid
What are the glands that form the tear film
Meibomiam Glands , Apocrine glands , lacrimal glands
Is the cornea vascular or avascular
avascular
How do tears protect the conjuctiva form infection
contain antimicrobial and antibacterial proteins
What is the outer surface of the eyelid made of
SNK epthelium
What are is the purpose of the apocrine sweat glands in the eyelid
add lysozyme and antibacterial agents to the tear film
What is the mucocutaneous junction
Muco : epidermis of eyelid
cutaneous : conjuctiva of eyelid
What is the conjuctiva
Stratified columnar epithelium contains goblet cells that make mucous secretions to add to tear film
What is the tarsal plate
Dense fibroelastic tissue contains glands of meibomian
What are the meibomian glands
Sebaceous glands that secrete lipid rich secretions that prevents tears from evaporating
