eye Flashcards
what are sensory organs
specialised organs providing interrelation between CNS and external and internal environment
what does a sensory analyser consist of
sensory organ - peripheral part
nerves - intermediate part
brain - different centres for analysis
where is the eye ball located
- peripheral part of visual analyser located in bony orbit
what is the function of the eyeball
- protects and supports photoreceptors
- gather, focus and process light into precise images
what are the 3 layers of the eyeballl
- external/ tunica fibrosa - sclera and cornea
- middle/ tunica vasculosa - choroid, ciliary body and iris
- inner - pigment epithelium and retina propria
what is the sclera
- soberest posterior 5/6 of the eyeball and forms white dense connective tissue
- moderate amount of ground substance
- few fibroblasts
what are the layers of the sclera
- episclera
- stroma/ sclera proper
- suprachoroid lamina/ lamina fusca
describe the episclera
- loose connective tissue
- has fibroblasts, macrophages, lymphocytes and vessels
describe stroma/ sclera proper
- strong irregular collagen fibres
- sparse fibroblasts
- low vessel content
describe suprachoroid lamina/ lamina fusca
- connects sclera to choroid
- loose connective tissue and melanocytes
describe the cornea
- transparent and colourless
- avascular
- covers anterior 1/6 of eyeball
what are the layers of the cornea
- anterior epithelium - stratified non keratinised
- anterior elastic lamina - collagen fibres
- stroma - lamellae and collagen 1 and 5 fibres
- posterior elastic lamina - collagen 7 fibres
- endothelium - simple squamous or low cuboidal
describe the middle layer/ chorioid proper
- located in posterior 2/3 of eye
- loose connective tissue with numerous vessels and melanocytes forming black layer
what are the layers of the choroid proper
- suprachroidal lamina
- vascular lamina
- choriocapillary lamina
- basal lamina
describe the suprachoroidal lamina of chorioid proper
- loose connective tissue
- melanocytes and fibroblasts
describe the vascular lamina of the choroid proper
- arteries and veins
- collagen and elastic fibres
- fibroblasts and melanocytes
describe the choriocapillary lamina of the choroid proper
- small fenestrated capillaries that nourish the outer retinal layer
describe the basal lamina of the choroid proper
- eosinophilic layer
- separates choroid from retina
- elastic and collagen fibres
what are the contents of the ciliary body/ middle layer
- ciliary muscle
- ciliary processes
describe ciliary processes
covered by epithelium
secretes aqueous humour into posterior chamber
what are the 2 layers of the ciliary epithelium
- non pigmented epithelium
- pigmented epithelium
describe the ciliary stroma
- smooth muscle
- fenestrated capillaries
what are the 3 functional portions of the ciliary muscle
- outer longitudinal or meridional
- radial
- circular
why is the ciliary muscles important
contraction and relaxation alter the convexity of the lens which is required for focusing on near and far objects
describe the iris
- extension of the chorioid in front of the lens
what does the smooth muscle of the iris form
sphincter pupillae and dilator pupillae
what are the layers of the iris
- stroma - vascularised connected tissue
- anterior pigment myoepithelium
- posterior pigment epithelium
describe the structure of the lens
- lens capsule - contains glycoproteins and microfilaments
- sub capsular epithelium - simple cuboidal
- lens fibres - highly differentiated cells
what happens when lens fibre cells loose their nuclei
elongated fibres fill with proteins crystalline and filensin
what is accommodation
the ability of the eye to change its focus from distant to near object
- keeps objects in focus on the retina
what are the 3 chambers of the eye
- anterior chamber
- posterior chamber
- vitreous space
describe the anterior chamber of the eye
space between cornea and iris of the lens
describe the posterior chamber of the eye
- lies between the iris and lens
- contain aqueous humour that flows from the posterior chamber to the anterior chamber via the iris
describe the vitreous space
- lies between the posterior surface of the lens and retina
- filled with transparent gelatinous substance (vitreous body)
what does the vitreous body consist of
99% water
collagen
hyaluronic acid
what are the structure components of the retina
- pigement epithelium
- supporting cells
- neurons
what are the portions of the retina
- posterior optic part
- anterior non visual part
what is the ora serrata
saw like boarder between the blind and optic parts of the retina
what is the 3 part chain of neurons in the retina
- photosensitive cells - rods and cones
- bipolar neurones - connects cones and rods to ganglion cells
- multipolar ganglion cells - forms the optic nerve
what are the 10 layers of the retina
1) pigmented epithelium - rests on brunch membrane
2) photosensitive layer - dendrites of rods and cones
3) outer lining membrane - outer ends of muller cells
4) outer nuclear layer - photosensor neurons - rods and cones
5) outer plexiform layer - synaptic connections between rods and cons and bipolar neuron
6) inner nuclear layer - cell bodies of bipolar neurons
7) inner plexiform layer - synaptic connections between bipolar cells and ganglion neurons
8) ganglion cell layer - cell bodies of ganglion neurons
9) optic never fibres - forms optic nerve
10) inner limiting membrane - inner ends of muller cells
why is the retina inverted
light has to pass through several inner layers before reaching the photoreceptors
what is the function of rods
accept light signals of low intensity and is responsible for black and white vision
what is the function of cones
sensitive to bright light and provides colour vision
describe rod cells
- elongated, cylindrical bipolar cells
what are the regions of rod cells
- inner and outer segments - separated by cilium
- nuclear region
- synaptic region
what is the outer segment of rod cells composed of
numerous flattened membrane discs containing rhodopsin which is a visual pigment
what does the inner segment of rod cells consist of
nucleus, mitochondria, ER and polyribosomes
what does the inner segment of cone cells consist of
ellipsoid - lipid droplet and mitochondria
what does the outer segment of cones cells consist of
stacked membranous half disks containing visual pigment iodospin
what are horizontal cells
associated with multipolar neurons
establish connecting between different photoreceptors
what are amacrine cells
establish contact between ganglion cells
what are muller cells/ retinal gliocytes
elongated cells extending through all of the retina
what is the function of muller/ retinal gliocytes
- structural support
- mediate the transfer of essential metabolites
what is the macula lutea
yellow spot in the retina with a shadow depression called fovea centralis
what is the bulbar conjunctiva
connected to the corneal epithelium on the surface of the eyeball
what is the palpebral conjunctiva
continues to the posterior surface of the eyelid
connects to the skin at the free boarder of the eyelid
what are the contents of the subconjunctival layer
- lymphocytes
- lymph nodes
- accessory lacrimal glands
what is the blind spot
where the optic nerve and blood vessels leave the eyeball giving a lack of light detecting photoreceptors
