Eye Anatomy, Phototransduction Flashcards
(38 cards)
Describe the development of the eye -
What happens at Week 4
Eye development begins @w4.
Depression in the neural fold - OPTIC SULCUS.
on each side an OPTIC VESICLE grows out from the prosencephalon (diencepthalon)
Describe the development of the eye -
the optic stalk connects the optic vesicle of each side. What is the optic stalk?
Optic stalk is the optic nerve
Describe the development of the eye -
What happens at week 5
@W5 optic esicle folds on itself to form a two layerd optic cup, which partly envelopes the lens vesicle (derived from surface ectoderm)
Describe the development of the eye -
What happens at W6
At week k6 the lens vesicle is pinched off, and the remaining surface ectoderm has begum to form the epithelial covering of the cornea.
The outer layer of the 2 layered optic cup witll form the RETINAL PIGMENTAL EPTIHELIUM
The inner layer will form the NEURAL RETINA
What are the three tissue layers of the eye?
Fibrous outer layer
Uvea (middle layer)
Retina (neural layer)
What is in the fibrous outer layer?
Sclera: site of attachment of extraoccular muscles muscles (continues posteriorly at sheath of optic nerve)
Cornea: anterior part of sclera- innervated by V1
Conjunctiva: continuous with outer laer of cornea, inner surface of eyelids
What is in the middle layer?
Choroid: branches of anterior and posterior ciliary artieres
Ciliary body: w suspensory ligament of lens and ciliary muscle
Iris
What is in the Internal Retinal layer
Neural (optc retina)
Retinal pigmented epithelium
Where is the anterior chamber and what does it ave in it?
Anterior to the iris! contains aqueous humour - watery similar to CSF
Where is the posterior chamber and what does it have in it?
between iris and lens: aqueous humour
Where is the posterior compartment and what does it have in it?
Vitreous humour! thick and gel like
what is the drainage of the eye?
Canal of Schlemm (at corneoscleral junction) -> ciliary vein -> ophthalmic vein -> cavernous sinus
What is a glaucoma?
Problem with drainage, causing increased intraocular pressure -> decreased retinal blood flow -> interferes with axonal transport in optic nerve -> retinal damage and loss of vision
explain the Corneal blink reflex
Sensory receptor/corneal nociceptor —-> V1 ciliary nerve – trigeminal ganglion – spinal trigeminal tract -< synapses in the spinal trigeminal nucleus (bilateral projection -< facial motor nucleus — travels via CNVII (zygomatic and temporal branches) —< orbicularis oris
How does the LENS increase focusing power
By contraction of ciliary muscles which causes loosening of tension on suspensory ligament -> lens becomes more curved or ‘thick’
What are the
parasympathetic
sympathetic components affecting the IRIS
Parasympathetic causes constriction on the iris through sphincter pupillae (CN3)
Sympathetic DILATION: hypothalamus -> spinal cord -> T1 ventral nerve root -> superior cervical ganglion -> dilator pupillae
What is the cellular composition of the retina ? Name all of the layers
‘In New Generations, It Is Only Ophthalmologists Examining Patients Retina’ pathway of light 1-..
- Inner Limiting Membrane
- Nerve Fibre Layer
- Ganglion cell layer
- Inner plexiform lyer
- Inner nuclear layer
- Outer Plexiform layer
- Outer Nuclear Layer
- External limiting membrane: MULLER cells (specialised glial cells)
- Photoreceptor layer: rods and cones
- Retinal pigmented epithleium
What is the blood supply of the orbit?
Branches of the OPHTHALMIC ARTERY (branch of ICA)
- ciliary arteries in choroid - outer layers of the retina
- central retinal artery - inner layers of the retina
What is your blind spot?
Where axons of the retinal ganglion cells exit as the optic nerve; where light falls: there are no photoreceptors to pick it up.
blindness is not percieved, information is filled in
What is the FOVEA?
Spot in the retina directly in the line of vision- it is a thin tissue layer which is
- rich in CONES
- Located in macula lutea
- Directly in line with the visual axis
- Highest acuity
- Axons of cones take a slanted course
What is the function of the pigmented epithelium?
Absorption of light
Phagocytosis of portions of outer segment receptor cells
Photoreceptor cells have an:
OUTER and INNER segment. What are the function of each?
- cell body
- synaptic terminal
OUTER segment: membranes are continuously sloughed off - stacks of membranes filled with RHODOPSIN (visual pigment protein which captuures light photons) . Site of visual TRANSDUCTION
INNER SEGMENT: mitochondria: energy for transduction and synthesis of inner segments
What are the functions of RODS
DIM LIGHT
120 million
Rods responses are SLOW and HIGHLY SENSITIVE- can only respond to moonlight .
All contain RHODOPSIN- cant discriminate colour
What is the function of CONES
COLOUR< LIGHT< SPATIAL DETAIL
Low sensitivity.
6 million
Efficient for: high acuity, colour vision, require more light.
Less visual pigment brief single photon responses which makes them faster
