Unit 1 A&P Flashcards
What are the 5 functions of the choroid?
Light absorption
Thermoregulation
Nutrition to outer 1/3 of retina
Modulation of IOP via blood flow control
Drainage of aqueous flow via uveo-scleral pathway
Which arteries feeds the choroid?
Anterior and posterior ciliary arteries
What are the 4 layers of the choroid (outside - in)
- Haller’s
- Satler’s
- Choriocapillaris
- Bruch’s
(historic sports car boys)
What are the 5 layers of Bruchs (outside - in)
- basement membrane of choriocapillaris
- outer collagenous zone
- central band of elastic fibres
- inner collagenous zone
- basement membrane of RPE
What 4 age changes occur to Bruch’s?
Calcification of elastic fibres
Increased cross-linking of collagenous fibres
Increased turnover of glycosaminoglycans
Fat accumulation
What are the layers of the sclera? ( outside - in)
- episclera
- scleral stroma
- lamina fusca
What is the ideal entry point for retinal surgery and why?
Pars plana as there is no overlying retina
What size is the macula and where is it?
What size is the optic disc?
5mm in diameter,
3mm temporal to OD
OD is 1.8 x 1.7 mm
What diameter is the fovea?
1.5mm
Which artery feeds the inner 2/3 of the retina and from where does it originate?
Central retinal artery which is the first branch of the ophthalmic artery.
What are the names of the 3 layers of capillaries that service the retina?
Radial (peripapillary capillaries)
Superficial capillaries in the ganglion and nerve fibre layers.
Inner nuclear layer, deep dense capillaries.
In which quadrant do most A/V crossings occur and why?
Temporally because nasal vessels tend to follow a straighter route.
In which patients is reduced blood flow common?
Glaucoma,
AMD
Diabetic retinopathy
What speed do retinal capillaries circulate?
172mls/100g retina/min
What speed does blood flow in the choriocapillaris?
1280mls blood/100g retina/min
How is retinal blood flow regulated?
Autoregulated and governed by metabolic need.
Name the 10 retinal layers (outer - innter)
- RPE
- Inner and outer segments of photoreceptors
- External limiting membrane
- Outer nuclear layer
- Outer plexiform layer
- Inner nuclear layer
- Inner plexiform layer
- Ganglion layer
- Nerve fibre layer
- Inner limiting membrane
What is the external limiting membrane made up of?
Fusion of muller cells
What is the inner limiting membrane made up of?
Muller cell foot plates
What is the outer nuclear layer made up of?
Nuclei and cell organelles of the photoreceptors
What is the outer plexiform made up of?
- Bipolar cells (radial patter,n on or off)
- Horizontal cells (used in visual signal integration)
- Amacrine cells (modulate bipolar and photoreceptor signals)
- Ganglion cells
- Muller cells
What is the vitreous made of?
- 99% water
- Hyaluronic acid
- Soluble proteins
- Ascorbic acid
- Type 2 collagen fibrils
Where is vitreous attached to the retina?
Pars plana
Ora serrata
Optic disc
Macula Along large retinal vessels
What are the steps the 11-cis componant of rhodopsin undergoes on exposure to light?
- all trans retinal
- all trans retinol (then moves to RPE)
- trans retinyl esters
- RPE65
- cis-retinol
Describe the activation cycle following the conversion of 11-cis retinal - all trans retinal?
This activates transducin which activates PDE which converts cGMP into normal GMP which closes the sodium channels.
What is the polarity of photoreceptors in their resting state compared to normal cells and in light conditions?
-57mV (-78 in other cells)
How many rods and cones are there?
60 million cones
120 million rods
What are the 7 functions of the RPE
- Electrical homeostasis
- Cell regeneration after surgey
- Visual pigment synthesis
- Phagocytosis
- Maintenance of retinal adhesion
- Control of fluid and nutrients into the subretinal space
- Synthesis of growth factors i.e. VEGF
What pigments are found in the RPE?
Lipofuscin
Melanin
Where does lipofuscin come from
Aged or damaged photoreceptors
Which pigment is responsible for the intrinsic fluorescence of the fundus?
Liposfucin
Why is the aged fundus less pigmented?
Melanin is contained within melanosomes which fuse with lysosome and breakdown with age.
Which cones respond to short, medium and long wavelengths?
blue, green, red
What are the hyper reflective lines on oct?
RPE/Bruchs
Inderdigitation zone
Ellipsoid zone
External limiting membrane
Name the oct layers from choroid to inner limiting membrane?
Haller
Sattler
Choriocapillaris
Rpe/bruch’s
Interdigitaption zone
Photoreceptor outer segs
Ellipsoid zone
Myoid zone
External limiting membrane
Outer nuclear layer
Outer plexiform layer
Inner nuclear layer
Inner plexiform layer
Ganglion cell layer
Nerve fibre layer
Inner limiting membrane
Where does the interdigitation zone originate from ?
Where the rpe cells encase the outer segment of the photoreceptor.
where does the myoid zone originate from?
Golgi apparatus beyond the mitochondria on the inner segment
Where does the ellipsoid zone originate from?
The mitochondria on the inner segment of the photoreceptor
