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62 Cards in this Set
- Front
- Back
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where does active secretion performed? relationship to pressure?
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1. location on epithelium cells...NOT CAPILLARIES
2. NOT PRESSURE DEPENDENT |
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what is the turnover rate of aqueous humor
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1. ~2 hours
2. ~2.5 microliters/minute |
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what is pseudofacility
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1. the ultrafiltration component of aqueous humor formation is pressure sensitive, DECREASING with INCREASING IOP
2. a pressure sensitive decrease in inflow appears as an increase in outflow facility |
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what is the affect of carbonic anhydrase inhibitors
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decrease rate of aqueous production
inhibits formation and transport of bicarbonate and hydrogen ions across the pigment and nonpigmented ciliary epithelia...bicarbonate transport affects the transport of other ions, including sodium and chloride |
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what is the affect of beta 2 adrenergic antagonists (beta 2 blocker)
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decrease rate of aqueous production
reduction in NKCC contransport |
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what is the affect of alpha 2 adrenergic agonists
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decrease rate of aqueous production
reduction in... 1. release of endogenous norepinephrine 2. of beta 2 receptors 3. cAMP production 4. NKCC contransport 5. permeability of blood-aqueous barrier |
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what is the affect of adrenergic agonist
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decrease rate of aqueous production
stimulate both alpha and beta receptors might depend on the degree of stimulation of alpha 2 adrenergic receptors, as well as circadian rhythm |
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what drugs DECREASE rate of aqueous production
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1. carbonic anhydrase inhibitors
2. beta 2 adrenergic antagonists 3. alpha 2 adrenergic agonists 4. adrenergic agonists |
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what is the function of the aqueous humor
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1. delivery of oxygen and nutrients to and removal of waste products from avascular intraocular structures
2. high concentration of ascorbic acid serve as an antioxidant, absorbs UV radiation and regulate the GAGs of the TM |
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protein concentration in aqueous humor?
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1. LOW CONCENTRATION OF PROTEINS
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how is the TB involved in regulating outflow
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1. TM is between anterior chamber and schlemn's canal...sense pressure from both compartments through physical and chemical stimuli
2. TM adjusts accordingly |
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how does the TM prevent POAG and what is the relationship with age
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TM is in effect a self-cleaning filter, and that in most of the open-angle glaucomas, the self cleaning function is deficient or at least inadequate to cope with the amount of material present
phagocytic capabilities decrease with age. |
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how are suction cups used to calculate aqueous secretion and outflow
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1. applied to the perilimbal area, theoretically occluding the episcleral veins and thus trabecular outflow from the eye
2. IOP rises abruptly during application of the SC. 3. after the SC has been released, the rate of return to normal IOP gives info regarding outflow a. the higher the pressure rise per minute of SC application, the higher the aqueous secretory rate b. the slower the return to baseline IOP, the lower the outflow facility |
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what are the factors that affect aqueous outflow
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1. resistance increase with age
2. increase in accommodation results in increase in trabecular outflow 3. relaxation of the ciliary muscle increases uveoscleral outflow 4. in POAG, the juxtacanalicular tissue is depleted of hyaluronic acid and there is an accumulation of chondroitin sulfate, which may increase outflow resistance and IOP |
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what is the affect of long term interaction with corticosteriods with respects to IOP
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contribute to increasing outflow resistance in susceptible individuals...INCREASE IOP
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what does prostaglandins do to the ciliary muscles
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1. relaxation, results in less restricted excellular channels between muscle fibers and increased spacing through which fluid might pass
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what affect does prostaglandins have on trabecular outflow
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1. dose-dependent INCREASE of trabecular outflow
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what is maurice lattice theory
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1. the collagen fibrils are arranged in a regular lattice, like a stack of diffraction gratings
2. corneal fibrils diameter is about 20-30nm, inter-fibrillar spacing is about 30nm...therefore, spacing of collagen fibrils is about 60nm center to center 3. exact regular spacing IS NOT required for transparency |
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what are the functions of keratocytes
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1. matrix turnover
2. intracorneal communication 3. reservoir for glycogen (energy source) 4. interlamellar tethering 5. wound healing by producing new matrix |
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what is the distribution scheme of keratocytes
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1. non-uniform distribution
2. ~2.4 million 3. greatest density in the front part and progressively less 4. corkscrew pattern 5. gap junction between cells |
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what are the difference between dermatan sulfate and keratan sulfate
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dermatan sulfate:
1. prefer oxygen-rich environment 2. predominantly in anterior portion 3. more efficient at holding water keratan sulfate: 1. prefer less oxygen 2. posterior portion of cornea 3. absorbs more water, not as efficient as dermatan |
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what is the partial pressure of oxygen in the aqueous humor
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55mmHg
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the healthy corneal epithelium has an electrical potential difference across it of...
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15-20mV
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describe the corneal epithelial barrier
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TIGHT BARRIER
1. limited permeability to water, cations/anions 2. stops water influx into the cornea from the tear film...because of high resistance |
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what happens to the corneal with exposure to cytotoxins and desiccation
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1. thinning/increased evaporation
2. if its really bad, there will be a great increase in net fluid influx which can not be compensated by evaporation...resulting in increased corneal hydration (edema) |
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what is the major transport protein? where is it found?
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1. Na/K/ATPase
2. basolateral membrane of a single corneal endothelial cell |
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at what point does the leak rate cross the decrease in pump site
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500 cells/nm
lower than 500 results in corneal edema |
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what is normal hydration of corneal tissue
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3.55mg H2O/mg of dry tissue
78% water |
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what is the swelling pressure of the normal corneal stroma
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40-60mmHg
1. it is easy to squeeze water out of a more hydrated stroma and so a low swelling pressure will be recorded IMAGE A SPUNGE |
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what is the main source of glucose in the epithelium and endothelium?
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aqueous humor
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what are the three pathways to get some glucose to pyruvate
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sorbital pathway
glycolysis hexose monophosphate shunt |
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krebs TCA cycle
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1. aerobic conditions
2. 38 ATP 3. consumes oxygen |
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how is arachidonic acid metabolized during hypoxia/inflammation
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cytochrome P450
produces two eicosanoids: 12(R)HETE 12(R)HETrE |
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what is the relationship between scarring and the corneal epithelium
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1. only injuries deeper than epithelium will result in scarring
2. injury limited to the epithelium will heal without scarring |
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where is fibronectin and intergrin located in respects to the cell
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fibronectin: extracellular
integrin: intracellular |
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what happens to the cornea during hypoxia
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lactic acid accumulates in the stroma, increasing osmotic pressure and hydration. there is more edema in the posterior stroma due to the arrangement of the lamellae
1. efflux of endothelium stays the same during hypoxia 2. increase in passive diffusion |
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1. average IOP
2. pressure of suprachoroidal space (between uvea and sclera) |
1. 15mmHg
2. 2mmHg lower than IOP |
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hydration in the lens
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average ~66%
1. capsule: 80% 2. dense nuclear region: 63% 3. cortex: 68% |
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what type of crystallin is found in the nucleus? why
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1. gamma crystallins
2. synthesized in the embryonic lens, so more gamma crystallin is found in the nucleus than in the cortex 3. MW 21000 |
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concentration of free amino acids in relation to lens, aqueous, vitreous, and plasma
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concentration of free amino acids in the LENS is higher than that in the aqueous, vitreous, or plasma
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oxygen consumption in the lens
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LOW!!!
oxygen consumption from highest to lowest: 1. epithelium 2. cortex 3. nucleus |
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ATP consumption in the lens
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10%: protein and glutathione synthesis
90%: active transport mechanisum, cell division, biochemical pathways to protect the lens from oxidative damage, and maintenance of cellular homeostasis |
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what is the rate limiting factor in glucose metabolism
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low levels of HEXOKINASE...first enzyme of the glycolytic pathway
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what is the reactant and product for the sorbitol pathway
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R: glucose
P: fructose 1. glucose aldose reduction 2. sorbitol polyol dehydrogenase 3. fructose |
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calcium levels inside the lens...
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the level of calcium inside the lens is significantly lower than that in the aqueous humor or vitreous
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what happens to potassium and sodium in relation to the "pump leak" system
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1. sodium more concentrated in posterior cortex
2. potassium more concentrated in the anterior cortex |
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what is the purpose of glutathoine
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1. reductive factor
2. prevent from harmful oxidation |
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what is the relationship between rate of diffusion of glutathione and AGE
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the rate of diffusion of glutathione between the superficial and deeper layers DECREASED with AGE
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what is the mechanism in which glutathione prevent harmful oxidation
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1. GSH binds with harmful oxidized sulfhydryl group
2. forming GSSG 3. GSSG diffuse to superficial layer of lens and is reduced to GSH (enzyme: GSH reductase) 4. NADPH used at cofactor, sourced from hexose monophosphate shunt |
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electrolyte composition in relation to AGE
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AGE...
1. increases: sodium, calcium, and chloride 2. decreases: potassium (or remains the same) |
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where is the vitreous most likely to herniate through the anterior chamber
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PATELLAR FOSSA
anterior vitreous is thinnest here |
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what type of collagen is in the vitreous
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TYPE II
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concentration of amino acids in vitreous
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1. higher concentration in the anterior vitreous than posterior vitreous, possibly due to utilization of amino acids by the retina
2. 1/5 of plasma levels |
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concentration of ascorbic acid in vitreous
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1. 9X greater than plasma
2. actively transported into the vitreous by the ciliary body 3. acts to absorbs UV light and as a free radical scavenger |
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what are the functions of the vitreous
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1. oxygen tension lowest in the central region
2. metabolic respiratory of wastes and short term retinal needs 3. movement of solute and solvent within eye 4. 50% of the water is turned over in 10-15 minutes 5. must maintain barrier to cell invasion to maintain transparency 6. shock absorber |
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where is the vitreous most likely to herniate through the anterior chamber
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PATELLAR FOSSA
anterior vitreous is thinnest here |
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what type of collagen is in the vitreous
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TYPE II
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concentration of amino acids in vitreous
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1. higher concentration in the anterior vitreous than posterior vitreous, possibly due to utilization of amino acids by the retina
2. 1/5 of plasma levels |
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concentration of ascorbic acid in vitreous
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1. 9X greater than plasma
2. actively transported into the vitreous by the ciliary body 3. acts to absorbs UV light and as a free radical scavenger |
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what are the functions of the vitreous
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1. oxygen tension lowest in the central region
2. metabolic respiratory of wastes and short term retinal needs 3. movement of solute and solvent within eye 4. 50% of the water is turned over in 10-15 minutes 5. must maintain barrier to cell invasion to maintain transparency 6. shock absorber |
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what does epinephrine do to IOP? HOW??
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DECREASE IOP!!!
1. INCREASE outflow through trabecular pathway 2. INCREASE outflow through uveoscleral pathway 3. DECREASE aqueous productions |
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what does epinephrine do to IOP? HOW??
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DECREASE IOP!!!
1. INCREASE outflow through trabecular pathway 2. INCREASE outflow through uveoscleral pathway 3. DECREASE aqueous productions |
