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Ocular Physiology > Tears > Flashcards

Tears Flashcards

1
Q

what is the outer layer made up of?

A

lipid (oil)

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2
Q

what is the middle layer made up of?

A

aqueous (water)

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3
Q

what is the inner layer made up of?

A

mucin layer

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4
Q

what issues would occur if no tear layer?

A

cornea epithelium is irregular (due to microvilli) and this disrupts the optical wavefront (blurry image on retina)

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5
Q

function of: lysozyme

A

degrades mucopeptides of bacterial cell wall

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6
Q

function of: B-lysin

A

disrupts integrity of bacterial plasma membranes

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7
Q

function of: immunoglobulin A

A

mediates antigen-specific humoral immunity, marks bacteria for destruction

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8
Q

where is aqueous mostly produced?

A

lacrimal gland in the superior temporal fornix

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9
Q

lipid layer contains:

A

many proteins

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10
Q

large aqueous and mucous layer contains:

A

various proteins and ions (Na+, K+, Cl-)

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11
Q

mucous layer subdivided into:

A
  • mucous laye r

- glycocalyx

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12
Q

source of outer oily layer is:

A

meibomian glands

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13
Q

source of middle aqueous layer is:

A

lacrimal glands (a little by accessory lacrimal glands)

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14
Q

source of inner mucin layer is:

A

goblet cells

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15
Q

definition of glycocalyx:

A

layer of membrane bound mucin attached to epithelial cells

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16
Q

function of glycocalyx:

A

protects epithelium, prevents bacterial from reaching and attacking epithelium

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17
Q

where are goblet cells located and NOT located?

A

goblet cells only in conjunctiva and NOT in cornea

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18
Q

mucous reduces the surface tension of the epithelium from:

A

70 to 40 dynes/cm^2

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19
Q

mucin attaches to epithelium to make the surface:

A

hydrophilic

so water spreads out

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20
Q

sensory stimulation causes what affect on goblet cells?

A

causes goblet cells to release mucous

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21
Q

about how many goblet cells are in an eye?

A

about 1.5 million

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22
Q

most goblet cells are located

A

medially and inferiorly

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23
Q

sources (and %) of aqueous

A
  • lacrimal gland (95%)

- accessory lacrimal glands (5%)

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24
Q

characteristics of aqueous

A

low protein concentration, isotonic solution

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25
Q

functions of aqueous:

A
  • prevents desiccation of epithelium

- bacteriostatic function due to proteins it contains

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26
Q

what can increase aqueous tear production?

A

parasympathetic stimulation

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27
Q

meibomian glands produce what via what type of secretion?

A

oil produced by holocrine secretion

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28
Q

function of oil layer:

A
  • provides a smooth refracting surface

- retards evaporation of aqueous

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29
Q

composition of the oil layer:

A

waxy esters, sterols, cholesterol, lipids (hundreds of different types of substances)

30
Q

location and general appearance of oil layer:

A

on top of aqueous later and looks like oil slick in street (forms colored fringes)

31
Q

thickness of tear film estimate via fine glass fibers was:

A

7-8 microns

32
Q

thickness of tear film estimate via OCT was:

A

3.4 +/- 2.6 microns

33
Q

which layer is thicker in the conjunctiva than in the cornea?

A

mucous layer

34
Q

which layer is thicker in the cornea than in the conjunctiva?

A

aqueous

35
Q

total tear volume

A

8 microns of fluid on the eye

36
Q

entire eye and curl-de-sac can hold a max of ___ before blink

A

50-60 microns

37
Q

tear volume in the superior and inferior cul-de-sac

A

4 microns (about 1/2 of all fluid)

38
Q

tear volume in the tear prism

A

3 microns

39
Q

tear volume in the exposed eye

A

1 micron

40
Q

basal aqueous production rate:

A

1.2 microliters/min

41
Q

aqueous production can go up to ___ microliters/min if stimulated

A

70 microliters/min (reflex-driven tear production)

42
Q

what is a normal tear meniscus height test result?

A

> 0.1 mm

43
Q

what is normal Schirmer tear strip findings?

A

> 10 mm in 5 minutes

44
Q

what kind of skewed result does the sponge method give for tear production?

A

gives low aqueous production rates (0.5 ul/min) probably due to evaporation

45
Q

what is an important finding about changes in tear production discovered in fluorophotometry studies?

A

showed tear production decreases with age

about 20% decrease in 40-53 age group

46
Q

explain how age may affect tear production vs. tear volume

A
  • tear volume on the eye does NOT decrease with age

- tear production does!

47
Q

the most irritating test has the highest tear production rate: which test is this?

A

schirmer strip WITHOUT anesthesia has highest rate

48
Q

performing tests with anesthesia will show ____ tear production rates

A

lower

49
Q

since age dramatically decreases tear production, what is the normal wetting for age 20-29 group?

A

40-50 mL

50
Q

list of medications that can cause dry eye

A

-antihypertensive, glaucoma (beta blockers), antidepressants, decongestants, antihistamines, birth control pills

51
Q

what is unique about stimulated tears for aqueous secretion?

A

stimulated tears are all from the lacrimal gland (none from accessory)

52
Q

in the parasympathetic pathway: receptors on the lacrimal gland are:

A

m3 muscarinic receptors

53
Q

in the parasympathetic pathway: receptors in the lacrimal are located in the:

A

acinar and duct cells of the gland

54
Q

increasing parasympathetic activity of lacrimal gland will ____ tear production

A

increase

55
Q

sphenopalatine ganglion stimulation leads to _____ tear secretion

A

increase

56
Q

increased tear secretion includes

A

water, electrolytes (Na+, K+, Cl-, bicarbonate), regulated protein

57
Q

in the sympathetic pathway, what are the receptors?

A

alpha and beta adrenergic receptors on acinar cells

58
Q

sympathetic stimulation causes and increase in what type of secretion in the tears?

A

increase in PROTEIN secretion

59
Q

what is stage 1 of tear production?

A

acinus-intercalated duct region secretes fluid resembling an isotonic ultra filtrate of plasma

60
Q

what is stage 2 of tear production?

A

ductal segments secrete additional K+ and Cl-

61
Q

what is special about the type of control between the 2 stages of tear production?

A

ions in the tears remain constant regardless of tear production

62
Q

what ion concentrations increase as ultra filtrate travels down duct?

A

K+ and Cl-

63
Q

in tear production, what are the set affects of the Na/K pump and K channel?

A

increase Na+ in interstitial space

64
Q

what does the net increase in Na+ drive?

A

the Na+/Cl- cotransport channel (brings Na+ and Cl- into cell)

65
Q

net effect of Na+/Cl- cotransport is:

A

Cl- concentration in the cell increases

66
Q

definition of constitutive protein secretion

A

proteins that require something external to the lacrimal gland to make it

67
Q

example of a constitutive protein secretion?

A

IgA- dependent on plasma cells in interstitial space around lacrimal gland to make IgA

68
Q

what are the stimuli for regulated protein secretion?

A

parasymp. or symp. results in 2nd messenger system(cAMP, Ca2+) to release stored proteins into the tears

69
Q

definition of regulated protein secretion:

A

proteins made in cells of lacrimal gland are released when stimulus is given

70
Q

about how many proteins in the tears have been identified?

A

200

71
Q

in stimulated flow of tears there is an increase in what substances?

A

immunoglobulin and lysozyme

Ocular Physiology (8 decks)

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