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Ocular Physiology > Lacrimal System and Conjunctiva > Flashcards

Lacrimal System and Conjunctiva Flashcards

1
Q

what is the main provider of the aqueous secretory component of the tear film

A

the main lacrimal gland

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2
Q

where is the main lacrimal gland located

A

in the fossa for the lacrimal gland (anterio-lateral orbit)

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3
Q

what divides the lacrimal gland into orbital and palpebral lobes

A

the lateral horn of the levator and extensions of Mullers muscle

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4
Q

which lobe of the lacrimal gland, orbital or palpebral, is larger

A

the orbital, it lies behind the orbital septum and above the levator aponeurosis

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5
Q

what is the normal color of the lacrimal gland

A

pinkish-gray

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6
Q

what is the lacrimal gland made up of (drains)

A

many acini that drain into larger tubles

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7
Q

what type of tissue are acini made of

A

basal myoepithelial cell layer with inner columnar secretory cells

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8
Q

why is it important that acini are myoepithelial cells

A

it requires muscle movement to allow the contents to be drained

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9
Q

when does the lacrimal gland begin to develop

A

near the third month of fetal life

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10
Q

when does the lacrimal gland begin functioning after birth

A

it may be as long as 2 months

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11
Q

when do newborn babies start to produce tears

A

2 weeks after birth

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12
Q

if the lacrimal gland doesn’t produce tears in infants, what keeps their eyes from drying out

A

their accessory glands are functional

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13
Q

what are the secondary providers of the aqueous secretory component of the tear film

A

glands of krause and wolfring

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14
Q

what was the historical perspective of the accessory glands

A

that they were for the main secretion (basal tearing) and the lacrimal gland was for reflex tearing

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15
Q

where are the glands of wolfing located

A

in the tarsal plate of the eyelid

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16
Q

which lid, upper or lower, has more accessory glands

A

the upper lid

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17
Q

what are trilaminar tears

A

3 layers: aqueous, mucus, and lipid

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18
Q

where are the glands of krause located

A

in the conjunctival fornix

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19
Q

what are the 3 arterial supply sources to the lacrimal gland

A

the lacrimal branch of ophthalmic artery, branch of the infraorbital artery and the recurrent meningeal artery

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20
Q

what is the sensory innervation to the lacrimal gland

A

the lacrimal branch of the trigeminal nerve (5)

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21
Q

what other ocular structure has innervation from the trigeminal nerve

A

the cornea

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22
Q

what is the order of the 3 layer structure of the tear film

A

outer lipid layer, middle aqueous layer, inner mucous layer

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23
Q

what is the primary source of oxygen to cornea

A

the tear film (the cornea is avascular)

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24
Q

besides supplying oxygen to the cornea, what are the other functions of the tear film

A

lubricant between lids and ocular surface, remove foreign bodies, debris, and has antibacterial proteins for protection

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25
Q

where does the lipid layer of the tear film come from

A

meibomian glands and gland of zeiss

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26
Q

where does the aqueous layer of the tear film come from

A

lacrimal gland, fornix accessory lacrimal gland (krause) and palpebral accessory lacrimal gland (wolfring)

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27
Q

where does the mucus layer of the tear film come from

A

goblet cells, epithelial cells, and lacrimal gland (very little)

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28
Q

how thick are each of the 3 layers of the tear film

A

lipid is 0.1 microns, aqueous is 7 microns, and mucus is 0.02-0.05 microns

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29
Q

what type of glands are the meibomian glands

A

sebaceous glands that secrete lipids onto the tear film

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30
Q

what is holocrine secretion (meibomian glands)

A

when the discharged secretion contains the entire secreting cells laden with the secretory material

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31
Q

what releases the meibomian material from the ducts onto the tear film

A

when you blink

32
Q

what are the different types of lipids in the meibomian material

A

wax monoesters, sterol esters, hydrocarbons, triglycerides, diglycerides, free sterols (cholesterol), free fatty acids and polar lipids (phospholipids)

33
Q

what are 2 possible steps where regulation could occur for meibomian gland secretion

A

by controlling the rate of lipid synthesis in the endoplasmic reticulum and by regulating the rupture of alveolar cells

34
Q

is the regulation of meibomian secretion known

A

no it is not known but there are possible suggestions

35
Q

can androgen sex steroids regulate synthesis and secretion of meibomian glands

A

yes (testosterone)

36
Q

what might neurotransmitters do to regulate meibomian glands

A

(from the nerves surrounding the acini) alters the synthesis or rupture cells

37
Q

how could meibomian secretion be neural regulated

A

vascoactive intestinal peptide (VIP) and neuropeptide Y (NPY) found in parasympathetic nerves

38
Q

what are the proteins that are in the aqueous layer of the tear film

A

lysozyme, lactoferrin, lipocalin, SlgA, as well as epidermal growth factor, several types of growth factors (TGFs) and interleukins

39
Q

what type of gland is the lacrimal gland

A

a tubuloacinar exocrine gland

40
Q

why are artificial tears only a temporary fix for dry eyes

A

they are limited because they do not have growth factors

41
Q

what is the final tear fluid a mixture of

A

sodium chloride rich fluid

42
Q

what are the 3 things that are secreted in the aqueous layer

A

proteins, electrolytes, and water

43
Q

what happens to the corneal transparency if eyes become severely dry

A

it may lose transparency

44
Q

where does the final source of electrolytes and water in the aqueous layer come from

A

the conjunctiva

45
Q

what is the mechanism for conjunctival electrolyte and water secretion

A

conjunctival Cl- secretion accounts for most of the conjunctival active transport (similar to the lacrimal gland)

46
Q

what is a mucin

A

collection of glycoproteins (protein backbone and carbohydrate side chains- at least 50% carbs) secreted by goblet cells

47
Q

what is the major source of the mucus layer of the tear film

A

the conjunctival goblet cells

48
Q

what activates the secretion of the goblet cells

A

activation of sensory nerves

49
Q

what is the secondary source of the mucus layer

A

stratified squamous cells of conjunctiva and corneal epithelium

50
Q

what lines the superior and inferior canaliculi

A

stratified squamous epithelium

51
Q

what muscle surrounds the superior and inferior canaliculi

A

the orbicularis oculi

52
Q

what is the size of the opening of the punctum

A

0.3 mm

53
Q

what is the diameter of the canaliculi

A

0.5-1.00 mm

54
Q

about how long are the superior and inferior canaliculi

A

10 mm

55
Q

what percentage of the population has a common canaliculi

A

90%

56
Q

what is present at the opening of the nasolacrimal sac

A

Hasner’s valve (mucosal flap)

57
Q

what percentage of the tear volume is lost to evaporation

A

10-25%

58
Q

what is the lacrimal pump theory

A

contraction of the pretarsal orbicularis muscle fibers during eyelid closure compresses and shortens the canliculi- the shortening pumps tears towards the lacrimal sac (Jones, Jones, and Wobig)

59
Q

due to gravity which punctum drains more of the tears

A

the inferior punctum

60
Q

how would facial paralysis affect tear drainage

A

it would cause epiphora (orbicularis oculi muscle isn’t closing the eye)

61
Q

what is the volume of tears drained per blink

A

about 2 ml

62
Q

does the lacrimal excretory system function above or below capacity

A

it usually functions far below capacity

63
Q

does a single blink transport more tears than produced by basic secretion in 1 min

A

yes

64
Q

does gravity increase or decrease lacrimal drainage

A

increases

65
Q

when does siphoning by the lacrimal sac occur

A

during relaxation of the blink

66
Q

when do the tears come down from the lacrimal gland

A

with each blink, as the eye is closing a fresh supply of tears is brought down and zippered across the eye

67
Q

what are 3 situations that would lead to insufficient tear layer

A

atrophy of lacrimal gland, increase in age, and compromised innervation

68
Q

what causes dry eye complaints in contact lens wearers

A

insufficient tears, poor quality or decreased tear break up time, infrequent blinking, incomplete blinking, low osmolarity of tears, or blepharitis

69
Q

does tear production vary with gender

A

no

70
Q

what is the Jones test

A

a test used to check for how open the lacrimal drainage system is

71
Q

what symptom do patients have where you would do a Jones test

A

epiphora

72
Q

what is a positive result of the jones test

A

if the patient has the dye in their nose

73
Q

what does a positive result of the jones test mean

A

the epiphora was caused by excessive tearing or primary hypersecretion

74
Q

what does a negative jones test mean

A

there is a blockage and further investigation is needed

75
Q

what is a secondary jones test

A

using a syringe to inject saline into the punctum and canaliculi

76
Q

what did Doane emphasize for the drainage of tears

A

the compression of the canaliculi (lesser extend in the nasolacrimal sac during eyelid closure)

77
Q

what did Doane’s model of siphoning involve

A

siphoning by the lacrimal sac occurs during relaxation of the blink, rather than during closure as suggested by jones

Ocular Physiology (6 decks)

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