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Neural Biology 1 > eyelid and conjunctiva > Flashcards

eyelid and conjunctiva Flashcards

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1
Q

what is the ocular adnexa ?

A

is a collective term for ocular appendages
. eyelids
. conjunctiva
. lacrimal system

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2
Q

what is the lacrimal system responsible for ?

A
  • tear production and tear drainage
  • protective/supportive role
  • maintaining clarity of cornea and contributing to the protection of the ocular surface
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3
Q

what is the position of the eye within the orbit ?

A
  • the eye tends to adopt an anterior position

- eyes adopt a relatively forward position and protruding beyond the lateral margins of the orbit

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4
Q

what are the two parts of the eyelid ?

A
  • orbital part which sits just below the eyebrow

- tarsal part - contains the tarsal plate

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5
Q

what happens to the folds around the eye ?

A
  • they become more pronounced with age
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6
Q

what are the two predominant folds of the eye ?

A
  • superior palpebral sulcus - top of tarsal plate - where upper eyelid folds - represents the separation between the orbital and the tarsal part
  • inferior palpebral sulcus
    . below that marks the borders of the orbital cavity - we have lateral fold ( Malar sulcus ) and one medially on the nasal side ( nasojugal sulcus )
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7
Q

what is the space between eyelids ?

A

palpebral aperture

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8
Q

what are the two angles of the eye where the two eyelids meet laterally and medially ?

A
  • outer canthus - lateral point - at which the two eyelids come together
  • inner canthus - equivalent on the medial side
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9
Q

what is one of the features of inner canthus ?

A

presence of these two structures
- plica semilunaris - sits lateral to the caruncle - fold of mucosa

  • caruncle - mound of mucosal tissue that sits most medially
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10
Q

what is conjunctiva ?

A

mucous membrane which both lines back surface of the eyelid and covers the white of the eye up to its junction with the cornea which is known as the limbus

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11
Q

what is the limbus ?

A

term we use for the junction between cornea and sclera

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12
Q

what is arising from the anterior border of both eyelids ?

A

eyelashes - we can see two or three rows of eyelashes that emanate from anterior border of both eyelids

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13
Q

what is caruncle ?

A
  • mound of mucosal tissue

- contains a lot of goblet cells but doesn’t have any specific function

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14
Q

what are the eyelids ?

A

the eyelids are two moveable folds of the skin

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15
Q

what is the function of eyelids ?

A
  • they are largely their for protection
  • they serve several important functions
    1. acting as occluders shielding the eyes from excessive light
    e. g. when looking at the sun
  1. blink reflex affords protection against injury
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16
Q

what is the purpose of periodic blinking ?

A
  • the purpose of periodic blinking is the spreading of the tear layer
  • forms a tear film of uniform thickness during the upturn phase of each blink
  • blinking is important for tear drainage
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17
Q

how many times do we blink per minute ?

A

10-12 times per minute

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18
Q

what is difference between upper and lower eyelid ?

A
  • upper eyelid is larger and more mobile

- lower eyelids displays a medial movement during blinking - moves laterally rather than up and down

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19
Q

how many rows of lashes emerge from the anterior border of the lid margins ?

A
  • 2-3 rows of lashes emerge from the anterior border of the margins
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20
Q

what does eyelid position alter with ?

A
  • eyelid position alters with eye gaze

- close coordination between eye movement and lid position

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21
Q

what happens when we look upward ?

A
  • the upper eyelid is retracted so that increases the field of view in the up case
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22
Q

what happens when we look downwards?

A
  • the lower eyelids retracts and pulls down - which increase field of view in lower field vision
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23
Q

where are meibomian gland opening ?

A
  • meibomian gland openings are (30-40) located along the lid margins - which sit in upper and lower eyelid
  • located just anterior to the mucocutaneous junction
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24
Q

what is the junction between eyelid skin and conjunctiva ?

A

mucocutaneous junction

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25
Q

what is anterior to to the mucocutaneous junction ?

A
  • thinly keratinised skin - we also see the openings of the meibomian gland
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26
Q

what is the grey line located anterior to the meibomian openings ?

A
  • grey line located anterior to the meibomian openings marks the location of Riolans ( part of orbicularis oculi ) muscle and is an important surgical mark- its where they need to split the eyelid down the middle - that makes an incision bloodless as it it tend to avoid the major blood vessels within the eyelids
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27
Q

what is the function of eyelashes ?

A
  • tend to be effective at trapping dust and debris and they tend to be coated with oily substance that tends to make them quite sticky helping them collect dust and debris and preventing it from entering the eye
  • equipped with sensory receptors that initiate blink reflex
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28
Q

what is the lid wiper region at the eyelid ?

A

represent the point at which the eyelid margin contact the globe - it extends about 0.6mm from the mucocutaneous junction to the subtarsal fold

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29
Q

what is the function of lid wiper ?

A

region at the eyelid margin responsible for spreading tears during blinking

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30
Q

why do alteration of the lid wiper happen for contact lens wearers ?

A

alterations of the lid wiper region due to increased friction between this region and ocular or contact lens surface this is called lid wiper epitheliopathy which is disruption of surface epithelium

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31
Q

how can we see lid wiper ?

A
  • stains with dyes such as fluorescein or lissamine green

- length and width of staining correlates with symptoms of dry eye ( particularly in subjects wearing contact lenses )

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32
Q

what are the positions and movements of eyelid controlled by ?

A
  • controlled by a series of extra ocular muscles
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33
Q

what are the extra ocular muscles of the eyelids ?

A
  • orbicularis oculi
  • levator palpebrae superioris
  • inferior and superior tarsal muscles ( or muller )
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34
Q

what is the orbicularis oculi ?

A

sphincter muscle of the lids

- close eyelide

35
Q

what is the orbicularis oculi innervated by ?

A

innervated by facial ( VII ) nerve

36
Q

what are the two divisions of the orbicularis oculi ?

A
  • orbital ( outside eyelid ) and palpebral division ( inside eyelid )
  • palpebral division dived
    into pre-septal (orbital septal lies behind )and pre-tarsal ( tarsal plate lies behind this )
37
Q

what is the frontalis muscle ?

A

this is the muscle which extends over forehead and covers the scalp extending to the occipital bone at back of skull
- this muscle is responsible for elevating the eyebrows

38
Q

what is the function of the levator palpebrae superioris ?

A
  • primary responsible for elevating the upper lid in blinking and maintaining an open palpebral aperture
39
Q

what is the levator palpebrae superioris supplied by ?

A

supplied by III nerve ( ocular motor nerve )

40
Q

where does the levator palpebrae superioris arise and terminate ?

A
  • arises from lesser wing of sphenoid - this is at the very back of the orbit - runs above superior rectus muscle - dark of muscle of fibre become white it becomes tendinous as you go forward - the tendon is what insets into the eyelid
  • terminates anteriorly as broad aponeurosis ( sheet of tendon that forms part of the levator palpebrae )
41
Q

what provides the structural support that the two eyelids need ?

A
  • the structural support is provided by the tarsal plate which are attached to the orbital margins through this ligament system
42
Q

what is orbital septum ?

A
  • orbicularis oculi has pre trasal bit of muscle which lies in front tarsal plate
    we also have pre septal part of the muscle
  • orbital septum is sheet of connective tissue which extends from the tarsal plate to orbital rims
43
Q

what is the function of orbital septum ?

A

holds back the orbital content

44
Q

what happens to orbital septum as we get older ?

A

as we get older orbital septum tends to become much less rigid and laxity of old age tends to lead to some of orbital fat being pushed forward against the septum and it bulges forward slightly

45
Q

where does the tarsal muscle lie ?

A

superior tarsal muscle arises from the underside of the levator in upper eyelid and it also attaches to the inferior tarsal plate in the lower eyelid
. insert into the tarsal plate

46
Q

what type of muscle makes up tarsal muscle ?

A

smooth muscle

47
Q

what is tarsal muscle innervated by ?

A

innervated by sympathetic innervation

48
Q

what is function of tarsal muscle ?

A

play a secondary role to the levator in maintaining an open palpebral aperture

49
Q

what are the two characteristics of Horners syndrome ?

A
  • slight drooping of the eyelids ( ptosis ) - lesion along the sympathetic nervous system
  • difference in size of pupil - consequence of lesion to the sympathetic nervous system because muscle that dilates pupil in the iris is inactive due to lesion to its sympathetic supply - thus only muscle working is the one that constricts the pupil
  • another characteristic we don’t see = absence of sweating on the affected side of face
50
Q

what are the six tissue layers that can be resolved in the sagittal section of eyelid ?

A

skin
subcutaneous connective tissue
muscle layer ( orbicularis oculi )
sub muscular connective tissue
tarsal plate ( meibomain gland located within tarsal plate )
palpebral conjunctive - mucous membrane on posterior surface

51
Q

what is the tarsal palate composed of ?

A

composed of dense fibrous connective tissue

52
Q

difference between upper and lower tarsal plate ?

A

both have same length but upper tarsal plate is deeper

53
Q

why are we able to invert an eyelid ?

A

we can invert the eyelid against the upper border of tarsal plate - this involves using cotton bud just above tarsal plate and grabbing hole of eyelashes and flipping eyelids open and applying downward pressure

54
Q

what is the tarsal plate anchored to ?

A

anchored to the orbital margins by the medial and lateral palpebral ligaments

55
Q

what is the function of tarsal plate ?

A

provide support to the eyelids and contain and enclose the meibomian glands

56
Q

what are the glands of the eyelids ?

A
  • meibomian glands - contained within tarsal plate
  • glands of Moll
  • glands of Zeis
57
Q

what are Meibomian gland ?

A
  • large sebaceous glands located in the tarsal plates of the eyelids which produce lipid component of tear film
  • secrete into a central duct that runs down the middle and we have an bout 30 - 40 ducts running in both eyelids
  • longer and more numerous in the upper lid
  • each gland consists of secretory acini which open onto a central duct that discharges its contents onto the lid margin
  • spreads across the team film
58
Q

how do sebaceous gland secrete their secretion ?

A

secrete their secretion to what’s referred to as holocrine mode of secretion - secretory cells accumulates oil within them and the whole of cell and its content are discharged into duct

59
Q

where are the ciliary sebaceous gland located ?

A
  • glands of Moll and Zeis are located in the ciliary zone of the lid
60
Q

what are glands of zeis ?

A
  • glands of zeis are sebaceous glands which open onto lash follicles
  • function is the coat the eyelash with an oily secretion which gives it sticky appearance which helps eyelash with its function of trapping dust and debris
61
Q

what are glands of moll modified into ?

A

glands of moll are modified sweat gland

62
Q

what is the conjunctiva ?

A

the conjunctiva is a transparent mucus membrane which contributes to the immune defence of the ocular surface

63
Q

what is a mucosa ?

A

tissue that contains goblet cells and produces mucus

64
Q

what does the conjunctive produce with respect to the tear film ?

A

produces the mucus component of the tear film

65
Q

what does the transparency of the conjunctiva allow us to see ?

A

the transparency of the conjunctiva affords the view of the blood vessels that are running within the stroma of the conjunctiva

66
Q

where does the conjunctiva extend from ?

A
  • extends from the muco-cutaneous junction at the lid margin , forms a lining to the lids and covers the sclera up to its junction with the cornea
67
Q

what are the 5 anatomic regions of conjunctiva ?

A
  • marginal - bit of conjunctiva that lies adjacent to the eyelid margin
  • tarsal conjunctiva - covers the tarsal plate
  • orbital conjunctiva
  • bulbar conjunctiva - reflected onto the globe
  • limbal conjunctiva - junction with cornea is referred to a limbal conjunctiva
68
Q

what is fornix fold ?

A

the little pocket that’s created as conjunctiva folds back on it’s self

69
Q

what is conjunctival sack ?

A
  • it’s 14-16 mm from the upper eyelid margin through to the upper fornix and slightly shorter 9-11 mm from the lower eyelid margin to the lower fornix
70
Q

what can you see when pulling eyelid downwards away from globe ?

A
  • can see the lower tarsal conjunctiva and you can see the vascular mucosa of the tarsal plate
  • you can see the junction with eyelid and the marginal part extending to the lower fornix
71
Q

what can you see from an inverted upper eyelid ?

A
  • we can see blood vessels seen through the transparency of the conjunctiva
  • can’t see upper fornix as its hidden behind the tarsal plates
72
Q

what can you see in double everting the eyelid ?

A
  • you can see the upper fornix
  • can see sclera
  • can see blood vessel
73
Q

what is the annular zone of conjunctiva around the cornea known as ?

A

known as limbal conjunctiva

74
Q

what does the microscopic structure of conjunctiva show : epithelium ?

A

shows a distinct variation from one zone to next
variation in the thickness and form of the epithelium
variation in goblet cell density located within the conjunctiva

75
Q

what is the distinct anatomical structure in the limbal conjunctiva ?

A
  • palisade of vogt
76
Q

what do goblet cells produce ?

A

produce the mucous component of the tear film

77
Q

what is the characteristic appearance for goblet cells ?

A
  • cytoplasm filled with granules which contains mucous which discharge from the apical surface
  • goblet cell is surrounded by supportive epithelial cells
78
Q

what does the conjunctiva show with respect to goblet cells ?

A
  • the conjunctiva shows a marked regional variation in goblet cell density
  • goblet cell density is much greater medially over the plica semilunaris and caruncle
79
Q

when is goblet cell density much greater ?

A

in upper and lower fornix

80
Q

where is there no goblet cells within the conjunctiva ?

A

there are no goblet cells in the exposed part of the bulbar conjunctiva

81
Q

what are the two distinct layers of the conjunctival stroma ?

A
  • adenoid layer - most superficial layer of stroma
  • this layer contains lots of lymphatics as the conjunctiva has a very effective lymphatic drainage system
  • deep fibrous layer -
82
Q

what does the conjunctiva contain that helps with its immune defense ?

A
  • contains localized accumulations of lymphocytes are found in the conjunctiva; stroma these contain lymphoid follicles (which form mucosal defence system of the conjunctiva) contain predominantly B-cells ( which responsible for antibody mediated immunity ) which form part of the conjunctiva-associated lymphoid tissue
  • increase in size and number in certain anterior eye infections
83
Q

what is the palpebral conjunctiva ?

A

palpebral conjunctiva has a rich blood supply which provides oxygenation of the cornea during eye closure

Neural Biology 1 (58 decks)

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