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NEURO > Anatomy and physiology of the eye orbit > Flashcards

Anatomy and physiology of the eye orbit Flashcards

1
Q

what are the 5 components that make up the orbit and its contents

A
  1. bony orbit
  2. contents including fat
  3. eyeball
  4. eyelid (and lacrimal ducts)
  5. muscles
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2
Q

what makes up the fibrous coat of the eyeball

A

the sclera and cornea

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3
Q

what makes up the vascular coat of the eyeball

A

the iris, ciliary body and choroid

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4
Q

what makes up the sensory coat of the eyeball

A

the retina (+optic nerve)

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5
Q

what sits between the cornea and the lens in the anterior segment

A

aqueous humour

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6
Q

what sits behind the lens in the anterior segment

A

vitreous humour

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7
Q

what sort of epithelium does the cornea have

A

stratified squamous non-keratinised

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8
Q

what are the different histological layers of the cornea going from the outside to the aqueous humour

A
  1. epithelium
  2. bowmans membrane (basement membrane of corneal epithelium)
  3. stroma - regularly arranged collagen, NO blood vessels
  4. descemets layer
  5. endothelium - single layer
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9
Q

what 3 things allow for the transparency of the cornea to be maintained

A
  1. histologically - regular arrangement of collagen in stroma
  2. NO BLOOD VESSELS
  3. endothelium cell layer has a pump that actively keeps aqueous humour out
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10
Q

why is the cornea believed to be an “immune-privileged” site

A

due to no blood vessels, when performing corneal transplants there is a lesser chance of foreign antigens from a graft being recognised by the recipient - less chance of graft rejection

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11
Q

what comprises the ciliary body of the eye

A 
ciliary muscles (control the shape of the lens)
ciliary epithelium (produce aqueous humour)
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12
Q

what is the trabecular meshwork and where is it located

A

located around the base of the cornea near the ciliary body - drains aqueous humour from the eye via the anterior chamber

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13
Q

where does the trabecular meshwork drain the aqueous humour to

A

schlemms canal - fluid drains into this set of tubes that flow into the blood stream

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14
Q

what is the choroid of the eye

A

vascular layer of the eye made from fenestrated blood vessels of varying diameter - supply outer layers of the retina with blood by diffusion

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15
Q

where is the choroid located

A

lies between retina and sclera

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16
Q

where do the outer layers of the retina get their blood supply from

A

choroid - by diffusion

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17
Q

where do the inner layers of the retina get their blood supply from

A

central retinal artery

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18
Q

what are the 10 layers of the retina (from choroid to vitreous humour)

A
  1. pigment epithelial layer
  2. receptor layer (layer of rods and cones)
  3. outer limiting membrane
  4. outer nuclear layer
  5. outer plexiform layer
  6. inner nuclear layer
  7. inner plexiform layer
  8. ganglion cell layer
  9. nerve fiber layer
  10. inner limiting membrane
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19
Q

what is the macula of the eye

A

area responsible for sharp, detailed, central vision

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20
Q

what is the fovea centralis

A

located in the centre of the macula - contains a very high concentration of cones = MAXIMUM ACUITY

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21
Q

what is the structure of the lens of the eye

A

transparent, crystalline bionvex structure - suspended by zones from the ciliary body - can change shape to become more or less convex

22
Q

why is the lens transparent

A

it is avascular

23
Q

what does vascularity of the lens predispose it to in later life

A

lens opacification - cataract

24
Q

what are the three layers of the tear film

A
  1. mucinous layer (~30%) - overlying corneal epithelium
  2. aqueous layer (~69% - )over mutinous layer
  3. oily layer (<1%) - most superficial layer
25
Q

what are the 4 functions of the tear film

A
  1. keeps cornea moist- prevents drying
  2. washes away particular foreign bodies
  3. antibodies and lysosomes to kill microbes
  4. smooths outer surface of cornea providing smooth surface for refraction
26
Q

what causes secretion of tears into conjunctival sac

A

parasympathetic stimulation of facial (VII) nerve

27
Q

what happens to the tear film during a blink

A

sharp lower border of the upper eyelid evenly distributes tear film over eye

28
Q

how is blinking stimulated

A

when eyelids open aqueous component of tears being to evaporate - oily layer an much layer come close together - when these two layers touch each other the teat film breaks up and stimulates blinking

29
Q

embryologically where do the optic vesicles grow from

A

grow outwards from diencephalic part of neural tube towards ectoderm surface

30
Q

what is the role of the cornea

A

transparent window to allow light rays to enter the body

31
Q

what is the role of the sclera

A

gives attachment to muscles moving the eyeball

32
Q

what is the role of the ciliary body

A

suspends the lens and produces aqueous humour

33
Q

what is the role of the choroid

A

supplies blood to outer layers of retina

34
Q

what is the role of the iris iris

A

controls diameter of pupil and thereby control how much light enters

35
Q

what is the role of the retina

A

contains light sensitive rods and cones which enable us to see

36
Q

what is the aqueous humour

A

watery fluid that helps maintain intraoccular pressure

37
Q

what is the vitreous humour

A

transparent gel that helps cushion the retina

38
Q

what is the role of orbital fat

A

cushions the globe in the orbit

39
Q

what are the components of the eyelids

A

skin on the outside - mucous membrane on the inside (conjunctivae)

eyelashes with sebaceous glands

muscles to elevate and close eyelids

hard plate to keep shape (tarsal plate)

oily secretory glands (to create the tear film)

40
Q

what is the conjunctiva

A

thin vascular membrane that covers the inner surface of the eyelids and loops back over the sclera

DOES NOT cover cornea

41
Q

what does the lacrimal gland do

A

secretes tears that are spread over the surface of the corner with each blink

42
Q

where does the tear film drain

A

lacrimal duct

43
Q

what is the arterial supply of the orbit

A

ophthalmic artery

44
Q

what arteries supply the anterior choroid, ciliary bodies and iris

A

long posterior ciliary arteries

45
Q

what veins drain the orbit

A

superior and inferior ophthalmic veins - drain to the cavernous sinus

46
Q

what happens when the optic vesicles reach the surface ectoderm

A

cells of the surface ectoderm thicken - create the lens placode

47
Q

how is the embryological optic cup formed

A

the lens placode pushes inwards which causes the optic vesicle to do so as well forming a 2 layered optic cup

48
Q

how is the choroid fissure formed

A

as the optic cup is forming, blood vessels that pass through form a fissure in its anterior wall = choroid fissure

49
Q

what does the surface ectoderm go to form

A

eyelids, conjunctivae, corneal epithelium

50
Q

what is the mesenchyme derived from

A

mesoderm and neural crest cells

51
Q

what does the mesenchyme form

A

choroid, storm of cornea, sclera and extraocular muscles

52
Q

what are lens fibres formed from

A

epithelium of the lens vesicle

NEURO (51 decks)

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