eyes - anatomy and embryology Flashcards

1
Q

what embryological structure does the eye develop from?

A

optic vesicles of the neural tube

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2
Q

what is the lens placode?

A

structure formed from thickening of the surface endoderm when the optic vesicles reach said endoderm

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3
Q

what happens when the lens placode starts to invaginate?

A

the optic vesicle and lens placode forms an optic cup

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4
Q

how many layers does the optic cup have?

A

2

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5
Q

what is the choroid fissure?

A

fissure in the inferior wall of the optic cup which allows blood vessels to pass through said cup

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6
Q

what is formed when the choroid fissure doesnt disappear as it normally does?

A

a gap in tissues develops around it which is called a coloboma

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7
Q

what is formed from the surface ectoderm?

A

eyelids
conjunctiva
corneal epithelium

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8
Q

what is formed from the mesenchyme?

A

choroid
stroma of cornea
sclera and extraocular muscles

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9
Q

what forms the lens fibres?

A

epithelium of lens vesicle

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10
Q

what can happen if the walls of the bony orbit fracture?

A

contents can herniate into surrounding sinuses

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11
Q

why is orbital fat important?

A

it cushions the globe and is key in supporting the contents

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12
Q

what forms the fibrous coat of the eye?

A

cornea
sclera
aqueous humor

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13
Q

what forms the vascular coat of the eye?

A

iris
ciliary body
choroid

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14
Q

what forms the sensory coat of the eye?

A

retina

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15
Q

what is the cornea?

A

the anterior sixth of the eye which is transparent and is a window to allow light rays to enter the eyeball

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16
Q

what is the sclera?

A

the opaque posterior 5/6 of the eye which gives attachment to the muscles moving the eyeball

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17
Q

what type of epithelium is present in the cornea?

A

stratified squamous non keratinised?

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18
Q

what is bowmans membrane?

A

basement membrane of corneal epithelium

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19
Q

what is the stroma of the cornea?

A

regularly arranged collagen - no blood vessels

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20
Q

what lies between the stroma of the cornea and the endothelium of the cornea?

A

descemets layer

21
Q

how is opacification of the cornea treated?

A

corneal transplant - keratoplasty

22
Q

what are the 2 broad types of cornea pathology?

A

inflammatory - eg corneal ulcer

non inflammatory - dystrophies

23
Q

how is the avascularity of the cornea a benefit during surgery?

A

less chance of grafts being recognised by the recipient so less chance of a rejection

24
Q

what is the purpose of the ciliary body?

A

suspends the lens and produces aqueous humor

25
Q

what is the purpose of the choroid?

A

supplies blood to the outer layers of the retina

26
Q

what is the function of the iris?

A

controls the diameter of the pupil and thereby controls the amount of light rays entering the eyeball

27
Q

what are the 10 layers of the retina?

A
pigment epithelial layer
layer of rods and cones
outer limiting membrane
outer nuclear layer
outer plexiform layer
inner nuclear layer
inner plexiform later
ganglion cell layer
nerve fibre layer
inner limiting membrane
28
Q

what is the clinical term for lens opacification?

A

cataract

29
Q

where is the anterior segment of the eye?

A

in front of the lens

30
Q

where is the posterior segment of the eye?

A

behind the lens

31
Q

where is the anterior chamber of the eye?

A

in front of the iris

32
Q

where is the posterior chamber of the eye?

A

behind the iris

33
Q

what is the aqueous humor?

A

watery fluid anterior to the lens - it helps maintain intraocular pressure

34
Q

what is the vitreous humor?

A

transparent gel posterior to the lens - it helps cushion the retina

35
Q

what is aqueous humor produced by?

A

ciliary body

36
Q

what filters aqueous humor out of the anterior chamber?

A

trabecular meshwork

37
Q

what happens if the pathway of the circulation of the aqueous humor is obstructed?

A

increase in intraocular pressure which leads to glaucoma

38
Q

what are the conjunctiva?

A

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

39
Q

does the conjunctiva cover the cornea?

A

no

40
Q

where is the lacrimal gland situated?

A

in the orbit laterally

41
Q

what innervates the lacrimal gland?

A

facial nerve

42
Q

where do the lacrimal ducts open into?

A

conjunctival sac

43
Q

what happens in regards to lacrimal secretions when we blink?

A

eyelids spread tears evenly on the thin surface of the cornea

44
Q

where do tears drain?

A

through punctae on the medial side of each eyelid and then to the lacrimal sac

45
Q

where is the lacrimal sac situated?

A

over the lacrimal bone

46
Q

where does the lacrimal sac drain to?

A

to the inferior meatus of the nasal cavity through the nasolacriminal duct

47
Q

what are the functions of the tear film?

A
  1. keeps cornea moist
  2. washes away any particulate foreign bodies
  3. has antibodies and lysozymes to kill microbes
  4. smoothes outer surface of the cornea providing smooth surface for refraction
48
Q

what are the 3 layers of the tear film?

A

mucinous layer
aqueous layer
oily layer