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Nervous System > Anatomy and Embryology of the Eye > Flashcards

Anatomy and Embryology of the Eye Flashcards

1
Q

where do the optic vesicles grow outwards from?

A

diencephalic part of neural tube towards surface ectoderm

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2
Q

what occurs once the optic vesicles reach the surface ectoderm?

A

cause some of the cells on this surface ectoderm to thicken forming the lens placode

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3
Q

what happens after the lens placode is formed?

A

The lens placode starts to push inwards (invaginate), which causes the optic vesicle too, to form an optic cup

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4
Q

how many layers of the optic cup initially form?

A

2 layered optic cup

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5
Q

what is the fissure that allows blood vessels to pass through inferior optic cup wall?

A

choroid fissure

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6
Q

what ultimately happens to the lens vesicle?

A

looses its connection with the surface ectoderm

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7
Q

what does the surface ectoderm form?

A

eyelids, conjunctiva, corneal epithelium

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8
Q

what does the mesenchyme form?

A

choroid, stroma of cornea, sclera and extraocular muscles

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9
Q

what does the outer layer of the optic cup form?

A

pigment layer of retina and iris

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10
Q

what does the inner layer of the optic cup form?

A

neural layer of retina, ciliary body and inner layer of iris

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11
Q

what forms the lens fibres?

A

epithelium of lens vesicle & later loose their nucleii.

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12
Q

how does retinal detachment usually occur?

A

Tends to happen when fluid gets into potential space between inner 9 layers of retina and 10th outer layer
Can occur following trauma

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13
Q

what occurs if the choroid fissure persists?

A

forms a gap in tissues which develop around it . This gap is called a Coloboma

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14
Q

where can coloboma occur?

A

iris-keyhole pupil
retina
only disc

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15
Q

what are strongest parts of the orbit?

A

orbital rims and lateral and superior walls

rest easily fractured

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16
Q

what can orbital floor fracture lead to?

A

herniation into maxillary sinus

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17
Q

what are common symptoms of an orbital floor fracture?

A

Restricted vertical movement of the eye
Subconjunctival hemorrhage
Swollen lid
Loss of sensation over upper cheek area

18
Q

what eye sign can thyroid disease lead to?

A

Orbital fat hypertrophies leading to the staring appearance

19
Q

describe the epithelium of the cornea

A

stratified squamous non-keratinised.

20
Q

why is the cornea transparent?

A

Histologically – regular arrangement of collagen in stroma
No blood vessels
Endothelium cell layer has a pump that actively keeps the aqueous humor out.

21
Q

give an example of an inflammatory/no inflammatory disease of the cornea

A

Inflammatory – corneal ulcers

Non-inflammatory – dystrophies

22
Q

what do corneal pathologies frequently lead to?

A

opacification of the cornea. This might need to be treated by corneal transplant - Keratoplasty

23
Q

why is the avascularity of the cornea such a benefit to surgeons?

A

a lesser chance of foreign antigens from a corneal graft being recognised by the recipient

24
Q

what is the choroid made up of?

A

fenestrated blood vessels of varying diameter. These supply the outer layers of the retina with blood by diffusion

25
Q

in the retina are the nerve fibres above or below the cones and rods?

A

(except for fovea)
nerve fibres above (9th layer)
layer of rods and cone below (2nd layer)

26
Q

what is the layer that absorbs all the extra light, underneath the layer of rods and cones?

A

Pigment epithelial layer

27
Q

how does the fovea centralis differ from the rest of the retina?

A

packed with cones, so maximum visual acuity

layers have been pushed to side bringing rods & cones up to the surface

28
Q

what is the lens?

A

Transparent, crystalline biconvex structure which is suspended by zonules from the ciliary body. It can change shape (i.e. become less or more convex.)

29
Q

how is the lens transparent?

A

it needs to be avascular

predisposes it to become opaque later in life

30
Q

what is lens opacification called?

A

cataract

31
Q

what is the aqueous humor and what is its role?

A

watery fluid anterior to the lens.It helps maintain intraocular pressure.
constantly circulating fluid that also nourishes the lens and the cornea.

32
Q

what is the vitreous humor and what is its role?

A

transparent gel posterior to the lens.It helps cushion the retina.

33
Q

where is the aqueous humor produced?

A

ciliary body, in the space behind the iris and in front of the lens (the posterior chamber - PC)

34
Q

once inside the anterior chamber where does the aqueous humor go?

A

reaches the angle of the AC where it gets filtered out through a meshwork called the trabecular meshwork

35
Q

at the meshwork where does the aqueous humor go through?

A

Schlemm’s canal

36
Q

what does an obstruction along the pathway of circulation of aqueous humor lead to?

A

damming up of AH-increased intraocular pressure- GLAUCOMA

37
Q

where do the lacrimal gland ducts open into?

A

conjunctival sac

During each blink, eyelids spread tears evenly on the surface of cornea

38
Q

where are the tears drained into?

A

drains into lacrimal sac

Then drains through nasolacrimal duct into the inferior meatus of the nasal cavity.

39
Q

what is the function of tears?

A

keeps cornea moist , prevents drying
Washes away any particulate foreign bodies
Has antibodies and lysozymes -kills microbes
providing smooth surface of cornea for refraction.

40
Q

what nerve leads to secretion of tears?

A

Parasympathetic (VII n)

41
Q

what are the three layers of the tear film?

A

mucinous layer
aqueous layer
oily layer-most superficial

42
Q

what stimulates further blinking?

A

When eyelids are open, aqueous component of tears evaporates, and when oily layer touches mucin layer, tear film breaks up

Nervous System (37 decks)

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