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2. Microanatomy > Eye > Flashcards

Eye Flashcards

1
Q

Eye

A

Photosensitive organ that permits vision and color discrimination
Has a protective reflex (blinks when something moves towards it)

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2
Q

Where is the eye located?

A

Lies in the orbit
Protected by bone laterally and caudally

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3
Q

What are the 3 layers (tunics) of the eyeball?

A
  1. Fibrous (1/5 cornea, 4/5 sclera)
  2. Vascular (choroid, ciliary body, iris)
  3. Nervous (retina- pars optica and para caeca)
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4
Q

What does the Pars caeca include?

A

Blind area:
1. Pars ciliaris (Pigments epith. covering ciliary body)
2. Pars iridica (pigmented epith. covering the iris)

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5
Q

Refractive parts of the eye

A

Cornea
Aqueous humor
Lens
Vitreous Body

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6
Q

Opaque Parts of the Eye

A

Iris
Ciliary body
Choroid

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7
Q

What are the 2 compartments of the eye?

A
  1. Anterior compartment
  2. Posterior compartment
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8
Q

Anterior Compartment

A

Filled with aqueous humor and located between the cornea and lens
Has 2 chambers; anterior and posterior

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9
Q

Anterior and Posterior Chambers

A

Ant: cornea, lens and iris
Post: iris, lens and ciliary bodies
Filled with aqueous humor

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10
Q

Posterior Compartment

A

Between the lens and the retina and filled with vitreous humor

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11
Q

The ________ leaves at the optic disc (fundus)

A

Optic nerve

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12
Q

Aqueous Humor

A

Produced as filtrate of the blood
Like blood plasma but poor in proteins
Provides oxygen and nutrients to intraocular structures

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13
Q

How does aqueous humor move throughout the eye?

A

Formed in ciliary process –> posteror chamber –> anterior chamber via pupil –> spaces of Fontana @ cornea-iris junction –> absorbed into general circulation (Canal of Schelumm)

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14
Q

Function of the cornea-iris junction

A

Drains aqueous humor from anterior chamber

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15
Q

Canal of Schlemm

A

Cornea-scleral junction
Absent in domestic animals

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16
Q

Cornea

A

Forms rostral boundary of anterior chamber, transparent, devoid of BVs

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17
Q

Limbus

A

Cornea-sclera junction
Site of BVs supplying nutrients via diffusion

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18
Q

What are the 5 layers of the cornea?

A
  1. Stratified squamous non-keratin (outer)
  2. Bowman’s membrane (BM)
  3. Substantia propria (stroma, collagen)
  4. Descemet’s membrane
  5. Simple squamous epith. (mitochondria and active pinocytosis)
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19
Q

Significance of substantia propria

A

Thickest layer
Collagen fibers and fibrocytes arranged in right angles

20
Q

What does epithelium of the cornea do?

A

Actively move water out of the stroma

21
Q

Sclera

A

Outermost layer
DRCT
Site of attachment of eye extrinsic muscles

22
Q

Choroid

A

Vascular layer between sclera and retina
Dark layer with melanocytes

23
Q

What are the layers of choroid?

A
  1. Suprachoroid
  2. Vascular
  3. Taptum lucidum
  4. Choriocapillary
  5. Bruch’s membrane
24
Q

How is the Tapetum lucidum is different species?

A

Cellular in dogs and cats
Fibrous in ruminants and horses
Absent in pigs

25
Q

Iris

A

Controls the amount of light entering the eye via smooth muscles:
Sphincter/constrictor: parasym
Radial Dilator: sympathetic

26
Q

Structure of the iris

A

Anterior surface: simple squamous
Core: CT, Bvs and melanocytes
Muscles
Post. surface: bilaminar cuboidal (pars iridica of the retina)

27
Q

Iris muscles are _________ in avian

A

Striated

28
Q

Ciliary processes

A

Irregular projections where zonular fibers attach to the lens
Covered with bilateral cuboidal (non pigmented and pigmented layer)

29
Q

Ciliary muscles

A

Parasympathetic which function in visual accommodation by changing the shape of the lens

30
Q

Lens

A

Lens capsule- collagen IV, simple cuboidal
Lens epithelium- anterior surface
Lens fibers- acellular

31
Q

How are lens fibers formed?

A

By differentiation and elongation of epithelial cells at the equator of the lens
Lose elasticity and plasticity with age

32
Q

Vitreous body

A

“Gel” filled posterior compartment
99% water and 1 % hyaluronic acid (GAGs)

33
Q

Retina

A

2 portions: Pars ceca and Pars optica

34
Q

Pars ceca

A

Non-sensory
Covers ciliary body and iris
Continuation of the pigmented layer of the retina

35
Q

Pars optica

A

Sensory with 10 layers

  1. Outer nuclear layer (nuclei of rods and cones)*
  2. Inner Nuclear layer (bipolar) *
  3. Ganglion layer *
  4. Optical nerve fiber layer (multipolar gang) *
36
Q

How does light pass through the retina?

A

Passes all layers to activate rods and cones –> pigments convert energy in AP –> carried via neuronal connections to the optic nerve

37
Q

Pigment epithelium

A

Squamous to cuboidal
Microvillous processes, melanin
Transfers nutrients from choriocapillary layer to the rods and cones, phagocytosis/ recycling of segments of photoreceptor cells and absorption of light

38
Q

Rods

A

Human eye has 120 million
Rhodopsin pigment
Sensitive to light and suited for dim light vision

39
Q

Cones

A

Human eye has 5 million
Iodopsin pigment
Suited for day light and color discrimination
Macula (fovea) have the highest concentration of cones

40
Q

What clin sigs are for the cornea?

A

Epithelium heal via mitosis
Transplant possible
Dehydration causes corneal opacities
Descemetocele (increased ocular pressure)

41
Q

Glaucoma

A

Increased intraocular pressure
Usually due to blockage in drainage of aqueous humor

42
Q

What clin sigs are for the lens?

A

Lens hardens with age (less elasticity)
Vacuolation
Precipitation of proteins results in cataracts

43
Q

What clin sigs are for the iris/ pupil?

A

Lesion of sympathetic nerve supply –> Horner’s syndrome
Miosis enophthalmos (sunken eyeball)
Ptosis (drooping eyelid)
Mydriasis (from parasym. damage, dilated pupil)

44
Q

Detached Retina

A

Separation occurs between the pigmented layer of the retina and layer of the rods/cones

45
Q

Reason for detached retina?

A

Develops from a bilayer “cup”
Outer layer differentiates into non neural pigmented layer
Inner layer differentiates into nervous layers of the retina
Causing space between cup layers

2. Microanatomy (16 decks)

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