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First Semester: Microscopic Anatomy > Lecture 23: Eye > Flashcards

Lecture 23: Eye Flashcards

1
Q

The eyeball (globe) is in a socket called the

A

orbit

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2
Q

Eye is composed of

A
  1. A lens
  2. Outer fibrous tunic
  3. Middle vascular tunic
  4. Inner retinal tunic
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3
Q

Adnexa

A

accessory ocular structures

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4
Q

Adnexa include

A
  • Palpebrae (eyelids)
  • Third eyelid and conjuctiva
  • Lacrimal apparatus
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5
Q

Fibrous tunic includes

A
  • Sclera

- Cornea

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6
Q

Vascular tunic includes

A
  • Iris
  • Ciliary body
  • Choroid
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7
Q

Retina includes

A
  • Pigmented layer

- Neural layer

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8
Q

Sclera

A
  • Posterior portion of eye

- White opaque layer of dense irregular CT

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9
Q

Functions of sclera

A
  • Protects the eye
  • Maintains the shape of eye
  • Provides insertion points for tendons of extraocular muscles
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10
Q

Cornea

A
  • Anterior portion of the eye

- Avascular, transparent convex-concave lens

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11
Q

Cornea is supplied by what nerve

A

opthalmic branch of Cr N V

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12
Q

Cornea water content

A

dehydrated to maintain transparency

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13
Q

Regenerative capacity of cornea

A

High

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14
Q

5 layers of cornea

A
  1. Anterior corneal epithelium
  2. Anterior limiting lamina/subepithelial basement membrane, supporting the lining epithelium
  3. Substantia propria - corneal stroma
  4. Posterior limiting lamina/membrane - Descemet’s membrane, supporting the endothelium
  5. Posterior epithelium of cornea - corneal endothelium
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15
Q

4 factors contributing to corneal transparency

A
  • Avascular
  • Collagen arrangement
  • Proteoglycans between collagen
  • Na+ pumps to transport water out
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16
Q

Limbus of cornea

A
  • Corneoscleral junction

- Where the opaque sclera overlaps the transparent cornea. This area has small blood vessels

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17
Q

Nutrition for the cornea comes from

A

microvasculature of limbus and aqueous humor

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18
Q

The epithelium of the limbus is continuous with

A

the conjunctiva that lines the eyes

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19
Q

Vascular tunic is composed of

A
  1. Iridocorneal angle
  2. Iris
  3. Ciliary body
  4. Choroid
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20
Q

Stroma of the iris

A

-Pigmented loose CT

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21
Q

What determines eye color

A

Iridial melanin present in the stromal cells in the iris

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22
Q

What muscles are in the iris

A

dilator and sphincter pupillae muscles

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23
Q

Posterior epithelium of the iris - equids and ruminants

A

Iridic granules (corpora nigra) are present at the dorsal and ventral pupillary margins

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24
Q

Iridocorneal angle location

A

At the convergence of the corneoscleral junction (limbus), and iris

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25
Q

Iridocorneal angle is composed of

A
  • Pectinate ligament
  • Trabecular meshwork
  • Trabecular (aqueous) veins
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26
Q

Iridocorneal angle function

A

draining point of aqueous humor

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27
Q

Ciliary body

A

Anterior expansion of the choroid at the level of the lens

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28
Q

Ciliary muscle

A
  • Smooth
  • Contracts during accommodation, reduces tension of zonular fibers of the lens
  • Surrounded by loose CT (elastic fibers, vessels, melanocytes)
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29
Q

Ciliary processes are located

A

at the base of the iris

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30
Q

Epithelial surface of ciliary body

A
  • 2 layers of low columnar epithelium
  • Inner pigmented - basement membrane extends to form zonular fibers that suspend the lens
  • Outer nonpigmented - ion transporting forming aqueous humor
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31
Q

Aqueous humor occupies

A

anterior and posterior chambers

32
Q

Purpose of aqueous humor

A
  • Nourishes the cornea (glucose rich)

- Maintains intraocular pressure

33
Q

Aqueous humor is formed by

A

non-pigmented cells of ciliary processes

34
Q

How often does the aqueous humor need to be drained?

A

Constantly

35
Q

Drainage pathway o the aqueous humor

A
  1. Posterior chamber
  2. Through pupil
  3. Anterior chamber
  4. Iridocorneal angle
  5. Past pectinate ligaments
  6. Scleral venous plexus
36
Q

What is the nutritional source of the retina

A

Choroid

37
Q

Anterior choroid

A

Continuous with stroma of ciliary body

38
Q

External choroid

A

Connected to the sclera

39
Q

Internal choroid

A

Connected to retinal pigmented epithelium

40
Q

Dorsal choroid

A

Tapetum lucidum

41
Q

Choroid is _____ vascularized

A

highly

42
Q

Tapetum lucidum

A
  • “Reflective carpet”

- Increases light perception under conditions of poor illumination

43
Q

Does the retinal pigmented epithelium have pigment where the tapetum lucidum is present?

A

Little to none

44
Q

Three parts of the retina

A
  1. Sensory/optical part = contacts the choroid
  2. Non-sensory/ ciliary part = outer nonpigmented epithelium of ciliary body (secretes aqueous humor)
  3. Iridal = posterior pigmented epithelium
45
Q

The retina is nourished by

A

vessels of the choroid and by retinal vessels entering via the optic disk

46
Q

Purpose of sensory/optical retina

A

sends visual images to the brain

47
Q

How many layers does the sensory retina have

A

10

48
Q

Sensory retina is held in place by

A

the vitreous body

49
Q

In the sensory retina, the combined nerve fiber layers converge on optic disc to form

A

the optic nerve

50
Q

General concept of optical retina

A
  1. Light passes through layers of the retina and stimulates photoreceptor cell (rods and cones)
  2. Impulse is passed to bipolar neurons, then to ganglion cells
  3. Axons of ganglion cells form nerve fiber layer. These fibers converge at the optic disk (papilla) and leave the eye as the optic nerve (CN II)

Additional cells with supporting roles include: Amacrine cells, horizontal cells, Muller cells

51
Q

Path of light and visual perception

A
  • Tear film
  • Cornea
  • Aqueous humor
  • Pupil
  • Lens
  • Vitreous humor
  • First 8 layers of retina
  • Stimulating rods or cones
  • Absorbed by retinal epithelium
  • Visual impulse created then passes in reverse order from rods and cones to bipolar cells, ganglion cells, and to optic nerve of the brain
52
Q

Outermost layer of the retina

A

Retinal pigmented epithelium

53
Q

Retinal pigmented epithelium consists of

A

Flat polygonal cells resting on a basement membrane

54
Q

Purpose of retinal pigmented epithelium

A

Transport of nutrients and metabolites to the rods and cones, light absorption, and phagocytosis

55
Q

Photoreceptor layer has neurons called

A

rods and cones

56
Q

Rods and cones have outer and inner segments connected through

A

a cilium

57
Q

Rod structure

A
  • Inner segment of rods is long and thin

- Contain flattened membranous disks containing pigment rhodopsin (vit A)

58
Q

Purpose of rods

A

Responsible for vision in dim light

59
Q

Cone structure

A
  • Inner segment of cones has a broad base

- Disks contain lodopsin

60
Q

Cones purpose

A

Responsible for vision in bright light and color vision

61
Q

Refractive media - vitreous body location

A
  • Occupies space between lens and retina

- 4/5 of eyeball

62
Q

Refractive media - vitreous body structure

A
  • 99% water and rich in hyaluronic acid

- Gel cortex, liquid center

63
Q

Function of vitreous body

A

Aids in maintaining shape, and retinal appostion

64
Q

Refractive media - lens is surrounded by

A

a capsule that is thick anterior surface

65
Q

Anterior epithelium of the lens

A
  • Simple cuboidal cells
  • Apical towards lens fibers
  • At the equator, elongate and differentiate in to lens fibers
66
Q

Lens fibers

A
  • Prism shaped cells, lack nuclei, interdigitate extensively and have gap junctions
  • Differentiation and growth of lens throughout life
67
Q

Refractive media - lens suspended by

A

zonular fibers from the ciliary processes

68
Q

Refractive media - lens loses vascular supply after

A

development

69
Q

The conjunctival epithelium is either

A

psuedostratified columnar or transitional epithelium that becomes stratified squamous near the eyelid margin

70
Q

Third eyelid purpose

A
  • Protects eye, removes foreign bodies

- Gland of 3rd eyelid contributes to 30-50% of aqueous portion of the tear film via multiple very small ductules

71
Q

Third eyelid corresponds to

A

a fold of the conjunctiva formed by hyaline cartilage in ruminants and dogs and elastic cartilage in horses, pigs, and cats

72
Q

What is the third eyelid lined by

A

conjunctiva

73
Q

What may give the surface of the 3rd eyelid a cobblestone appearance?

A

Aggregated lymphatic nodules located under the conjunctiva surface

74
Q

Purpose of the lacrimal gland

A

Tear film moisturizes, lubricates, and protects

75
Q

Lacrimal gland structure

A
  • Tubuloalveolar seromucinous acini composed of secretory cells filled with small granules
  • Myoepithelial cells are present at base
76
Q

Three layers of tear film

A
  1. Oily portion produced by meibomian (tarsal) glands. The oily portion is the superficial layer of a tear film
  2. Aqueous portion consisting of sero-mucous material produced by lacrimal glands, and the glands of the third eyelid
  3. Mucous portion produced by goblet cells in the conjunctiva

First Semester: Microscopic Anatomy (23 decks)

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