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SHB > 10.18.16 Orbit II > Flashcards

10.18.16 Orbit II Flashcards

1
Q

What are the three layers of the eye?

A
  1. Sclera
  2. Choroid
  3. Retina
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2
Q

What surrounds the eye in the orbit?

A

Fat and connective tissue

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3
Q

What does the cornea do?

A

Primary refraction/focusing of light entering the eye

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4
Q

What does the lens do?

A

Secondary focusing of objects onto the retina

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5
Q

What does the iris do?

A

Controls the amount of light falling onto the retina

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6
Q

What are the three chambers of the eye and where are they located?

A
  1. Anterior chamber (between cornea and iris)
  2. Posterior chamber (between iris and lens)
  3. Postremal (vitreous) chamber (behind lens)
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7
Q

Where is the aqueous humor found?

A

Anterior and posterior chambers

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8
Q

Where is the vitreous humor found?

A

Postremal chamber

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9
Q

What type of humor is watery? What type is gelatinous?

A

Watery - aqueous

Gelatinous - vitreous

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10
Q

What is the approximate diameter of the eye?

A

25mm

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11
Q

What are the layers of the eyeball proper?

A
  1. Corneo-scleral layer
  2. Uveal (vascular) layer
  3. Neural layer
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12
Q

What forms a tough, fibro-elastic capsule which supports the eye?

A

Corneo-scleral layer

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13
Q

What is found external to the sclera?

A

Bulbar fascia

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14
Q

What are the layers of the cornea?

A
  1. Stratified squamous epithelium
  2. Bowman’s (basement) membrane
  3. Substantia propria
  4. Decemet’s membrane
  5. Endothelial layer
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15
Q

The episclera is connected by a loose system of collagen fibers to a dense layer of connective tissue called ___, which comes in contact with the conjunctiva at the junction of the cornea and sclera.

A

Tenon’s capsule

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16
Q

The sclera makes up the posterior ___ of the eye.

A

5/6

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17
Q

The cornea makes up the anterior ___ of the eye.

A

1/6

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18
Q

The ___ is the principal refracting medium of the eye and roughly focuses an image onto the retina.

A

Cornea

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19
Q

What is the corneo-scleral junction known as?

A

Limbus

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20
Q

What makes up the bulk of the cornea?

A

Substantia propria

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21
Q

What are the three components of the uveal (vascular) layer?

A
  1. Choroid
  2. Ciliary body
  3. Iris
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22
Q

The ciliary body is lined by a double layer of ___ epithelium.

A

Cuboidal

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23
Q

The ciliary body is attached to the coronal equator of the lens by the ___, which consists of extremely fine collagenous strands which attach to the capsule of the lens.

A

Suspensory ligament (zonule)

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24
Q

What makes up the bulk of the ciliary body?

A

Smooth muscle

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25
Q

What allows for far vision?

A

Relaxed ciliary muscle pulls on the suspensory ligaments, flattening the lens

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26
Q

What allows for near vision?

A

Ciliary muscle contracts, decreasing its overall diameter and tension on the zonule fibers; the lens assumes a more round (convex or clobular) shape

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27
Q

What innervates the ciliary muscle?

A

Parasympathetic nerve fibers (CN III via ciliary ganglion)

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28
Q

Within the posterior chamber, the ciliary body contains a number of epithelial folds called ___, which contain a connective tissue core rich in fenestrated capsules.

A

Ciliary processes

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29
Q

What do the ciliary processes do?

A

Continually produce aqueous humor

30
Q

Aqueous humor is continuously reabsorbed into the ___.

A

Canal of Schlemm

31
Q

Where is the canal of Schlemm located?

A

The inner aspect of the corneal margin immediately adjacent to the angle of the anterior chamber

32
Q

At the angle of the anterior chamber, there is a meshwork of fine connective tissue ___ lined by epithelium. Aqueous humor percolates through the spaces between these before reaching the canal of Schlemm.

A

Trabeculae

33
Q

Disruption of the transport of aqueous humor can lead to increased intraocular pressure known as ___.

A

Glaucoma

34
Q

Where does the canal of Schlemm drain?

A

Channels through the sclera into the episcleral venous system

35
Q

What is the most common cause of blindness?

A

Glaucoma

36
Q

Increasing intraocular pressure compresses what three things?

A

Retina, optic nerve, and blood vessels

37
Q

What divides the anterior compartment of the eye into posterior and anterior chambers?

A

Iris

38
Q

What muscle constricts the pupil?

A

Constrictor pupillae

39
Q

The constrictor muscle of the pupil consists of a band of ___-oriented smooth muscle fibers in the pupillary aspect of the stroma.

A

Circumferentially

40
Q

The deep layer, pigmented in the ciliary body, is transformed in the iris into non-pigmented myoepithelial cells which constitute the ___-oriented dilator pupillae muscle of the iris.

A

Radially

41
Q

What innervates the constrictor pupillae?

A

Parasympathetic nervous system

42
Q

What innervates the dilator pupillae?

A

Sympathetic nervous system

43
Q

The anterior layer of the iris is irregular and consists of a discontinuous layer of ___ and ___.

A

Fibroblasts; melanocytes

44
Q

___ eyes contain little stromal pigment; ___ eyes have considerable stromal pigment.

A

Blue; brown

45
Q

What is an elastic, biconvex, transparent body composed almost entirely of living cells?

A

Lens

46
Q

Embryologically, the lens is derived from ___ epithelium which becomes isolated from the surface during development.

A

Ectodermal

47
Q

The mature lens is mainly composed of epithelial cells which have become extremely elongated and have lost their ___.

A

Nuclei

48
Q

___ is a condition where, with age, the eye exhibits a progressively diminished ability to focus on near objects.

A

Presbyopia

49
Q

What occurs when the optical system is not symmetric about the optical axis?

A

Astigmatism

50
Q

The vitreous body contains the ___ canal, which extends from the exit of the optic nerve to the posterior surface of the lens.

A

Hyaloid

51
Q

What are the layers of the retina?

A
  1. Pigmented epithelial cells resting on the choroid
  2. Photoreceptor layer (rods and cones)
  3. Intermediate layer (interneurons and bipolar cells)
  4. Innermost layer (ganglion cells)
52
Q

Compare rods and cones with respect to sensitivity and specialty.

A

Rods: high sensitivity, specialized for night vision
Cones: lower sensitivity, specialized for daylight vision

53
Q

Which photoreceptor has more photopigments per cell? What does this do?

A

Rods; captures more light

54
Q

Compare rods and cones with respect to amplification.

A

Rods: high amplification
Cones: less amplification per cell than rods

55
Q

Compare rods and cones with respect to temporal resolution.

A

Rods: low temporal resolution, slow response, long integration time
Cones: high temporal resolution, fast response, short integration time

56
Q

Rods are more sensitive to ___; cones are more sensitive to ___.

A

Scattered light; direct axial stimulation

57
Q

Rods saturate in ___; cones saturate only in ___.

A

Daylight; intense light

58
Q

Compare rods and cones with respect to acuity, convergence, and presence in fovea.

A

Rods: low acuity, high convergent pathways, absent in central fovea region
Cones: high acuity, less convergence of retinal pathways, especially in fovea

59
Q

Compare rods and cones with respect to color.

A

Rods: achromatic - only one type of photopigment in rods
Cones: chromatic - three types of cone, each with a pigment sensitive to a different part of the visible spectrum of light

60
Q

True or false - the first action potential occurs in rods and cones.

A

False - there are no action potentials in rods and cones. The first AP is in the axon of the ganglion cells

61
Q

What are the support cells of the eye that extend between the outer and inner limiting membranes?

A

Muller cells

62
Q

Tight junctions between the Muller cells form the ___ barrier.

A

Blood-retinal

63
Q

What happens near the fovea to provide light an unobstructed path to the photoreceptor layer?

A

Bipolar cells, interneurons, and ganglion cells are pushed laterally; the fovea is also devoid of any large blood vessels

64
Q

What part of the retina has the highest visual acuity?

A

Fovea

65
Q

In the fovea, the receptors are almost exclusively ___; there are essentially no ___.

A

Cones; rods

66
Q

Afferent nerve fibers from the retina converge to form the ___.

A

Optic nerve

67
Q

How does the optic nerve leave the eye?

A

Through the lamina cribrosa

68
Q

What is the blind spot of the eye?

A

Optic papilla (disc) - devoid of photoreceptors

69
Q

The blood supply of the eye is derived from the ___ artery via two separate systems - what are these?

A

Ophthalmic; retinal and uveal systems

70
Q

What supplies the retina?

A

Central artery of the retina

71
Q

What supplies the uvea?

A

Branches of the ophthalmic artery which perforate the sclera as the ciliary arteries (long and short)

72
Q

Venous drainage of the retina occurs via the ___, which normally drains directly into the ___.

A

Central vein of the retina; cavernous sinus

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