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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
What allows for far vision?
Relaxed ciliary muscle pulls on the suspensory ligaments, flattening the lens
26
What allows for near vision?
Ciliary muscle contracts, decreasing its overall diameter and tension on the zonule fibers; the lens assumes a more round (convex or clobular) shape
27
What innervates the ciliary muscle?
Parasympathetic nerve fibers (CN III via ciliary ganglion)
28
Within the posterior chamber, the ciliary body contains a number of epithelial folds called ___, which contain a connective tissue core rich in fenestrated capsules.
Ciliary processes
29
What do the ciliary processes do?
Continually produce aqueous humor
30
Aqueous humor is continuously reabsorbed into the ___.
Canal of Schlemm
31
Where is the canal of Schlemm located?
The inner aspect of the corneal margin immediately adjacent to the angle of the anterior chamber
32
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.
Trabeculae
33
Disruption of the transport of aqueous humor can lead to increased intraocular pressure known as ___.
Glaucoma
34
Where does the canal of Schlemm drain?
Channels through the sclera into the episcleral venous system
35
What is the most common cause of blindness?
Glaucoma
36
Increasing intraocular pressure compresses what three things?
Retina, optic nerve, and blood vessels
37
What divides the anterior compartment of the eye into posterior and anterior chambers?
Iris
38
What muscle constricts the pupil?
Constrictor pupillae
39
The constrictor muscle of the pupil consists of a band of ___-oriented smooth muscle fibers in the pupillary aspect of the stroma.
Circumferentially
40
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.
Radially
41
What innervates the constrictor pupillae?
Parasympathetic nervous system
42
What innervates the dilator pupillae?
Sympathetic nervous system
43
The anterior layer of the iris is irregular and consists of a discontinuous layer of ___ and ___.
Fibroblasts; melanocytes
44
___ eyes contain little stromal pigment; ___ eyes have considerable stromal pigment.
Blue; brown
45
What is an elastic, biconvex, transparent body composed almost entirely of living cells?
Lens
46
Embryologically, the lens is derived from ___ epithelium which becomes isolated from the surface during development.
Ectodermal
47
The mature lens is mainly composed of epithelial cells which have become extremely elongated and have lost their ___.
Nuclei
48
___ is a condition where, with age, the eye exhibits a progressively diminished ability to focus on near objects.
Presbyopia
49
What occurs when the optical system is not symmetric about the optical axis?
Astigmatism
50
The vitreous body contains the ___ canal, which extends from the exit of the optic nerve to the posterior surface of the lens.
Hyaloid
51
What are the layers of the retina?
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
Compare rods and cones with respect to sensitivity and specialty.
Rods: high sensitivity, specialized for night vision Cones: lower sensitivity, specialized for daylight vision
53
Which photoreceptor has more photopigments per cell? What does this do?
Rods; captures more light
54
Compare rods and cones with respect to amplification.
Rods: high amplification Cones: less amplification per cell than rods
55
Compare rods and cones with respect to temporal resolution.
Rods: low temporal resolution, slow response, long integration time Cones: high temporal resolution, fast response, short integration time
56
Rods are more sensitive to ___; cones are more sensitive to ___.
Scattered light; direct axial stimulation
57
Rods saturate in ___; cones saturate only in ___.
Daylight; intense light
58
Compare rods and cones with respect to acuity, convergence, and presence in fovea.
Rods: low acuity, high convergent pathways, absent in central fovea region Cones: high acuity, less convergence of retinal pathways, especially in fovea
59
Compare rods and cones with respect to color.
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
True or false - the first action potential occurs in rods and cones.
False - there are no action potentials in rods and cones. The first AP is in the axon of the ganglion cells
61
What are the support cells of the eye that extend between the outer and inner limiting membranes?
Muller cells
62
Tight junctions between the Muller cells form the ___ barrier.
Blood-retinal
63
What happens near the fovea to provide light an unobstructed path to the photoreceptor layer?
Bipolar cells, interneurons, and ganglion cells are pushed laterally; the fovea is also devoid of any large blood vessels
64
What part of the retina has the highest visual acuity?
Fovea
65
In the fovea, the receptors are almost exclusively ___; there are essentially no ___.
Cones; rods
66
Afferent nerve fibers from the retina converge to form the ___.
Optic nerve
67
How does the optic nerve leave the eye?
Through the lamina cribrosa
68
What is the blind spot of the eye?
Optic papilla (disc) - devoid of photoreceptors
69
The blood supply of the eye is derived from the ___ artery via two separate systems - what are these?
Ophthalmic; retinal and uveal systems
70
What supplies the retina?
Central artery of the retina
71
What supplies the uvea?
Branches of the ophthalmic artery which perforate the sclera as the ciliary arteries (long and short)
72
Venous drainage of the retina occurs via the ___, which normally drains directly into the ___.
Central vein of the retina; cavernous sinus

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