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Histology Exam 3 > The Eye - Choroid/Sclera > Flashcards

The Eye - Choroid/Sclera Flashcards

0
Q

Three chambers of the eye

A

Anterior chamber - just behind the cornea (aqueous humor)
Posterior chamber - small wedge shape region posterior to the iris and anterior to the lens (aqueous humor)
Vitreous chamber - large and makes up most of the center of the eye, composed of collagenous vitreous body. Aqueous humor infiltrates the vitreous body

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1
Q

Three layers of the eye

A

Cornea-sclera - mostly dense connective tissue
Uvea - Vascular and loose connective tissue
Retina - the innermost layer made of epithelail and neuro-epithelial cells.

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2
Q

Where is the lens located?

A

Posterior to the anterior chamber and anterior to the vitreous body

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3
Q

Where is the optic nerve?

A

Cranial nerve 2 and emerges from the posterior aspect of the optic globe

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4
Q

Structure of the retina

A

Inner boarder of the wall of the eye abutting the vitreous body
Epithelial like structure with clear lamination (cell layers of nuclei)

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5
Q

Structure of the uvea?

A

Three parts
Anterior - iris and ciliary body
Posterior - choroid

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6
Q

What is the choroid?

A

Part of the uvea and posterior in the eye. Composed of lots of vascular tissue and heavily pigmented.

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7
Q

What is the sclera?

A

Outer layer of the eye composed of densely packed collagen fibers

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8
Q

Function and composition of the sclera?

A

Thick, dense, layer of collagen fibers that provides structural support for the eye and serves as the point of attachment for the extraocular muscles

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9
Q

Tissue makeup of the sclera

A

Dense regular connective tissue

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10
Q

What is the cornea?

A

Part of the sclera (anterior 1/6 of the globe) is made up of such densely and regularly packed collagen fibers that it is transparent

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11
Q

What is the posterior 5/6 of the outer layer of the eye?

A

Sclera, white of the eye

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12
Q

What is the limbus?

A

The region where the cornea and sclera meet

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13
Q

Function of the cornea?

A

Allows light entering from the anterior of the eye

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14
Q

What is the major refractory element in the eye?

A

The cornea

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15
Q

What covers the outer layer of the cornea?

A

Stratified squamous epithelium

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16
Q

What is the Bowman’s membrane?

A

The basement membrane that separates the epithelium from the stroma of the cornea

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17
Q

The majority of the cornea is composed of?

A

Stromal tissue which is made up of regularly arranged collagen fibers. Nuclei of the associated fibroblasts that produced the collagen are visible too.

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18
Q

What is the Descemet’s membrane?

A

The basement membrane on the inner surface of the cornea adjacent to the anterior chamber. Also covered by epithelial tissue called endothelium (large squamous cells)

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19
Q

T or F: The cornea is avascular

A

T (therefore transplants are very successful)

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20
Q

T or F: The cornea is highly innervated

A

T, by free nerve endings making it highly pain sensitive

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21
Q

Describe the fibrous layer of the sclera

A

Composed of elastic, collagen, and fibroblasts to provide structure to the eye.
Much thicker than the choroid or retina.
Poorly vascularized, but serves as the point of attachment of tendons in the extra-ocular muscle

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22
Q

What is the canal of Schlemm?

A

Where the limbus is located and serves to drain the aqueous humor from the eye

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23
Q

Describe the drainage of the aqueous humor

A

Drains from the anterior chamber through trabecular meshworks into the canal of Schlemm and from there to the venous system of the eye

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24
Q

Describe the function of aqueous humor drainage

A

Being continually made by the epithelial cells of the ciliary processes and if excess not drained away can lead to increase in intraocular pressure like in glaucoma

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25
Q

The anterior chamber is just behind the…?

A

The cornea

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26
Q

The posterior chamber is located where?

A

Wedge shaped chamber just behind the iris

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27
Q

The limbus is located where?

A

Cornea/sclera junction in the anterior of the eye

28
Q

The uvea is…?

A

Middle layer of the eye and is highly vascular and pigmented.

29
Q

What is the iris?

A

The anterior portion of the uvea and regulates how much light enters the lense

30
Q

What is the ciliary body?

A

The middle part of the uvea and contains a group of muscles that are used to focus the eye by manipulating the lens

31
Q

What is the choroid?

A

The posterior and majority portion of the uvea and provides the blood supply to the outer layers of the eye

32
Q

What are the two layers of the choroid?

A

Choriocapillary layer

Melanocytes

33
Q

What is the choriocapillary layer?

A

Rich in blood vessels that nourish the outer layers of the retina
Contains both arterioles and venules carrying blood through the uvea and a rich capillary bed in the inner choroid that supplies blood to the retina (outer retina means inner most eye layer)

34
Q

What do the melanocytes do in the choroid?

A

Thick layer in the deep part of the choroid that provides a non-reflective base for the retinal cells to sit on (absorbs light that passes through the retina)

35
Q

Where is the ciliary body located?

A

Between the choroid and the iris and begins at the anterior edge of the photosensitive layers of the retina and ends as the iris begins

36
Q

What composes the ciliary body?

A

Loose connective tissue, blood vessels, and smooth muscle
Consists of:
Ciliary processes - finger like extensions
Ciliary muscle - smooth muscle involved in lens accommodation
Zonule fibers - Attach the ciliary processes to the lens

37
Q

What are ciliary processes?

A

Extend out into the posterior chamber of the eye and are covered by dual layer of epithelial cells

38
Q

What are the pars ciliaris of the retina?

A

Dual layer of epithelial cells that covers the ciliary process

39
Q

What are the two layers of the pars ciliaris of the retina?

A

The superficial non-pigmented ciliary epithelium

The deeper pigmented ciliary epithelium that is the anterior extension of the non-photosensitive region of the retina

40
Q

What produces aqueous humor?

A

The two layers of epithelial cells in the pars ciliaris of the retina on the ciliary processes

41
Q

How is vision focused?

A

By the ciliary body controlling the shape of the lens

42
Q

How is tension maintained in the lens?

A

The zonule fibers extend from the capsule of the lens to the ciliary body

43
Q

T or F: The lens is highly elastic

A

T

44
Q

What happens when the ciliary motor relaxes?

A

The diameter of the lens increases (since the ciliary motor is a sphincter muscle)

45
Q

Upon relaxation of the ciliary muscle and the increase in diameter of the lense…

A

The zonule fibers are under tension which stretches the lens to a flatter state allowing focus on objects at a distance

46
Q

Relaxation of the ciliary muscle allows one to see..?

A

Far objects

47
Q

When the ciliary motor contracts, the lens diameter…?

A

Constricts, pulling the entire ciliary body more anteriorly and reduces tension on the zonule fibers

48
Q

Reduction of tension on the zonule fibers does what?

A

Allows the lens to assume more natural and more round shape allowing focus on objects nearer the eye

49
Q

Relaxation of the ciliary body allows objects to be seen that are…

A

Far

50
Q

Where is the iris?

A

Most anterior extension of the uvea, and outlines the pupil separating the anterior and posterior chambers of the eye

51
Q

What divides the anterior and posterior chambers of the eye?

A

The iris

52
Q

What is the composition of the iris?

A

Loose CT which is highly vascularized and contains melanocytes

53
Q

What are the two cell types of contractile cells in the iris?

A

Radially oriented myoepithelial cells

Circumferentially oriented sphincter smooth muscle

54
Q

What is the function of myoepithelial cells in the iris?

A

Under sympathetic control that dilates the pupil upon contraction.

55
Q

What is the function of the circumferentially oriented smooth muscle fibers in the iris?

A

Parasympathetic control that antagonizes the radial myoepithelial cells to form a sphincter to serve to constrict the pupil diameter

56
Q

What is eye color?

A

The result of light reflecting off the melanin in the stroma of the iris and light reflecting off the dense pigmented epithelial cells on the posterior surface of the iris

57
Q

The posterior surface of the iris is covered in?

A

Pigmented epithelium cells

58
Q

Describe the lens

A

Transparent and biconvex epithelial body comprised of elongated epithelial cells bordered by a lens capsule (analogous to a basement membrane).

59
Q

What is beneath the capsule of the lens?

A

Subcapsular epithelium made up of a single layer of cuboidal epithelium to which the fibers of the lens attach

60
Q

As you move to the equator of the lens, the cuboidal cells appear more?

A

Columnar

61
Q

What are crystallins?

A

Fill fibers with age and change the refractive index of the lens

62
Q

The lens functions to?

A

Accommodate or focus the eye

63
Q

When relaxed, the focal point is? When stretched?

A

Relaxed - distant vision

Stretched - close vision

64
Q

Ciliary muscle relaxes…

A

Zonule fibers are stretched and the lens is flattened to see far

65
Q

Ciliary muscle contracts…

A

Zonule fibers are relaxed, the lens becomes round, see close

66
Q

What is presbyopia?

A

Impairment of vision associated with elasticity of the lens associated with aging. Corrected with glasses
Inability to focus on objects nearer the eye (prevents near field focusing as the lens tends to retain flattened shape)

67
Q

What are cataracts?

A

Caused by clouding of the lens due to accumulation of pigment or overexposure to UV.
Can be fixed by replacing the lens with a prosthetic

Histology Exam 3 (11 decks)

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