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Neuro Exam II > Histology of the Eye - SRS > Flashcards

Histology of the Eye - SRS Flashcards

1
Q

The eye is comprised of two compartments divided by the lens, suspensory ligaments and ciliary body into Anterior and Posterior compartments. Describe the contents of these compartments.

A

•Anterior compartment
–Filled with aqueous humor
–Contains anterior and posterior chambers separated by the iris

•Posterior compartment
–Filled with vitreous humor

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2
Q

What are the three tissues of the eye?

A

Corneo-scleral layer (fibrous tunic)

Uveal Layer (Vascular tunic)

Retinal Layer ( Neural Tunic)

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3
Q

What does the corneo-scleral layer make up?

A

Sclera in posterior (5/6) wall of eye

Cornea in anterior 1/6 of the eye (transparent)

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4
Q

What does the Uveal layer make up?

A

Choroid in the posterior (5/6) wall of the eye

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5
Q

What are the accessory structures of the eye? (3)

A

Conjunctiva

Lacrimal Gland

Eyelid

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6
Q

The sclera is the opaque white posterior 5/6 of the eye.

What is it composed of?

Describe the vascularity of the sclera.

A

Composed of collagen and elastin

Nearly avascular

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7
Q

The cornea is the transparent layer in the anterior 1/6 of the eye. Describe its vascularity and innervation levels.

A

Avascular

Highly innervated

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8
Q

What are the five layers of the cornea?

A
  1. Outer epithelium
  2. Bowman’s Membrane
  3. Substantia Propria
  4. Descemet’s Membrane
  5. Corneal Endothelium
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9
Q

What structure is shown here?

What are the indicated layers?

A

Cornea

  1. Outer epithelium
  2. Bowman’s Membrane
  3. Substantia Propria
  4. Descemet’s Membrane
  5. Corneal Endothelium
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10
Q

What cell types make up the outer epithelium of the cornea?

A

Nonkeratinized squamous

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11
Q

What is Bowman’s Membrane?

A

Thin basal lamina of the cornea

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12
Q

Describe the substantia propria of the cornea

A

Dense collagenous tissue with sparse keratinocytes

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13
Q

What is descemet’s membrane?

A

Thick basal lamina of the cornea

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14
Q

What is the role of the corneal endothelium?

A
  1. active transport of fluid out of SP
  2. allowing diffusion of metabolites from aqueous humor
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15
Q

What are the types of refractive error?

A

Myopia

Hyperopia

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16
Q

What is myopia?

A

Nearsightedness

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17
Q

What causes myopia?

A

–Light rays are focused in front of the retina
»Cornea is too curved or
»lens is too powerful for length of globe

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18
Q

What is hyperopia?

A

Farsightedness

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19
Q

What causes hyperopia?

A

–Light rays are focused behind the retina
»Lens and cornea too weak for length of globe

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20
Q

LASIK stands for Laser Assisted In-Situ Keratomieusis. What conditions can be treated with this?

A

Hyperopia and myopia

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21
Q

Describe the procedure for LASIK

A
  1. •A corneal flap is raised using a microkeratome
  2. –About 160 microns thick
  3. •An ultraviolet or “cool laser” is used to ablate a precise amount of the exposed corneal stroma
  4. •The flap is irrigated and replaced
  5. •NO sutures are applied
  6. –The flap remains in place due to the dehydration pump action of the corneal endothelium
  7. •Corneal epithelial cells are replaced by mitotic cells found in the periphery, which migrate into the wound
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22
Q

The uveal layer contains the Choroid, which is the posterior pigmented portion of the vascular layer. What are the histological components of the Choroid?

A

–Loose connective tissue
–Fibroblasts
–Melanocytes

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23
Q

What seperates the choroid from the retina?

A

Bruch’s Membrane

24
Q

What is the component of the choroid next to the retina, which is rich in capillaries?

A

Choriocapillaris

25
Q

The ciliary body is a forward continuation of what layer?

A

The Uveal (vascular) layer

26
Q

The ciliary body is wedge shaped and located between the iris and the vitreous body. What are the histological contents?

A
  1. –Loose connective tissue
  2. –Pigmented epithelium
  3. –Nonpigmented epithelium
  4. –Smooth Muscle
  5. –Zonule Fibers
27
Q

What is the role of the nonpigmented epithelium of the ciliary body?

A

Filter plasma to create aqueous humor

28
Q

Where are the zonule fibers of the ciliary body found?

What do they form?

A
  1. Radiate from the ciliary processes to the lens
  2. Form suspensory ligaments of the lens
29
Q

What are the functions of the ciliary body?

A
  1. Accomodation
  2. Circulation of Aqueous Humor
30
Q

The ciliary muscle is composed of three bundles. What do these open?

Two of these muscles do what?

A

»Opens the canal of Schlemm

»Two stretch the ciliary body
•Occulomotor innervation

31
Q

How does the ciliary body allow focus on nearby objects?

A
  1. The ciliary muscles contract, shortening the ciliary body and releasing tension on the suspensory ligaments.
  2. The lens gets thicker and becomes more convex.
32
Q

Describe the ciliary bodies approach to allowing distant vision

A
  1. Ciliary body is relaxed
  2. Ciliary body with inserted zonula fibers moves away from the lens.
  3. The tension of the zonula fibers increases and the lens flattens
33
Q

What produces aqueous humor?

A

Ciliary processes

34
Q

Describe how aqueous humor flows into and out of the eye.

A

–Enters the posterior chamber, passes through the papillary aperture between the iris and lens and enters the anterior chamber.

–Drains through the trabecular meshwork into the Canal of Schlemm and directly into venous circulation.

35
Q

Where is the corneal-irideal angle?

What forms a scircle here?

A

Between Descemet’s Membrane of the cornea and the anterior surface of the iris.

Canal of Sclem forms a complete circle here.

36
Q

Glaucoma refers to a group of diseases characterized by optic neuropathy resulting in the loss of vision due to?

A

Retinal ganglion cell death

37
Q

What is the number one risk factor for glaucoma?

What is worth noting about this?

A

Increased Intraocular pressure.

This is not however present in all patients, and management of intraocular pressure may not slow the progression.

38
Q

What is the most common form of glaucoma?

A

Open-angle

39
Q

In Open-angle glaucoma the corneal-irideal angle is open. This usually presents with IOP, possiblly due to increased production or decreased outflow. What is characteristic about this condition?

How do you treat?

A

Optic nerve cupping

  • Prostaglandins
  • Beta-blockers
  • Alpha adrenergic agonists
  • Trabeculectomy or trabeculoplasty
40
Q

In angle-closure glaucoma, the corneal -irideal angle is obstructed. What does this lead to?

What is characteristic about this condition?

A

Aqueous outflow is obstructed.

Conjunctival redness

41
Q

The iris is the colored anterior extension of the ciliary body. What does it do?

A

–Controls pupillary aperture
–Separates anterior and posterior chambers

42
Q

The iris has two concentric rings, what are they?

A

•Pupillary zone
–Nearest the pupil and thickest area

•Ciliary zone
–Nearest the ciliary body and widest area

43
Q

What cell types are embedded in the anterior surface of the iris?

A

–Fibroblasts and pigmented melanocytes embedded in extracellular matrix

44
Q

What is eye pigmentation determined by?

A

The number of melanocytes present in the iris.

45
Q

The stroma is a well vascularized portion of the iris. How are the vessels arranged?

46
Q

There are sympathetic and parasympathetic contractile elements to the iris. What are each of these?

A

Sympathetic: Myoepithelial cells making up dilator pupillae muscle

Parasympathetic: Smooth muscle making up sphincter pupillae muscle

47
Q

The posterior surface of the iris is pigmented epithelium. What is it continuous with?

A

Ciliary body

48
Q

The lens is transparent, biconvex, avascular, and supported by zonile fibers making up suspensory ligaments. What are the three components of the lens?

A

Lens capsule

Lens Epithelium

Lens Fibers

49
Q

What is the lens capsule?

A

A thick, transparent basal lamina

50
Q

What cell type is the lens epithelium made of?

A

Single layer of cuboidal cells which are only present on anterior and lateral surface

51
Q

There are ~2000 hexagonal and elongated terminally differentiated cells that form the lens fibers. These contain loose nuclei and organelles during maturation.

What are these filled with?

A

Crystallins

  • Proteins that increase the refractory index of the lens
52
Q

What is the leading cause of blindness in the world?

53
Q

We do not yet know what causes cataracts. What do we know?

A
  • Lens does not shed nonviable cells
  • Lens fibers do not have intracellular mechanism to deal with accumulation of substances
54
Q

What are some risk factors for cataracts?

A

–Advanced age
–Smoking
–Sun exposure
–Alcohol consumption
–Metabolic syndrome
–Diabetes mellitus
–Malnutrition
–Inactivity

55
Q

What is our best guess as to what causes cataracts?

A

Photo/oxidative injury

(unless you have a better idea)

56
Q

What is the treatment for cataracts?

A

Surgical replacement with synthetic intraocular lens.

The lens nucleus is removed, leaving the lens capsule to support the prosthetic.

Neuro Exam II (13 decks)

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