Histo: Eye

Question 1

Most of the eye is derived from neural ectoderm, mesoderm, and neural crest cells. Which part of the eye is derived from surface ectoderm?

Answer 1

Lens

Question 2

What 2 structures does the optic cup give rise to?

Answer 2

1. Ciliary body

2. Iris

Question 3

What 2 structures does the surrounding mesenchyme give rise to.

Answer 3

1. Sclera

2. Choroid

Question 4

Name the 5 layers of the cornea.

Answer 4

1. Non-keratinized Epithelium
2. Bowman’s Membrane (doesn’t regenerate)
3. Corneal Stroma
4. Descemet’s Membrane (can regenerate)
5. Endothelium

Question 5

Name the 3 layers of the sclera.

Answer 5

1. Episcleral Layer
2. Substantia Propria
3. Suprachoroid Lamina

Question 6

Structure that produces aqueous humor.

Answer 6

Epithelial layer of the ciliary body. (simple columnar epithelium)

Question 7

What is the choroid?

Answer 7

Layer of vascular tissue between the sclera and the retina.

• contains 2 layers:
  1. Choriocapillary Layer
  2. Bruch’s Membrane

Question 8

What is the ora serrata?

Answer 8

Poorly defined transition zone in the retina that divides the visual area and the non-visual area.

Question 9

Name the 10 layers of the retina.

Answer 9

1. Retinal Pigmented Layer (closest to choroid)
2. Layer of Rods and Cones
3. Outer Limiting Membrane
4. Outer Nuclear Layer
5. Outer Plexiform Layer
6. Inner Nuclear Layer
7. Inner Plexiform Layer
8. Ganglion Cell Layer
9. Layer of Optic Nerve Fibers
10. Inner Limiting Membrane (closest to vitreous humor)

Question 10

What is Rhodopsin? What kind of nutrient deficiency can impair Rhodopsin formation?

Answer 10

Biological pigment found in rod photoreceptor cells that initiates the signal of light recognition.

Vitamin A deficiency

Question 11

What is Iodopsin?

Answer 11

Biological pigment found in cone photoreceptor cells that initiates the signal of colored vision.

Question 12

Why does the macula allow the sharpest vision?

Answer 12

The ratio of photoreceptor cells to ganglion cells is 1:1 so transfer of information is very efficient.

Other areas of the retina have multiple photoreceptor cells sending information to a single ganglion cell which slows the flow of information.

Question 13

Name the four layers that make up the lens.

Answer 13

1. Outer capsule
2. Subcapsular epithelium (simple cuboidal)
3. Forming Lens Fibers
4. Mature Lens Fibers

(Lens fibers form throughout life but they are never degraded. They form from the outside and are “pushed” toward the center of the lens as we age. The center of adult lenses contain fibers from when they were infants)