Chapter 15: Anatomy Of The Eye

Question 1

What are the 5 special senses?

Answer 1

1. Vision
2. Taste
3. Smell
4. Hearing
5. Equilibrium

Question 2

How is the eye protected?

Answer 2

By fat cushion and bony orbit

Question 3

What are the 5 accessory structures of the eye?

Answer 3

1. Eyebrows
2. Eyelids
3. Conjunctiva
4. Lacrimal apparatus
5. Extrinsic eye muscles

Question 4

Describe the Eyebrows

Answer 4

Location: over lie supraorbital margins
Functions: shade, prevents perspiration

Question 5

Describe the Eyelids

Answer 5

Location: separate at palpebral (slit), meet in the corners at medial and lateral commissures

Function: blinks reflexively every 3-7 seconds, offers protection from foreign objects and spreads secretion

Eyelashes

Tarsal (Meibomian) glands

Question 6

Tarsal (Meibomian) glands

Answer 6

Modified sebaceous glands produce oily secretion that lubricates lid and eye

Question 7

Describe the Conjuctivia

Answer 7

Transparent mucous membrane that produces a lubricating mucous secretion

Question 8

Conjunctivitis

Answer 8

Inflammation of the conjunctiva resulting in reddened, irritated eyes

Question 9

Pink Eye

Answer 9

Conjunctival infection caused by bacteria or viruses

Question 10

Lacrimal Apparatus

Answer 10

Consists of lacrimal gland and ducts (that drain into nasal cavity)

Process:

1) lacrimal gland secretes lacrimal secretion (tears)
2) tears drain into lacrimal sac and nasolacrimal duct
3) empties into nasal cavity

Question 11

What causes watery eyes when you have a cold (or nasal inflammation) ?

Answer 11

Lacrimal mucosa are swelled which constricts the ducts and prevents tears from draining–> watery eyes

Question 12

Describe Extrinsic Eye Muscles

Answer 12

6 strap like extrinsic eye muscles

• Origin: bony orbit and insert on eyeball
• Function: enables eye to follow moving objects, maintain shape of eyeball, and hold it in orbit

Question 13

What are the 3 layers of the wall of the eye?

Answer 13

1) Fibrous layer
2) Vascular layer
3) Inner layer

• internal cavity filled w/ liquid (humors)

Question 14

Describe the Fibrous Layer

Answer 14

Has 2 regions

• Sclera: protects and shapes eyeball
• Cornea: lets light enter and bends light

• Numerous pain receptors (blinking and tearing reflexes)

Question 15

Describe the Vascular Layer

Answer 15

Also called uvea

Has 3 regions:

1. Choroid
2. Ciliary Body
3. Iris

Question 16

Choroid region

Answer 16

Posterior portion of uvea

• supplies blood to all layers of eye

Question 17

Ciliary Body

Answer 17

Anteriorly, choroid becomes ciliary body

• Consists of smooth muscle bundles, ciliary muscles–> controls shape of lens
• Capillaries of ciliary processes secrete fluid
• Ciliary zonule (from ciliary processes to lens): holds lens in place

Question 18

Iris

Answer 18

Contains the pupil (controls amount of light entering the eye)

Question 19

Describe the Inner Layer (Retina)

Answer 19

Contains:
• Photoreceptor cells (transduce light energy)
• Neurons
• Glial cells

Has 2-layered membrane

• Outer pigmented
• Inner neural layer

Question 20

Outer pigmented layer

Answer 20

Covers ciliary body and iris

• Function:
  1) absorbs light and prevents it from scattering
  2) Phagocytizes photoreceptor cell fragments
  3) Stores vitamin A

Question 21

Inner Neural Layer

Answer 21

3 types of neurons:

1) Photoreceptors
2) Bipolar cells
3) Ganglion cells

Journey of Light:
Signal–> Photoreceptors –> Bipolar cells –> Ganglion cells —(exits eye)—> Optic nerve–> brain

Optic disc (blind spot): optic nerve leaves eye

2 types of photoreceptors:

1) Rods
2) Cones

Question 22

Rods

Answer 22

Dim light, peripheral vision

• more numerous and more sensitive to light
• no color vision

Question 23

Cones

Answer 23

Bright light
- color vision
• Macula lutea
• Fovea centralis

Question 24

Macula lutea

Answer 24

Area at posterior pole lateral to blind spot

- contains mostly cones

Question 25

Fovea centralis

Answer 25

Tiny pit in center of macula lutea that contains all cones, so is region with best visual acuity
- eye movement allows to focus on object so fovea can pick it up

Question 26

Internal chambers and fluids

Answer 26

The lens and ciliary zonule separate eye into 2 segments:

1) Posterior segment
2) Anterior segment

Question 27

Posterior segment

Answer 27

Vitreous humor: transmits lights and contributes to intraocular pressure
- forms in embryo and lasts whole lifetime

Question 28

Anterior segment

Answer 28

Aqueous humor: plasma-like fluid continuously formed by capillaries of ciliary processes

• drained by scleral venous sinus
• Function: supplies nutrients and oxygen mainly to lens and cornea and retina, and remove wastes