Lecture 19 Content

Question 1

What makes up the Fibrous Tunic of the eye?

Answer 1

1. Sclera

2. Cornea

Question 2

describe the sclera?

Answer 2

Dense CT “white of the eye”

• attachment site for extrinsic eye muscles
• elastic/mechanical support for globe

Question 3

Describe the cornea?

Answer 3

• modified sclera (1/6th of globe)
• avascular, several nerve endings
• transparent bulge @ anterior suface
• bulge refracts light before it hits lens
• all nutrients from air

Question 4

What makes up the Vascular Tunic?

Answer 4

1. Choroid
2. ciliary body
3. Iris

Question 5

Describe the Choroid layer?

Answer 5

inner surface of globe (posterior)

• vascular = helps nourish retina
• black pigmentation absorbs stray light

Question 6

Describe the cilary body?

Answer 6

composed of muscles and ligaments

• smooth muscles - radial and circular (sphinter-like) fibers
• suspensory “ligaments” of lens

Question 7

Describe the Iris?

Answer 7

colored portion of the eye

• smooth muscles - radial and circular (sphincter like) fibers
• muscle contractions controls diameter of pupil (hole)
• separates the anterior cavity into ant/post chambers

Question 8

What makes up the anterior cavity?

Answer 8

has 2 chambers anterior to the lens

1. anterior chamber - anterior to the iris
2. posterior chamber - posterior to the iris
3. aqueous humor

Question 9

describe the Aqueous humor?

Answer 9

fills anterior cavity

• produced by the ciliary process
• returned to blood supply via the canal of Schlemm
• helps control intra occulor pressure

Question 10

What makes up the posterior cavity?

Answer 10

posterior to lens (aka vitreous chamber)

• lens to retina
• vitreous humor (gel-like) fills posterior cavity
• assist sclera in maintaining shape of eyeball

Question 11

What is the suspensory ligaments?

Answer 11

barrier between ant/post. cavity

• composed of 3 membrane (fused)
• lens is sandwiched between between layers

Question 12

What is Glucoma?

Answer 12

several different types

• circulation of aqueous humor is blocked
• increased pressure > damage to the optic nerve
• edema in cornea > cloudy/grey-green eye
• offten assoc. w/ high blood pressure (+/- family history

Question 13

The neural tunic is composed of what?

Answer 13

RETINA

• posterior pigmented layer
• anterior pigmented layer

Question 14

What does the Posterior pigmented layer of the Neural tunic do?

Answer 14

• dark pigment absorbs stray light

- supports anterior neural layer

Question 15

What does the anterior “neural” layer do in the neural tunic?

Answer 15

Anterior Neural layer contains 9 layers

• neurons, neuroglia, and blood vessels
• ganglia = integration and preliminary processing
• 130 million photoreceptors in a circular sheet

Question 16

What are the 2 photoreceptors in the eye?

Answer 16

Rods : dim light (light/dark) 125 million per eye

Cones: 6 million per eye - most in the fovea centralis

Question 17

Describe cones in the eye?

Answer 17

• requires “high energy” - bright light
• cone receptors turned to specific wave-lengths
• absense of any one type of cone = color blindness

Question 18

What does the Macula Lutea and the fovea centralis do?

Answer 18

• center of visual axis
• contains high concentration of cones
• spot of greatest resolution (sharpest focus)

Question 19

What is the blind spot?

Answer 19

Point where point where optic nerve exits the globe

• point where blood vessels enter/exit the globe
• located very close to and just medial to the fovea

Question 19

What is the blind spot?

Answer 19

Point where point where optic nerve exits the globe

• point where blood vessels enter/exit the globe
• located very close to and just medial to the fovea

Question 20

Describe the globe of the eye and the retina?

Answer 20

formed as lateral diverticula of the diencephalon

• each diverticulum collapses to form eye cup
• retina this early in neural tube arrangement**
• retina subsequently appears to be installed backwards

Question 20

Describe the globe of the eye and the retina?

Answer 20

formed as lateral diverticula of the diencephalon

• each diverticulum collapses to form eye cup
• retina this early in neural tube arrangement**
• retina subsequently appears to be installed backwards

Question 21

What are some of the clinical implications/ mechanical limitations of the eye?

Answer 21

light receptors (rods and cones) pointing the wrong way
receptors buried behind 9 layers
Blind spot where axons and blood vessels leave globe’
Result of 70 % of the image is lost
ONLY SEE 30%

Question 22

describe the pineal gland?

Answer 22

tied to light reception diurnal behavior patterns

- out-pocketing of the diencephalon

Question 23

Describe the Iris and what CN is it associated with?

Answer 23

CN III - complicated circular and radial muscles (antagonist) - sympathetic simulation > dilation of pupil - parpsympathetic simulation > contraction of pupil = regulates the amount of light that asses to retina

Question 24

describe the ciliary muscles? and what CN is it associated with?

Answer 24

- complicated internal ring of muscles - contraction REDUCES tension of the suspensory ligament - suspensory "ligaments" affect how the lens stretched - shape of lens affects where the eye focuses - CILIARY MUSCLES DO NOT PULL UPON SUSPENSORY LIG.

Question 25

Describe the Lens?

Answer 25

- thick biconvex disc of specialized fibers - orientation of fibers makes the lens transparent - no Blood vessels - suspended from sclera by suspensory ligaments

Question 26

what is accommodation? and what does it do? close and far objects?

Answer 26

ability to focus - requires change in lens shape - little or lens movement close objects? - ciliary muscles contract, slack on suspensory ligaments and lens BULDGE Far objects? - ciliary muscles relax, ligaments tighten and lens FLATTENS

Question 27

what is presbyopia?

Answer 27

- lens becomes stiff with old age - ability to change shape of lens slows - refractive property of lens also change - can't focus on near objects = (far-sighted) - lens is ridged

Question 28

What are cataracts?

Answer 28

(abnormal lens) - combo of structural/bio-mechanical problems - lens becomes cloudy (less light passes to retina) - focusing becomes "patchy" across retina

Question 29

What does the levator palpebrae superioris do? and CN associated with it?

Answer 29

Lift upper eyelid (CN III)

Question 30

What does the obicularis oculi do and CN associated with it?

Answer 30

closes both eye lids (CN VII)

Question 31

What does lateral rectus do and what CN is associated with it?

Answer 31

lateral movement - abducens CN VI

Question 32

What does medial rectus do and what CN is associated with it?

Answer 32

medial movement - oculomotor CN III

Question 33

What does superior rectus do and what CN is associated with it?

Answer 33

superior movement - oculomotor CN III

Question 34

What does inferior rectus do and what CN is associated with it?

Answer 34

Inferior movement - occulomotor - CNIII

Question 35

What does Superior oblique do and what CN is associated with it?

Answer 35

inferior and abduction (laterally) | - Trochlear CN IV

Question 36

What does inferior oblique do and what CN is associated with it?

Answer 36

superior and abduction (laterally) | - oculomotor (CN III)

Question 37

What does the palpebrae do?

Answer 37

upper and lower eyelids

Question 38

What does the Canthi do?

Answer 38

medial and lateral canthus (w/ caruncle)

Question 39

What is the conjunctiva?

Answer 39

``` single layer (skin ) that covers anterior surface of eye - conjunctivitis = pink eye conjunctival inflammations ```

Question 40

What is the lacrimal gland?

Answer 40

superolateral corner of orbit - secretes teas that bathe conjunctiva and cornea - wash, moisten, minimize friction

Question 41

What is the lacrimal apparatus?

Answer 41

- tears are squeezed into medial canthus with each eye blink - tears drain through (lacrimal puncta) into canaliculi - lacrimal sac > nasolarimal duct > nasal cavity

Question 42

what is the Trochlea used for?

Answer 42

sling of CT for superior oblique muscle