Lecture 7 - Orbit and Eye

Question 1

what is the bony orbit?

Answer 1

• bilateral, symetrical cavities containing the eyballs and associated structures

Question 2

What bones/fractions of bones can be found in the bony orbit?

Answer 2

• frontal bone
• sphenoid bone
• ethmoid bone
• lacrimal bone
• palatine bone
• maxilla
• zygomatic bone

Question 3

What fissures/canals are in the bony orbit?

Answer 3

• superior orbital fissure
• inferior orbital fissure
• optic canal

Question 4

What nerves pass through the superior orbital fissure?

Answer 4

• occulomtor nerve (CNIII)
• trochlear nerve (CN IV)
• ophthalmic divison of trigemincal nerve (CN V1)
• abducens nerve (CN VI)

Question 5

What nerve passes through the optic canal

Answer 5

• optic canal (CN II)

Question 6

What are the three layers of the eye? (from deep to superficial)

Answer 6

• inner neural layer (retina)
• middle vascular layer
• outer fibrous layer

Question 7

What structures are within the outer fibrous layer?

Answer 7

• sclera
• cornea
• limbus

Question 8

Cornea

Answer 8

• first refraction of light entering eye
• directs light to lens
• avascular

Question 9

Sclera

Answer 9

• suppoetive outer white layer
• attachment site for extraocular muscles
• covered by mucous membranes (conjunctiva) to lubricate eye
• vascular

Question 10

Limbus

Answer 10

• transition zone between cornea and sclera

Question 11

What structures are within the middle vascular layer?

Answer 11

uvea:
- iris
- cilliary body
- choroid
- lens
- zonular fibers

Question 12

Iris

Answer 12

• contains pupillary dilator and sphincter muscles
• controls pupil size depending on light and NS signals

Question 13

Ciliary body

Answer 13

• produces aqueous humour
• contains ciliary muscles
• helps focus lens using zonular fibers and ciliary muscles

Question 14

lens

Answer 14

• focuses light on retina

Question 15

What are the three muscles in the middle vascular layer?

Answer 15

• intraocular muscles
  -extraocular muscles
• ciliary muscles
• pupillary muscles

Question 16

Intraocular vs extraocular muscles

Answer 16

• intra = within the eye
• extra = outside the eye

Question 17

Ciliary muscles

Answer 17

contracts and relax to change lens so you can see close/far
- when looking far away, muscles contract

Question 18

Pupillary muscles (3)

Answer 18

• iris
• sphincter pupillae
• dilator pupillae

Question 19

Sphincter pupillae

Answer 19

• concentric muscle fibers
• construct pupil when contracted
• parasympathetic NS

Question 20

Dilator pupillae

Answer 20

• muscle fibers run longitudinally towards margins of iris
• enlarges pupils when contracted
• sympathetic NS

Question 21

Pupil size when bright light or PSNS signals

Answer 21

small

Question 22

Pupil size when dim light or SNS signals

Answer 22

large

Question 23

Middle vascular layer - choroid

Answer 23

• nourishes retina
• maintains eye temp and volume

Question 24

Inner neural layer

Answer 24

retina

Question 25

Retina

Answer 25

• macula (fovea in centre)
• optic disc
• ora serrata
• optic nerve

Question 26

macula (fovea in centre)

Answer 26

• highest concentration of photoreceptor cells
• rods and cones

Question 27

optic disc

Answer 27

• where opti nerve exits the eye (optic nerve is made by retinal axons)
• blind spot - no photoreceptors

Question 28

ora serrata

Answer 28

anterior border of retina

Question 29

optic nerve

Answer 29

accumulation of retinal axons

Question 30

Myopia

Answer 30

• near-sightedness
• lens or eyeball is too long
• image is focused in front of fovea

Question 31

Hyperopia

Answer 31

• far-sightedness
• lens or eyeball is too short/flat
• image is focused behind fovea

Question 32

Chambers of the eye

Answer 32

• anterior chamber
• posterior chamber
• vitreous chamber

Question 33

Which chambers are part of the anterior cavity?

Answer 33

• anterior chamber
• posterior chamber

Question 34

Which chambers are part of the posterior cavity?

Answer 34

• vitreous chamber

Question 35

Anterior chamber

Answer 35

• between cornea and iris
• filled with aqueous humor (maintains ocular pressure, replaced every 90 minutes)

Question 36

Posterior chamber

Answer 36

• between iris and lens
• important for production and circulation of aqueous humour

Question 37

Vitreous chamber

Answer 37

• filled with gel-like vitreous humour

Question 38

Vitreous humour

Answer 38

• maintains shape of eye
• nourishes eye
• attached to retina
• makes up about 80% of eye volume
• does not regenerate

Question 39

Extraocular muscles (8)

Answer 39

• trochlea
• superior oblique
• superior rectus
• medial rectus
• lateral rectus
• inferior rectus
• inferior oblique
• levator palebrae superioris

Question 40

Movements of eye: superior oblique

Answer 40

down and out

Question 41

Movements of eye: inferior oblique

Answer 41

up and out

Question 42

What nerve innervates the extraocular muscles? With the exception of two of the muscles with are the…?

Answer 42

• the oculomotor nerve (CN III)
• except for Superior Oblique and Lateral Rectus (SO-LAR)

Question 43

What nerve innervates the superior oblique?

Answer 43

• trochlear nerve (CN IV)
• trochleae = “pulley” = pulls eye

Question 44

What nerve innervates the Lateral Rectus?

Answer 44

abducencs nerve (CN VI)
- abducens abdcuts eye

Question 45

What is the lacrimal apparatus?

Answer 45

system of glands and ducts
- produces and drains lacrimal fluid (tears)

Question 46

What do lacrimal fluid (tears) do?

Answer 46

• lubricate eye surface
• removes debris from eye
• about 1 mL produced each day

Question 47

lacrimal apparatus components/structures

Answer 47

• lacrimal gland
• excretory lacrimal ducts
• superior and inferior puncta
• superior and inferior lacrimal canaliculi
• lacrimal sac
• nasolacrimal duct