Muscles of the eye and orbital fascia

Question 1

What are the muscles in the eye?

Answer 1

Dorsal, ventral, lateral and medial rectus
Dorsal oblique
Ventral oblique
Retractor bulbi

Question 2

What do the dorsal, ventral, lateral and medial rectus muscles do?

Answer 2

Rotate eye up - dorsal
Rotate eye down - ventral
Rotate eye medially/lateralyl

Question 3

What nerve innervates the rectus muscles? Which muscle is the exception to this?

Answer 3

CN III occulomotor

Lateral rectus = innervated by abducens CN VI

Question 4

What does the dorsal oblique muscle do? What innervates it?

Answer 4

Rotates dorsal globe medially and ventrally

Trochlear CN IV

Question 5

What dos the ventral oblique muscle do? What innervates it?

Answer 5

Rotates the globe medially and dorsally

Occulomotor CN III

Question 6

What is the action of the retractor bulbi? What is it innervated by?

Answer 6

Retract globe into orbit

Abducens CN VI

Question 7

All eye muscles are innervated by oculomotor nerve (CN III). Which 3 muscles are the exception to this rule?

Answer 7

Lateral rectus = CN VI (abducens)
Dorsal oblique = CN IV (trochlear)
Retractor bulbi = CN VI (abducens)

Question 8

Predators have binocular vision. What does this mean?

Answer 8

Eyes positioned rostrally
Fields of view overlap
Have view of depth

Question 9

Prey have monocular vision. What does this mean?

Answer 9

Eyes positioned laterally
Each eye has own field of view = larger field
Less depth perception

Question 10

Which animals have an incomplete bony orbit? Why?

Answer 10

Cats, dog, pig

Allows wider jaw gape

Question 11

Where is the orbital ligament?

Answer 11

Between the frontal process of the zygomatic bone and the zygomatic process of the frontal bone

Question 12

The bony orbit contains foramina. What do these allow access to?

Answer 12

Opthalmic artery and vein
Orbital vein
Cranial nerves 1-4 and ophthalmic branch of CN V (trigeminal)

Question 13

Which species does not have an orbital ligament? What do they have instead?

Answer 13

Cow

Has bony joint

Question 14

How many layers of orbital fascia are there? What do they do?

Answer 14

3

Line orbit

Question 15

What is the layer of orbital fascia lining the bone? (Innermost)

Answer 15

Periorbita

Question 16

How does the periorbita terminate?

Answer 16

By joining the dura of the optic nerve

Question 17

What does the periorbita do?

Answer 17

Lines bone

Encloses eyeball and associated muscles, nerves and blood vessels

Question 18

Apart from the periorbita, what is the other layer of the orbital fascia?

Answer 18

Fascia bulbi

Question 19

What does the fascia bulbs do?

Answer 19

Surrounds globe and forms 2 layers of orbital fascia

Question 20

How is the fascia bulbi separated from the sclera?

Answer 20

Loose connective tissue

Question 21

What forms the 3rd portion of the orbital fascia?

Answer 21

Fascia bulbi that is continuous with the fascial sheets of extraocular muscles

Question 22

Where do the muscles of the eye originate and insert?

Answer 22

Originate from apex of orbit

Insert caudal to the limbus

Question 23

Which species don’t have a retractor bulbi?

Answer 23

Snake snad brds

Question 24

What is the function of the obicularis oculi?

Answer 24

Sphincter muscle - closes eye and squeezes tears through drainage system

Question 25

What nerve innervates the obicularis oculi?

Answer 25

Facial CN VII

Question 26

What is the muscle that lift the eyelid? What innervates it?

Answer 26

Levator palpebral superioris

Occulomotor

Question 27

What nervous system innervates the smooth muscles of the eyelid?

Answer 27

Sympathetic NS

Question 28

What provides the sensory innervation for the eyelid?

Answer 28

Ophthalmic and maxillary branches of the trigeminal

Question 29

What is the function of the levator anguli occuli? What nerve innervates this?

Answer 29

Smiling muscle

Facial CN VII