extraocular structures

Question 1

structure of upper and lower eyelids

Answer 1

• thin skin (outer surface)
• +/- cilia (eyelashes)
• muscles (for blinking)
• fibrous tarsal plate (confers rigidity)
• glands
• conjunctiva (inner surface)

Question 2

function of eyelids

Answer 2

• globe protection
• tear production, distribution, drainage

Question 3

function of cilia

Answer 3

• protective role
• enhance sensitivity of eyelids

Question 4

function and innervation of levator palpebrae superioris

Answer 4

• function: raise upper eyelid
• innervation: oculomotor (CNIII)

Question 5

function and innervation of Muller’s (smooth muscle)

Answer 5

• function: opens palpebral fissure
• innervation: sympathetic

Question 6

function and innervation of orbiscularis oculi

Answer 6

• function: closes palpebral fissure
• innervation: facial (CN VII)

Question 7

normal efferent pathway of palpebral reflex and menance response:

Answer 7

• CN VII (facial nerve)
• contraction of orbicularis m.

palpebral fissure closure

Question 8

tarsal glands

Answer 8

• also called meibomian glands
• modified sebaceous glands (secrete a mixture of lipids called meibum that form the superficial layer of tear film)
• 20-40 glands per eyelid
• each gland composed of acinar cells connected to a central duct
• orifices at the edge of the eyelid

Question 9

function of the nictitating membrane (3rd eyelid)

Answer 9

• protection
• production of tears (aqueous component)
• distribution of tears on cornea

Question 10

what bones are common in all species of the bony orbit

Answer 10

• zygomatic
• lacrimal
• frontal
• palatine
• sphenoid

Question 11

orbit nerves

Answer 11

• 3 foramens (optic, orbital, round)
• CN II, III, IV, V, VI
• CN VII is NOT an orbital nerve

Question 12

function and innervation of the dorsal rectus

Answer 12

• function: rotate globe upward
• innervation: oculomotor

Question 13

function and innervation of the ventral rectus

Answer 13

• rotates globe downward
• oculomotor

Question 14

function and innervation of the medial rectus

Answer 14

• rotates globe medially
• oculomotor

Question 15

function and innervation of the lateral rectus

Answer 15

• rotates globe laterally
• abducens

Question 16

function and innervation of the dorsal oblique

Answer 16

• rotates dorsal part of globe medially and ventrally
• trochlear

Question 17

function and innervation of the ventral oblique

Answer 17

• rotates ventral part of globe medially and dorsally
• oculomotor

Question 18

function and innervation of the retractor oculi (bulbi)

Answer 18

• retract globe
• abducens

Question 19

soft tissues of orbit

Answer 19

• orbital ligament dorsolaterally in open bony orbits
• primary lacrimal gland under the orbital ligament

Question 20

soft tissues and cavities of orbit

Answer 20

• zygomatic salivary gland (lateral)
• medial pterygoid muscle
• nasal cavity
• frontal sinus

Question 21

orbit vasculature

Answer 21

internal maxillary artery

external carotid - maxillary artery - internal maxillary artery - external opthalmic artery - long and short post-ciliary arteries

Question 22

what is endorbita

Answer 22

• cone-shaped sheet of connective tissue
• contains the retrobulbar soft tissues

Question 23

what are x-rays useful for

Answer 23

assessement of bony orbit and surrounding cavities

Question 24

what is ultrasound useful for

Answer 24

limited visualization of orbital soft tissues

Question 25

CT

Answer 25

• imaging of bone and soft tissue
• transversal and 3D rendition

Question 26

MRI

Answer 26

• less sensitive than CT for orbital bone
• better for globe, optic nerve, exraocular muscles