Orbit

Question 1

Recall the bones that contribute significantly to the orbit, recalling which bones make up which wall

Answer 1

Superior: Frontal (orbital plate)

Medial: Maxilla (frontal process), Lacrimal, Ethmoid

Inferior: Maxilla

Lateral: Zygomatic (ant.), Greater wing of sphenoid (post.)

Question 2

What is the role of the extrinsic muscles in the orbit?

Answer 2

Eyeball movement

Upper eyelids

Question 3

What is the role of the intrinsic muscles in the orbit?

Answer 3

Control lens shape and pupil size

Question 4

Describe the location of levator palpebrae superioris

Answer 4

Above superior rectus

Question 5

Recall the functions of LPS

Answer 5

On eyeball: elevate, adduct, medially rotate

On eyelid: elevate when you look up far

Question 6

What is the function of the orbicularis oculi?

Answer 6

Closing the eye

Question 7

Recall the extrinsic muscles of the eye

Answer 7

Superior, inferior, lateral and medial rectus
Superior and inferior oblique
LPS

Question 8

Recall the innervation of the extrinsic eye muscles

Answer 8

Sup + medial rectus, inf oblique. LPS = CNIII
Lateral rectus = CNVI
Sup oblique = CNIV

Question 9

What is the role of the ophthalmic nerve>

Answer 9

SENSORY innervation to inside and around orbit + forehead and nose

Question 10

Recall the arterial supply to the structures of the orbit

Answer 10

Ophthalmic artery (branch of ICA)

Question 11

Recall the venous drainage of the orbit

Answer 11

2 venous channels:

1. Superior ophthalmic vein
2. Inferior ophthalmic vein

Question 12

Recall the nerves and vessels passing through the optic canal

Answer 12

Optic nerve

Ophthalmic artery

Question 13

Recall the nerves and vessels passing through the superior orbital fissure

Answer 13

CNIII,IV,V1,VI,SNS fibres

Ophthalmic veins

Question 14

Recall the nerves and vessels passing through the inferior orbital fissure

Answer 14

CNV2
Inferior ophthalmic vein
Infraorbital vessels

Question 15

What is the clinical significance of the close relationship between the sup. orbital fissure and the cavernous sinus

Answer 15

Sup. ophthalmic VEINS drain into the cavernous sinus, providing a potential route for infection
Can –> cavernous sinus thrombosis

Question 16

Recall the pathway of the pupillary light reflex

Answer 16

Photoreceptors
CNII
Pretectal nucleus
Bilateral edinger-westphal
CNIII
Ciliary ganglia
PNS innervation of sphincter

Question 17

How is pupillary light reflex tested?

Answer 17

Shine light in one eye
Should constrict both pupils
Constriction in tested eye = CNII good
Constriction in other eye = CNIII good

Question 18

Recall the divisions and subdivisions of the ophthalmic nerve (V1)

Answer 18

Frontal and nasociliary
Nasociliary divides into:
Infratrochlear
Ethmoidal
Ciliary (long + short)

Question 19

Recall the stimulatory signal for tear secretion

Answer 19

PNS innervation of lacrimal gland via lacrimal nerve

Question 20

Recall the origins of the lacrimal nerve

Answer 20

1. Pterygo-palatine ganglion
   = PNS branches of V2 (max. div)
2. PNS fibres from facial nerve