Orbit, Eye And Lacrimal Apparatus

Question 1

What skeletal bones make up the orbit?

Answer 1

Greater and lesser wing of sphenoid

Frontal

Lacrimal

Ethmoid

Palatine

Maxilla

Zygomatic

Question 2

What are the contents of the orbital openings?

Answer 2

Superior orbital fissure:
- CNIII, IV, V1
- superior ophthalmic vein

Optic canal:
- CNII
- ophthalmic artery

Inferior orbital fissure
- inferior ophthalmic vein

Question 3

Describe the muscles of the eye

Answer 3

Lateral and medial rectus - pull eye to that side

Superior and inferior rectus - help pull eye up or down

Superior oblique - helps pull eye laterally and down

Inferior oblique - helps pull eye superiorly and up

(Oblique muscles only help lateral movements, medial-superior/inferior is done by superior or inferior rectus )

Question 4

What nerve innervates each eye muscle?

Answer 4

Medial rectus - CNIII

Superior rectus - CNIII

Inferior rectus - CNIII

Inferior oblique - CNIII

Levator palpebrae superioris - CNIII

Lateral rectus - CNVI

Superior oblique - CNIV

Question 5

Where is the lacrimal gland? Where are tears secreted?

Answer 5

Upper lateral of the orbit

Secreted into the conjunctival sac and washed across eye via blinking

Question 6

Where are tears drained?

Answer 6

Form a tiny lake at medial of eye in the lateral caruncle and then drain to lacrimal sac

Question 7

How is the lacrimal gland parasympatheticlaly innervated?

Answer 7

CNVII Preganglionic travel in greater petrosal nerve and then pterygoid canal to pterygopalatine ganglion

Fibres then travel via CNV2 zygomatic branch to reach lacrimal gland

Question 8

Describe the cause and symptoms of oculomotor palsy

Answer 8

Injury to oculomotor nerve removes parasympathetic constriction of pupil leaving dilation (mydriasis), and ptosis (drooping eyelid due to loss of levator palpebrae superioris)

also eye is turned down and outwards as medial rectus, inferior rectus injured

Question 9

How is the lens altered for far and near vision?

Answer 9

For far vision:

• ciliary muscles relaxed, so zonular fibres under tension, and lens is stretched so refracts far light

For close:

• ciliary contracted, zonular fibres not under tension and then internal tension causes lens to become thicker and refract light for near vision