Session 6: Anatomy of the Orbit

Question 1

Which bones make up the roof, floor and lateral wall of the orbit?

Answer 1

Roof – orbital plate of frontal bone

Floor – orbital plate of maxillary bone

Lateral wall – greater wing of the sphenoid bone + zygomatic bone

Question 2

Which bones make up the medial wall of the orbit?

Answer 2

Lacrimal bone Orbital plate of ethmoid Frontal process of maxilla Lesser wing of sphenoid

Question 3

Which structures pass through the optic canal?

Answer 3

Optic nerve Ophthalmic artery

Question 4

Which structures pass through the inferior orbital fissure?

Answer 4

Zygomatic branch of the maxillary division (V2) of trigeminal nerve Infraorbital vessels

Question 5

Which structures pass through the superior orbital fissure?

Answer 5

Oculomotor Trochlear Ophthalmic division (V1) of trigeminal Abducens Ophthalmic veins (superior and inferior) Sympathetic fibres

Question 6

Name the 4 recti muscles and state their origin and insertion.

Answer 6

Superior Rectus, Inferior Rectus, Lateral Rectus, Medial Rectus Origin: common tendinous ring at the back of the eye Insertion: 5 mm behind the corneal margin (onto the sclera)

Question 7

State the innervation of the 6 extrinsic eye muscles?

Answer 7

Lateral Rectus = Abducens (CN 6) Superior Oblique = Trochlear (CN 4) Medial Rectus, Superior Rectus, Inferior Rectus, Inferior Oblique = Oculomotor (CN 3)

Question 8

State the origin and insertion of the inferior oblique.

Answer 8

Origin: orbital surface of maxilla Insertion: postero-lateral inferior quadrant of the globe

Question 9

State the origin and insertion of the superior oblique.

Answer 9

Origin: body of sphenoid Insertion: via the trochlea to the postero-lateral superior quadrant of the globe

Question 10

Which muscle is responsible for elevating the eyelid?

Answer 10

Levator palpebrae superioris

Question 11

Where is the origin and insertion of the muscle responsible for elevating the eyelid?

Answer 11

Origin: lesser wing of sphenoid Insertion: superior tarsal plate and skin of the eyelid

Question 12

Describe the innervation of the muscle responsible for elevating the eyelid?

Answer 12

Oculomotor and sympathetic to smooth muscle

Question 13

Describe the isolated muscle action of the oblique muscles.

Answer 13

Superior oblique = depresses AND abducts Inferior oblique = elevates AND abducts

Question 14

Describe the isolated muscle action of the superior and inferior recti.

Answer 14

Superior rectus = elevates AND adducts Inferior rectus = depresses AND adducts

Question 15

Describe how you would test the muscle actions of superior rectus and inferior rectus.

Answer 15

Superior rectus = make the patient abduct their eye and then elevate it

Inferior rectus = make the patient abduct their eye and then depress it

Question 16

Describe how you would test the muscle actions of superior oblique and inferior oblique.

Answer 16

Superior oblique = make the patient adduct their eye and then depress it Inferior oblique = make the patient adduct their eye and then elevate it

Question 17

Which nerve axons make up the optic nerve?

Answer 17

Retinal ganglion cell axons

Question 18

What types of fibres are found within the oculomotor nerve?

Answer 18

Motor fibres to MR, SR, IR, IO and LPS Parasympathetic fibres The oculomotor nerve has two rami

Question 19

What are the branches of the ophthalmic division of the trigeminal nerve? Which branch is biggest?

Answer 19

Lacrimal Nasociliary Frontal – this is the largest

Question 20

What structure do the cranial nerves pass through before reaching the superior orbital fissure?

Answer 20

Cavernous sinus

Question 21

Which of the nerves passing through the cavernous sinus, passesthrough the middle of it rather than passing through the walls?

Answer 21

Abducens (CN 6)

Question 22

What are the branches of the branches of the ophthalmic division of the trigeminal nerve?

Answer 22

Lacrimal – no branches

Nasociliary - Branch to ciliary ganglion, Ethmoidal, Infratrochlear

Frontal - Supratrochlear, Supraorbital

Question 23

What limb of the autonomic nervous system is the ciliary ganglioninvolved in?

Answer 23

PARASYMPATHETIC

Question 24

Which fibres enter the ciliary ganglion and which fibres leave the ciliary ganglion?

Answer 24

Fibres entering the ciliary ganglion: preganglionic fibres in the inferior ramus of the oculomotor nerve

Fibres leaving the ciliary ganglion: postganglionic fibres in the short ciliary nerves

Question 25

What do the fibres leaving the ciliary ganglion innervate?

Answer 25

Sphincter pupillae Ciliary muscle

Question 26

What are the SIX branches of the ophthalmic artery?

Answer 26

◦central artery of the retina

◦muscular branches

◦ciliary

◦lacrimal

◦supratrochlear

◦supraorbital

Question 27

Name the two ophthalmic veins and state where they drain.

Answer 27

Superior ophthalmic vein = cavernous sinus Inferior ophthalmic vein = pterygoid plexus

Question 28

Describe the location of the lacrimal glands.

Answer 28

Anterolateral superior orbit

Question 29

Describe the innervation of the lacrimal glands.

Answer 29

parasympathetic secretomotor fibres (from CNVII) from pterygopalatine ganglion via zygomaticotemporal and lacrimal nerves

Question 30

Where do the tears initially drain?

Answer 30

Lacrimal Sac

Question 31

Via which duct do the tears then drain and where does this duct empty?

Answer 31

Nasolacrimal duct – empties into the inferior nasal meatus

Question 32

What is the corneal reflex?

Answer 32

Stimulation of the cornea causes involuntary blinking in both eyes

Question 33

What is Horner’s syndrome and how does it manifest itself in patients?

Answer 33

It is caused by a disorder of the sympathetic nerves in the brainstem or cervical region

Presents as:

Ptosis (drooping upper eyelid)

Miosis (pupil constriction)

Anhydrosis (lack of sweating around the eye)

Question 34

Where does the nasolacrimal duct drain?

Answer 34

Inferior nasal meatus

Question 35

What is the technical term for abnormal alignment of the eyes (having a squint)?

Answer 35

Strabismus

Question 36

What are the different types of strabismus?

Answer 36

Hypotropia – one eye turns down

Hypertropia – one eye turns up

Exotropia – one eye turns out

Esotropia – one eye turns in

Question 37

label this

Answer 37

Question 38

label this

Answer 38

Question 39

label this

Answer 39