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 origin and insertion of the inferior oblique.

Answer 7

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

Question 8

State the origin and insertion of the superior oblique.

Answer 8

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

Question 9

Which muscle is responsible for elevating the eyelid?

Answer 9

Levator palpebrae superioris

Question 10

Where is the origin and insertion of levator palpebrae?

Answer 10

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

Question 11

Describe the innervation of levator palpebrae

Answer 11

Oculomotor and sympathetic to smooth muscle

Question 12

Describe the isolated muscle action of the oblique muscles.

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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 15

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

Answer 15

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 16

Which nerve axons make up the optic nerve?

Answer 16

Retinal ganglion cell axons

Question 17

What types of fibres are found within the oculomotor nerve?

Answer 17

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

Question 18

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

Answer 18

Nasociliary Lacrimal Frontal – this is the largest

Question 19

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

Answer 19

Cavernous sinus

Question 20

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

Answer 20

Abducens (CN 6)

Question 21

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

Answer 21

Lacrimal – no branches Nasociliary  Branch to ciliary ganglion  Ethmoidal  Infratrochlear Frontal  Supratrochlear  Supraorbital

Question 22

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

Answer 22

PARASYMPATHETIC

Question 23

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

Answer 23

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 24

What do the fibres leaving the ciliary ganglion innervate?

Answer 24

Sphincter pupillae Ciliary muscle

Question 25

What are the SIX branches of the ophthalmic artery?

Answer 25

Supratrochlear Supraorbital Lacrimal Ciliary Muscular branches Central artery of the retina

Question 26

Name the two ophthalmic veins and state where they drain.

Answer 26

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

Question 27

Describe the location of the lacrimal glands.

Answer 27

Anterolateral superior orbit

Question 28

Describe the innervation of the lacrimal glands.

Answer 28

Parasympathetic secretomotor fibres of Facial Nerve (CN 7) from the pterygopalatine ganglion via the zygomaticotemporal and, finally, lacrimal nerves

Question 29

Where do the tears initially drain?

Answer 29

Lacrimal Sac

Question 30

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

Answer 30

Nasolacrimal duct – empties into the inferior nasal meatus

Question 31

What nerve does superior oblique muscle follow

Answer 31

trochlea

Question 32

Innervation of inferior rectus muscle

Answer 32

Occulomotor

Question 33

Innervation of supeior rectus muscle

Answer 33

Occulomotor

Question 34

Innervation of medial rectus muscle

Answer 34

Occulomotor

Question 35

Innervation of lateral rectus muscle

Answer 35

Abducens

Question 36

Innervation of superior oblique

Answer 36

Trochlea

Question 37

Innervation of inferior oblique

Answer 37

Occulomotor

Question 38

Nmemonic for branches of opthalmic artery

Answer 38

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Question 39

What are 3 foramina in back of orbit

Answer 39

Infraorbital

Supraorbital

Optic canal