Session 6: Anatomy of the Orbit

Question 1

Which bones make up the roof, floor, medial 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

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

Question 2

Which structures pass through the optic canal?

Answer 2

Optic nerve Ophthalmic artery

Question 3

Which structures pass through the inferior orbital fissure?

Answer 3

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

Infraorbital vessels (infraorbital artery is a branch of maxillary artery which is from external carotid, vein is from union of multiple tributaries)

Question 4

Which structures pass through the superior orbital fissure?

Answer 4

◦Ophthalmic nerve (V1), Oculomotor(III), Trochlear(IV), Abducens(VI)

Superior and inferior opthalmic vein

◦Sympathetic fibres

Question 5

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

Answer 5

Superior Rectus, Inferior Rectus, Lateral Rectus, Medial Rectus

Origin: common tendinous ring at the back of the eye (this is also called annulus of Zinn, annulus= ring)

Insertion: 5 mm behind the corneal margin (onto the sclera)

Question 6

State the innervation of the 6 extrinsic eye muscles?

Answer 6

Lateral Rectus = Abducens (CN 6) (abduct the eye ball)

Superior Oblique = Trochlear (CN 4)

Medial Rectus, Superior Rectus, Inferior Rectus, Inferior Oblique = Oculomotor (CN 3)

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 (pulley) to the postero-lateral superior quadrant of the globe

Question 9

Nerve supply of the oblique muscles (inferior and superior)

Answer 9

◦Inferior oblique (Oculomotor III), superior oblique (Trochlear IV)

Question 10

Which muscle is responsible for elevating the upper eyelid?

Answer 10

Levator palpebrae superioris

palpepabra= eyelid

Question 11

Where is the origin and insertion of this muscle?

Answer 11

Origin: lesser wing of sphenoid

Insertion: superior tarsal plate and skin of the eyelid

tarsal plate= the plate in the eye lid, this is covered by the skin

Question 12

Describe the innervation of this muscle. (levator palpebrae superioris)

Answer 12

◦III (Oculomotor) + sympathetic NS to smooth muscle part of Levatorpalpebrae superioris*

*this muscle has another small smooth muscle attached to it and the smooth muscle is innervated by SNS (smooth muscle is autonomic). However, the rest of Levator palepebrae superioris is innervated by III

sympathetic function is because in fight or flight you would want your eyes wide open to see things

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

Isolated muscle actions of Inferior and superior oblique

Answer 16

inferior oblique: abduct and elevate

Superior Oblique: abduct and depress

Question 17

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

Answer 17

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 18

Which nerve axons make up the optic nerve?

Answer 18

Retinal ganglion cell axons

Retinal ganglion cells is a type of neurons located near the retina,

Question 19

What types of fibres are found within the oculomotor nerve?

Answer 19

Motor fibres to MR, SR, IR, IO and LPS Parasympathetic fibres

The oculomotor nerve has two rami (means branches, in this case, CNIII has superior and inferior branch)

Question 20

What are the branches of the ophthalmic division of the trigeminal nerve (V1)? Which branch is biggest?

Answer 20

Lacrimal - smallest branch (thinnest)

Nasociliary

Frontal – this is the largest (thickest)

Question 21

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

Answer 21

Cavernous sinus

Question 22

Which of the nerves passing through the cavernous sinus, passes through the middle of it rather than passing through along the lateral walls?

Answer 22

Abducens (CN 6)

Question 23

What are the branches of the branches of the ophthalmic division of the trigeminal nerve? (V1)

Answer 23

1. Lacrimal - directly to lacrimal gland
2. Frontal- split into
   - supratrochlear
   - supraorbital
3. Nasociliary
   - branch to ciliary ganglion
   - ethmoidal branch
   - infratrochlear branch

Question 24

What limb of the autonomic nervous system is the ciliary ganglion involved in?

Answer 24

PARASYMPATHETIC

Question 25

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

Answer 25

Fibres entering the ciliary ganglion: preganglionic fibres from the inferior ramus/branch of the oculomotor nerve (Oculomotor splits into superior and inferior branches)

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

Question 26

What do the fibres leaving the ciliary ganglion innervate?

Answer 26

Sphincter pupillae - contraction leads to reduction in pupil size (dilator pupillae in charge of dilation)

Ciliary muscle - controls LENS of eye NOT the size of pupil (contraction leads to NEAR VISION- double check)

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 of orbit

Question 29

Describe the innervation of the lacrimal glands.

Answer 29

Parasympathetic:

Parasympathetic secretomotor fibres of Facial Nerve (CN 7) from the pterygopalatine ganglion via the zygomaticotemporal nerve

Sympa:

from superior cervical ganglion, then the same route as parasympathetic nerve

Sensory:

Lacrimal nerve: branch of opthalmic nerve.

Question 30

Where do the tears initially drain?

Answer 30

Lacrimal Sac, this is the dilated end of the nasolacrimal duct.

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 of eyelid)
• Miosis (excess constriction of eye)
• Anhydrosis (lack of sweating around the eye)
• enopthalmos (shrinking of 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 ?

Answer 35

Strabismus (search up google images)

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