L15: Orbit

Question 1

What is the lining of the orbit called? What is this continuous with?

Answer 1

• Periorbita (same as periosteum) - Continuous with dura at optic canal and periosteum outside orbit

Question 2

Bones of orbit?

Answer 2

• Mnemonic: Many Friendly Zebras Enjoy Lazy Picnics - Maxillary, Frontal, Zygomatic, Ethmoid, Lacrimal, Palatine

Question 3

Walls of orbit?

Answer 3

• Medial wall - Lateral wall - Superior wall (aka roof) - Floor - Apex

Question 4

Which wall of the orbit is the thickest and strongest? Thinnest and least strong?

Answer 4

• Thickest/strongest: lateral wall - Thinnest/frail: medial and inferior walls

Question 5

Where is the apex of the orbit located?

Answer 5

• Optic canal in lesser wing of sphenoid bone

Question 6

What is exophthalmos?

Answer 6

• Protrusion of eyeball

Question 7

What are the tarsal plates and glands of the eye?

Answer 7

• Tarsal plates: CT that form skeleton of the lids - Tarsal glands: embedded in tarsal plate, secrete lipid material to lubricate edges of lids

Question 8

What glands are found in the eyelids?

Answer 8

• Ciliary glands: sebaceous glands - Tarsal glands (in tarsal plates): lipid secreting glands to lubricate edges of lids

Question 9

Which muscle elevates the upper eyelid? Innervation?

Answer 9

• Levator palpebrae superioris, by CN III

Question 10

Components of lacrimal apparatus? Location and Function?

Answer 10

• Lacrimal glands/ducts: in lacrimal fossa (superolateral part of orbit), secretes lacrimal fluid - Lacrimal lake: collecting area of tears at medial angle of eye - Lacrimal canaliculi: lateral opening = lacrimal papillae, conveys tears from lacrimal lake to sac - Lacrimal sac: dilated upper end of the nasolacrimal duct, canaliculi open here - Nasolacrimal duct: extends inferiorly into nose, opens at inferior meatus of nasal cavity

Question 11

Innervation of lacrimal gland?

Answer 11

• PSNS fibers carried in greater petrosal nerve of CN VII to pterygopalatine

Question 12

Two conjunctiva of eye?

Answer 12

• Palpebral conjunctiva (covering of eyelid) - Bulbar conjunctiva (covering of eyeball)

Question 13

Extraocular muscles? Innervation?

Answer 13

• SO4 LR6 rest III

Question 14

Action of extraocular muscles?

Answer 14

• Superior rectus: rotate superiorly and medially - Medial rectus: rotate medially - Lateral rectus: rotate laterally - Inferior rectus: rotate inferiorly and medially - Superior oblique: abducts, depresses and rotates laterally - Inferior oblique: abducts, elevates and rotates laterally - Levator palpebrae: elevates superior eyelid

Question 15

Branches of frontal nerve?

Answer 15

• Supraorbital - Supratrochlear

Question 16

Branches of nasociliary nerve?

Answer 16

• Posterior ethmoidal - Anterior ethmoidal - Infratrochlear

Question 17

Nerves that run through superior orbital fissure?

Answer 17

• CN V1 - CN III - CN IV - CN VI

Question 18

Describe autonomic innervation to eye

Answer 18

1.) PSNS - PreG fibers for SM of eye travel with CN III - In orbit, preG fibers branch off CN III and enter into ciliary ganglion, located in orbit along posterolateral side of optic nerve - PostG fibers leave ganglion via short ciliary nerves (branches of CN V1) and enter eyeball, innervating SM of eyeball - Lacrimal gland: supplied by PSNS fibers from greater petrosal (preG fibers) of CN VII. Post G fibers originate from pterygopalatine ganglion and enter orbit via zygomatic branch of maxillary nerve (CN V2) 2.) SNS - PostG sympathetic fibers from sup cervical ganglion enter orbit with wall of blood vessels to eye

Question 19

What blood vessels supply orbit?

Answer 19

• Opthalmic artery (branch off int carotid) enters through optic canal and gives rise to supraorbital, supratrochlear, lacrimal and central artery of retina - Superior and inferior ophthalmic veins drain the eye through the superior orbital fissure and enter cavernous sinus inside the skull

Question 20

What supplies sensory innervation to eyeball?

Answer 20

• Nasociliary

Question 21

What supplies sensory innervation to superior eyelid?

Answer 21

• Frontal, lacrimal

Question 22

What supplies sensory to conjunctiva?

Answer 22

• Lacrimal

Question 23

What bones form the superior wall of orbit?

Answer 23

• Frontal, sphenoid (lesser wing)

Question 24

What bones form the medial wall of orbit?

Answer 24

• Ethmoid, frontal, lacrimal and sphenoid

Question 25

What bones form floor/inferior wall of orbit?

Answer 25

• Maxilla, zygomatic, palatine

Question 26

What bones form lateral wall of orbit

Answer 26

• sphenoid (greater wing), zygomatic

Question 27

PSNS fibers destined for lacrimal gland innervation enter orbit via branches of what CN?

Answer 27

• CN V

Question 28

Do all extraocular muscles attach to sclera of eyeball?

Answer 28

• False. All four recti muscles attach to sclera of eyeball and originate from common tendinous ring, which is a fibrous structure that surrounds optic foramen and part of superior orbital fissure

Question 29

Long and short ciliary nerves are branches from what CN?

Answer 29

• Opthalmic division of CN V

Question 30

Ptosis of the upper eyelid is produced by malfunction of what CN?

Answer 30

• CN III

Question 31

Someone presents to your clinic with ptosis of left eye, inferior lateral rotation of eye and dilated pupil. Explain what the problem is?

Answer 31

• Ptosis is result of loss of function of levator palpebrae superioris - Dilation is seen in SNS, so if SNS is dominating with output causing this, then PSNS innervation to intraocular eye muscles are lost. - Inferior lateral rotation of eye (down and out): MR, IR, SR, IO have lost their function. Lateral rectus and superior oblique still function, causing this movement. - All of these functions are contained within CN III – this is oculomotor palsy.