Orbit

Question 1

Bones contributing to the walls of the Orbit:

Answer 1

Superior wall – orbital plate of frontal bone
Lateral wall – greater wing of sphenoid and the orbital plate of zygoma
Inferior wall – orbital plate of maxilla
Medial Wall – frontal process of maxilla, lacrimal bone, orbital plate of ethmoid and the less wing of sphenoid

Question 2

Intrinsic Muscles of the Eye (name and innervation):

Answer 2

Dilator pupillae- sympathetic
Sphincter pupillae- parasympathetic
Ciliary muscle - parasympathetic

Question 3

Extrinsic Muscles of the Eye (name, function and innervation):

Answer 3

4 recti (superior, inferior, medial and lateral) - all innervated by CN 3 apart rom lateral innervated by abducens
2 oblique (inferior CN3, superior CN4)
Eyelid muscles - LPS and orbicularis oculi

Question 4

Ophthalmic branch of CN V –

Branches (name the branch and identify the type of autonomic nerves hitchhiking):

Answer 4

Lacrimal - parasympathetic from the pterygopalatine ganglion

Frontal - supratrochlear and supraorbital

Nasociliary nerve - ciliary branches (sympathetic and the parasympathetic branches), Ethmoidal, infratrochlear

Question 5

Oculomotor Nerve –
This efferent nerve splits into superior and inferior branches, identify the muscles innervated by both branches and describe the autonomic hitchhikers which traverse along them.

Answer 5

• Superior branch:
o Muscles:
 Levator palpebrae superioris
 superior rectus

o Autonomic hitchhiker:
 sympathetic fiber (synapse at superior cervical ganglion C2 and travel to the carotid plexus and ophthalmic artery) innervates Dilator pupillae, blood vessels and the superior tarsal muscles

•	Inferior branch:
o	Muscles:
	 Medial rectus
	 inferior rectus
	 inferior oblique
	
o	Autonomic hitchhikers:
	 Parasympathetic - sphincter pupillae and the ciliary  body


Question 6

Pathway of the Trochlear and Abducent Nerves –

Answer 6

These nerves travel through the cavernous sinus (CN VI travels close to the ICA) and exit the cranium via the superior orbital fissure. CN IV innervates the superior oblique, CN VI innervates the lateral rectus.

Question 7

Arterial supply to the orbit is via the ophthalmic artery which then branches into:

Answer 7

(Some Men Cut Soldiers Like Cheese)

1. supratrochlear
2. muscular branches
3. ciliary
4. supraorbital
5. lacrimal
6. central artery of the retina

Question 8

Venous drainage is via 2 main veins

Answer 8

Venous drainage is via 2 main veins, the superior and inferior ophthalmic veins.

Superior ophthalmic vein - through the superior orbital fissure and into the cavernous sinus
-> all nerves go through here so infection can be very severe

inferior ophthalmic vein - through the inferior orbital fissure and joins the pterygoid plexus

Question 9

What is the consensual response?

Answer 9

Afferent:
retinal gnaglion cells
optic nerve
optic chiasm
optic tract
pre tectal nucleus
edinger westphal nucleus

EFFERENT
edinger westphal nucleus
ciliary ganglion
ciliary nerve
both sphincter pupillae

Question 10

What travels in the superior orbital fissure?

Answer 10

nerve 3,4,V1,6
ophtalmic vein
sympathetic fibres

Question 11

What travels in the inferior orbital fissure?

Answer 11

V2

infraorbital vessels - inferior ophthalmic vein

Question 12

What travels through the optic canal?

Answer 12

the superior ophthalmic artery

optic nerve

Question 13

What is the levator palpabri superioris innervated by?

Answer 13

oculomotor nerve

sympathetic fibres

Question 14

What happens if the oculomotor nerve has a lesion?

Answer 14

1. eye down and out
2. Loss of innervation to the levator palpibrae superioris - ptosis
3. loss of parasympathetic function - mydriasis

Question 15

What is horner syndrome

Answer 15

lesion to upper sympathetic trunk

causes
partial ptosis
Myosis (constricted pupil)
anhydrosis (reduced sweating)

Question 16

Describe the path of the tears in lacrimation

Answer 16

1. lacrimla gland secretes
2. lacrimal sac
3. nasolacrimal duct
4. drain into the inferior meatus