Session 6: Anatomy of the Orbit Flashcards
Which bones make up the roof, floor and lateral wall of the orbit?
Roof: orbital plate of frontal bone
Floor: orbital plate of maxillary bone
Lateral wall: greater wing of the sphenoid bone + zygoma
Which bones make up the medial wall of the orbit?
Frontal process of maxilla
Lacrimal bone
Orbital plate of ethmoid
Lesser wing of sphenoid
Which structures pass through the optic canal?
Optic nerve
Ophthalmic artery
Which structures pass through the inferior orbital fissure?
Zygomatic branch of the maxillary division (V2) of trigeminal nerve
Infraorbital vessels
Which structures pass through the superior orbital fissure?
Oculomotor Trochlear Ophthalmic division (V1) of trigeminal Abducens Ophthalmic vessels Sympathetic fibres
Name the 4 recti muscles and state their origin and insertion.
Superior, Inferior, Lateral, Medial
Origin: common tendinous ring (at back of orbit)
Insertion: Sclera, 5 mm behind corneal margin
State the innervation of the 6 extrinsic eye muscles
Lateral Rectus= Abducens (CN 6)
Superior Oblique = Trochlear (CN 4)
Medial Rectus, Superior Rectus, Inferior Rectus,
Inferior Oblique = Oculomotor (CN 3)
State the origin and insertion of the inferior oblique.
Origin: orbital surface of maxilla
Insertion: postero-lateral inferior quadrant of the globe
State the origin and insertion of the superior oblique.
Origin: body of sphenoid
Insertion: via the trochlea to the postero-lateral superior quadrant of the globe
Which muscle is responsible for elevating the eyelid?
Levator palpebrae superioris
Where is the origin and insertion of the levator palpebral superioris?
Origin: lesser wing of sphenoid
Insertion: superior tarsal plate + skin of the eyelid
Describe the innervation of the levator palpebral superioris
Oculomotor + sympathetic to smooth muscle
Describe the isolated muscle action of the oblique muscles.
Superior oblique = depresses + abducts
Inferior oblique = elevates + abducts
Describe the isolated muscle action of the superior and inferior recti.
Superior rectus = elevates + adducts
Inferior rectus = depresses + adducts
Describe how you would test the muscle actions of superior rectus and inferior rectus.
Superior rectus = make patient abduct their eye + then elevate it
Inferior rectus = make patient abduct their eye + then depress it
Describe how you would test the muscle actions of superior oblique and inferior oblique.
Superior oblique = make patient adduct their eye + then depress it
Inferior oblique = make patient adduct their eye + then elevate it
Which nerve axons make up the optic nerve?
Retinal ganglion cell axons
What types of fibres are found within the oculomotor nerve?
Motor fibres to MR, SR, IR, IO + LPS
Parasympathetic fibres
The oculomotor nerve has 2 rami
What are the branches of the ophthalmic division of the trigeminal nerve? Which branch is biggest?
Nasociliary
Lacrimal
Frontal – this is the largest
What structure do the cranial nerves pass through before reaching the superior orbital fissure?
Walls of Cavernous sinus
Which of the nerves passing through the cavernous sinus, passes through the middle of it rather than passing through the walls? What else passes through here?
Abducens (CN 6)
Internal carotid artery also passes through here
What are the branches of the branches of the ophthalmic division of the trigeminal nerve?
Lacrimal (no branches)
Nasociliary:
Branch to ciliary ganglion, Ethmoidal, Infratrochlear
Frontal: Supratrochlear + Supraorbital
What limb of the autonomic nervous system is the ciliary ganglion involved in?
PARASYMPATHETIC
Which fibres enter the ciliary ganglion and which fibres leave the ciliary ganglion?
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
What do the fibres leaving the ciliary ganglion innervate?
Sphincter pupillae
Ciliary muscle
What are the 6 branches of the ophthalmic artery?
Supratrochlear Supraorbital Lacrimal Ciliary Muscular branches Central artery of the retina
Name the 2 ophthalmic veins and state where they drain.
Superior ophthalmic vein: cavernous sinus (potential route of intracranial infection)
Inferior ophthalmic vein: pterygoid plexus
Describe the location of the lacrimal glands.
Anterolateral superior orbit
Describe the innervation of the lacrimal glands.
Parasympathetic secretomotor fibres of Facial Nerve (CN 7) from the pterygopalatine ganglion via the zygomaticotemporal + finally, lacrimal nerves
Where do the tears initially drain?
Lacrimal Sac
Via which duct do the tears drain from the Lacrimal sac and where does this duct empty?
Nasolacrimal duct – empties into the inferior nasal meatus
What is the corneal reflex?
Stimulation of the cornea causes involuntary blinking in both eyes
What is Horner’s syndrome and how does it manifest itself in patients?
It is caused by a disorder of the sympathetic nerves in the brainstem or cervical region
Presents as:
Ptosis
Miosis
Anhydrosis (lack of sweating around the eye)
Where does the nasolacrimal duct drain?
Inferior nasal meatus
What is the technical term for abnormal alignment of the eyes (having a squint)?
Strabismus
What are the different types of strabismus?
Hypotropia – one eye turns down
Hypertropia – one eye turns up
Exotropia – one eye turns out
Esotropia – one eye turns in
Describe the isolated muscle actions of the lateral and medial rectus muscles
Lateral: Abduction
Medial: Adduction
What may infection or thrombosis in cavernous sinus cause?
Direct effects on the cranial nerves passing through
