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 + zygomatic bone
Which bones make up the medial wall of the orbit?
Lacrimal bone Orbital plate of ethmoid Frontal process of maxilla 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 veins (superior and inferior) Sympathetic fibres
Name the 4 recti muscles and state their origin and insertion.
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)
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 muscle responsible for elevating the eyelid?
Origin: lesser wing of sphenoid Insertion: superior tarsal plate and skin of the eyelid
Describe the innervation of the muscle responsible for elevating the eyelid?
Oculomotor and sympathetic to smooth muscle
Describe the isolated muscle action of the oblique muscles.
Superior oblique = depresses AND abducts Inferior oblique = elevates AND abducts
Describe the isolated muscle action of the superior and inferior recti.
Superior rectus = elevates AND adducts Inferior rectus = depresses AND adducts
Describe how you would test the muscle actions of superior rectus and inferior rectus.
Superior rectus = make the patient abduct their eye and then elevate it
Inferior rectus = make the patient abduct their eye and then depress it
Describe how you would test the muscle actions of superior oblique and inferior oblique.
Superior oblique = make the patient adduct their eye and then depress it Inferior oblique = make the patient adduct their eye and 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 and LPS Parasympathetic fibres The oculomotor nerve has two rami
What are the branches of the ophthalmic division of the trigeminal nerve? Which branch is biggest?
Lacrimal Nasociliary Frontal – this is the largest
What structure do the cranial nerves pass through before reaching the superior orbital fissure?
Cavernous sinus
Which of the nerves passing through the cavernous sinus, passesthrough the middle of it rather than passing through the walls?
Abducens (CN 6)
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 ganglioninvolved 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
