Session 6: Anatomy of the Orbit Flashcards
Which bones make up the roof, floor, medial 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
Medial- 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 (infraorbital artery is a branch of maxillary artery which is from external carotid, vein is from union of multiple tributaries)
Which structures pass through the superior orbital fissure?
◦Ophthalmic nerve (V1), Oculomotor(III), Trochlear(IV), Abducens(VI)
Superior and inferior opthalmic vein
◦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 (this is also called annulus of Zinn, annulus= ring)
Insertion: 5 mm behind the corneal margin (onto the sclera)
State the innervation of the 6 extrinsic eye muscles?
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)
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 (pulley) to the postero-lateral superior quadrant of the globe
Nerve supply of the oblique muscles (inferior and superior)
◦Inferior oblique (Oculomotor III), superior oblique (Trochlear IV)
Which muscle is responsible for elevating the upper eyelid?
Levator palpebrae superioris
palpepabra= eyelid
Where is the origin and insertion of this muscle?
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
Describe the innervation of this muscle. (levator palpebrae superioris)
◦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
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
Isolated muscle actions of Inferior and superior oblique
inferior oblique: abduct and elevate
Superior Oblique: abduct and depress
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
Retinal ganglion cells is a type of neurons located near the retina,
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 (means branches, in this case, CNIII has superior and inferior branch)
What are the branches of the ophthalmic division of the trigeminal nerve (V1)? Which branch is biggest?
Lacrimal - smallest branch (thinnest)
Nasociliary
Frontal – this is the largest (thickest)
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, passes through the middle of it rather than passing through along the lateral walls?
Abducens (CN 6)
What are the branches of the branches of the ophthalmic division of the trigeminal nerve? (V1)
- Lacrimal - directly to lacrimal gland
- Frontal- split into
- supratrochlear
- supraorbital - Nasociliary
- branch to ciliary ganglion
- ethmoidal branch
- infratrochlear branch
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 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
What do the fibres leaving the ciliary ganglion innervate?
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)
Name the two ophthalmic veins and state where they drain.
Superior ophthalmic vein = cavernous sinus
Inferior ophthalmic vein = pterygoid plexus
Describe the location of the lacrimal glands.
Anterolateral, superior of orbit
Describe the innervation of the lacrimal glands.
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.
Where do the tears initially drain?
Lacrimal Sac, this is the dilated end of the nasolacrimal duct.
Via which duct do the tears then drain 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 (drooping of eyelid)
- Miosis (excess constriction of eye)
- Anhydrosis (lack of sweating around the eye)
- enopthalmos (shrinking of eye)
Where does the nasolacrimal duct drain?
Inferior nasal meatus
What is the technical term for abnormal alignment of the eyes ?
Strabismus (search up google images)
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
