orbit Flashcards
orbit: describe the boundaries of the orbit; describe the location, actions and nerve supply of the intrinsic and extra-ocular muscles (including consequences of nerve injury)
what makes up the roof of the orbit (1 thing)
orbital plate of frontal bone
what makes up the floor of the orbit (1 thing)
orbital plate of maxilla
what makes up the lateral wall of the orbit (2 things)
zygoma, greater wing of sphenoid
what makes up the medial wall of the orbit (4 things)
frontal process of maxilla, lacrimal bone, orbital plate of ethmoid (lamina papyracea), lesser wing of sphenoid
what foramen lies above the orbit in the orbital plate of frontal bone
supraorbital foramen
what foramen lies below the orbit in the frontal process of maxilla
infraorbital foramen
what section of the orbit can be blown out by a squashball injury, and consequence
orbital plate of maxilla, causing eye to drop into cheek cavity (causing double vision)
3 orbital foramina
optic canal, inferior orbital fissure, superior orbital fissure
2 contents of optic canal
optic nerve (CN II) to back of globe, ophthalmic artery
2 contents of inferior orbital fissure
maxillary nerve (CN V2), infraorbital vessels
6 contents of superior orbital fissure
ophthalmic nerve (CN V1), oculomotor nerve (CN III), trochlear nerve (CN IV), abducens nerve (CN VI), ophthalmic vessels, sympathetic fibres
which bone is the optic canal embedded in
lesser wing of sphenoid bone
where does the superior orbital fissure lie
between the lesser and greater wings of sphenoid bone
what 2 bones form the inferior orbital fissure
sphenoid bone and maxilla
where does the maxillary nerve exit through the maxilla bone inferior to the orbit
infraorbital foramen
2 groups of extrinsic eye muscles, and how many of each
4 recti, 2 obliques
what are the 4 recti muscles
inferior, superior, medial, lateral
origin of recti muscles
back of orbit in common tendinous ring
where do recti muscles insert into the eye
sclera, 5mm behind corneal margin
nerve supplying inferior, superior and medial recti
oculomotor (CN III)
nerve supplying lateral rectus
abducens (CN VI)
what are the 2 oblique muscles
inferior, superior
origin of inferior oblique
orbital surface of maxilla
origin of superior oblique
body of sphenoid
where does inferior oblique insert onto eye
posterior/inferior quadrant
where does superior oblique insert onto eye, and via what
poserior/superior lateral quadrant of globe, via trochlea
nerve supplying inferior oblique
oculomotor (CN III)
nerve supplying superior oblique
trochlear (CN IV)
what is the muscle of the upper eyelid
levator papebrae superioris (LPS)
origin of LPS
lesser wing of sphenoid
where does LPS insert
superior tarsal plate and skin of eyelid
nerves supplying LPS
oculomotor (CN III), sympathetic to smooth muscle
what syndrome is associated with loss of sympathetic supply to head
Horner’s syndrome
how does LPS present in Horner’s syndrome
ptosis (drooping upper eyelid)
what is the most superior muscle of the orbit
LPS
what is the second most superior muscle of orbit, below LPS
superior oblique
what direction of eye movement does contraction of superior oblique cause
inferior abduction (down and out)
what is the third most superior muscle of orbit, below LPS and superior oblique
superior rectus
what direction of eye movement does contraction of superior rectus cause
superior (elevation); slight adduction
what direction of eye movement does contraction of inferior oblique cause
superior abduction (up and out)
what direction of eye movement does contraction of inferior rectus cause
inferior (down); slight adduction
what direction of eye movement does contraction of lateral rectus cause (clinical test)
abduction
what direction of eye movement does contraction of medial rectus cause (clinical test)
adduction
how to clinically test between inferior rectus and superior oblique (both depress eye) - H test
get patient to adduct eye first, then depress, to test superior oblique; get patient to abduct eye first, then depress, to test inferior rectus
how to clinically test between superior rectus and inferior oblique (both elevate eye) - H test
get patient to adduct eye first, then elevate, to test inferior oblique; get patient to abduct eye first, then elevate, to test superior rectus
what is intorsion and extorsion
rotational movement by eye muscles
4 nerves of orbit
optic (CN II), oculomotor (CN III), trochlear (CN IV), abducens (CN VI)
what is the optic nerve made out of
ganglion cell axons from retina
number of rami in oculomotor nerve
2
what muscles does oculomotor nerve innervate
medial rectus, superior rectus, inferior rectus, inferior oblique, LPS
what muscle does trochlear nerve innervate
superior oblique
what muscle does abducens nerve innervate
lateral rectus
where does trigeminal ganglion sit
Meckel’s cave, lateral to pituitary gland (this sits below optic chiasm)
3 branches of ophthalmic division of trigeminal nerve (V1)
frontal, lacrimal, nasociliary
what sinus wall do these nerves pass through, before reaching orbit
cavernous sinus
location of cavernous sinus
either side of sphenoid bone
what is on each side of cavernous sinus
folds of dura
what artery passes through cavernous sinus
internal carotid artery to supply anterior part of brain
what nerve doesn’t run in wall of cavernous sinus, and instead runs with internal carotid artery more medially
abducens nerve (V)
4 nerve order in cavernous sinus wall (inferior to superior)
maxillary division of trigeminal nerve (V2), ophthalmic division of trigeminal nerve (VI), trochlear nerve (IV), oculomotor nerve (III)
outcome if cavernous sinus thrombosis or infection
damage to nerves
2 branches of frontal branch of V1 (ophthalmic division of trigeminal nerve), and location where it supplies sensory innervation to skin
supratrochlear, supraorbital (forehead through supraorbital foramen)
3 branches of nasociliary branch of V1 (ophthalmic division of trigeminal nerve)
branch to ciliary ganglion, ethmoidal, infratrochlear
location of ciliary ganglion
just behind globe of eye
ANS division of ciliary ganglion
PSNS
where are preganglionic fibres of ciliary ganglion located
in inferior ramus of oculomotor
where are postganglionic fibres of ciliary ganglion located
in short ciliary nerves
what 2 muscles do ciliary ganglion innervate
sphincter pupillae and ciliary muscle
which artery supplies blood to orbital
ophthalmic artery
what 6 things does ophthalmic artery specifically supply blood to
central artery of retina, muscular, ciliary, lacrimal, supratrochlear, supraorbital
2 ophthalmic veins, and what they drain back into
superior (cavernous sinus; potential route of infection), inferior (pterygoid plexus; not into cranial cavity)
