Download A) Orbit – describe the bony orbit and fascial sheath that support the

A) Orbit – describe the bony orbit and fascial sheath that support the eyeball within the orbit
a. Paranasal Sinuses – orbit shares walls with 3 sinuses
i. Frontal shares orbital plate of frontal bone
ii. Ethmoid shares thin plate of ethmoid bone
iii. Maxillary shares orbital plate of maxillary bone
b. Fascial Sheath – envelopes eyeball and forms actual socket
i. Check Ligaments
1. Medial – attaches to lacrimal bone, limits adduction
2. Lateral – attaches to zygomatic bone, limits abduction
ii. Suspensory Ligament – forms sling and supports eyeball
iii. Orbital Fat – between fascial sheath and the periorbita
B) Extraocular Muscles – 3 movements => primary, secondary, and tertiary respectively, all are
innervated by Occulomotor nerve (CN III) except superior oblique muscle (trochlear, CN IV) and
lateral rectus muscle (abducent, CN VI), silly remember: SO4 LR6
a. Levator Palpebrae Superioris – lesser wing of sphenoid
to upper eyelid, raises upper lid
b. Recti Muscles – 4 form annulus of Zinn
i. Superior Rectus – elevation, intortion, adduct
ii. Inferior Rectus – depression, extortion, adduct
iii. Medial Rectus - adduct
iv. Lateral Rectus - abduct
c. Superior Oblique – starts at body of sphenoid bone,
ends under superior rectus muscle tendon passes
through a fibrocartilagenous pulley (trochlea) to
form a pulley system. Intort, depress, abduct.
d. Inferior Oblique – starts anterior floor of orbit
passes behind inferior rectus, inserts into eyeball.
Extort, elevate, abduct.
C) Eyeball – coats of eyeball and their contents
a. Coats
i. Fibrous – corneosclear junction is the limbus
1. Sclera
a. Optic nerve enters at lamina cribrosa
b. Opthalmic nerve/vein/argery pierce it
c. Extraocular muscles attach to it
2. Cornea – avascular, but sensitive to touch
ii. Uvea
1. Choroid – highly vascular
2. Ciliary Body – anterior continuation of choroid
a. Ciliary Muscle – smooth muscle attached to ciliary processes,
distal end becomes zonule that attaches around lens,
innervated by ciliary ganglion
i. Relaxed for viewing in the distance, tension from ciliary
processes keeps lens thin
ii. Contracts for distal viewing, ralxes ciliary processes and
zonules, lens becomes more rounded in shape
3. Iris – thin diaphragm with aperture called pupil, periphery attahces to
anterior surface of ciliary body
a. Sphincter Pupillae Muscle – constricts pupil, responds to
increased light coming to eye and focusing on near objects, PS
short ciliary nerves from ciliary ganglion
b. Dilator Pupillae Muscle – dilates pupil, due to decreased light
and excessive sympathetic stimulation such as that in fright,
sympathetic fibers that come with long ciliary nerves travelling
with nasociliary nerve
4. Retina
a. Optic Disc
i. Optic nerve
ii. Central retinal artery
b. Optic Chiasm – nerves from medial half cross
midline, lateral half pass on same side
b. Interior – lens separates into anterior/posterior
i. Anterior – filled with aqueous humor which is made by ciliary
body, collected in anterior chamber of limbus at the trabecular meshwork,
merge to form sclera venous sinuses (canals of Schlemm), goes into veins in
sclera
ii. Posterior – filled with vitreous body
D) Neurovascular – for orbit and eyeball, plus relationship to cavernous sinus
a. Cavernous Sinus – dural venous sinus, space in dura mater
here the layers have separated and venous blood fills the space
i. Internal carotid runs through center, surrounded by
sympathetic
ii. Abducent nerve (CN VI) courses with internal carotid, goes to superior orbital
fissure
iii. Fibrous outer wall contains four cranial nerves – all enter orbit except CNV2
1. Oculomotor (CN III)
2. Trochlear (CNIV)
3. Opthalmic (CN V1)
4. Maxillary (CN V2) –traverse foramen rotundum -> pterygopalatine fossa
b. Opthalmic Artery – branches from internal carotid
i. Central artery of retina – with optic nerve
through disc
ii. Ciliary arteries – into sclera to supply uvea
iii. Lacrimal artery – to lacrimal gland
iv. Supraorbital artery
v. Supratrochlear artery
vi. Anterior ethmoid artery
vii. Posterior ethmoid artery
c. Opthalmic Veins
i. Supratrochlear + Supraorbital veins ->
Superior ophthalmic vein ->
superior orbital fissure ->
internal jugular vein
ii. Veins on floor of orbit->
Inferior ophthalmic vein –[
[-> superior orbital fissure
[-> inferior orbital fissure -> pterygoid venous plexus
d. Somatic
i. Occulomotor Nerve (CNIII) – somatic motor and
parasympathetic
1. Superior division: levator palpebrae superioris, superior rectus
2. Inferior division: medial rectus, inferior rectus, inferior oblique
ii. Trochlear Nerve (CN IV) – somatic motor to superior oblique muscle
iii. Opthalmic Nerve (CN V1) – somatic sensory to cornea and sclera
1. Lacrimal – somatic sensory to lacrimal gland and conjunctiva and skin,
travels in lateral part of orbit
2. Frontal – most superior structure, two branches to skin, upper eyelid,
and forehead, supratrochlear and superorbital nerves, also innervates
frontal sinus
3. Nasociliary – 5 branches
a. Ciliary ganglion branches – through ciliary ganglion
b. Long ciliary nerves – enter eyeball with sympathetic
fibers for dilator pupil
c. Posterior ethmoid nerve – mucosa of posterior
ethmoid and sphenoid sinuses
d. Anterior ethmoid nerve – mucosa of anterior and
superior nasal cavity, external nasal nerve goes
to tip of nose
e. Infratrochlear nerve – skin on medial eyelid
iv. Abducent Nerve (CN VI) – see internal carotid in cavernous sinus
e. Parasympathetics
i. Ciliary Ganglion – parasympathetic fibers from occulomotor nerve,
parasympathetic preganglionic fibers synapse on parasympathetic
postganglionic neuron cell bodies in ciliary ganglion, fibers exiting become part
of short ciliary nerves to eyeball
1. Roots
a. Occulomotor
b. Internal carotid
c. Nasociliary nerve
2. Branches – short ciliary nerves for
a. parasympathetic postganglionic fibers to ciliary muscle and
sphincter pupillae muscle
b. sympathetic postganglionic to fibers in blood vessels of choroid
c. somatic sensory to cornea
ii. Sympathetics – along internal carotid, but not just short ciliary branches, but
long ciliary too
1. Innervate dilator papillae vis long fibers
2. Muller’s muscle in upper eyelid
3. Blood vessels in uvea via short fibers
E) Eyelids – protect eyeball from injury, excessive light, and drying out
a. Orbital Septum – fibrous framework core of eyelid, thickens at center to form
tarsal plates, opening between two eyelids is the
palpebral fissure
b. Palpebral Ligaments
i. Lateral – lateral edge of tarsal plate to bony orbital margin
ii. Medial – medial edge of tarsal plate to lacrimal bone
c. Glands
i. Sebaceous – open into eyelash follicles
ii. Tarsal – aka meibomian glands, modified sebaceous glands, prevent tear
overflow and make eyelids airtight
iii. Ciliary - aka glands of Moll, modified sweat glands open between eyelashes
d. Conjuctiva
i. Palpebral conjunctiva
ii. Superior and inferior fornices
iii. Bulbar conjunctiva – inflammation results in conjunctivitis
iv. Conjuctival sac
v. Palpebral fissure
e. Levator Palpebrae Superioris Muscle – attaches to tarsal plate and skin at aponeurosis
i. Muller’s muscle – raies upper eyelid 2-3 mm with sympathetic input
f. Orbicularis Oculi Muscle – facial nerve
i. Palpebral part
ii. Orbital part
g. Neurovascular
i. Innervation to upper eyelid – CNV1
1. Supratrochlear nerve
2. Supraorbital nerve
3. Infratrochlear nerve
4. Lacrimal nerve
ii. Innervation to lower eyelid – CNV2
1. Infraorbital nerve
F) Lacrimal Apparatus
a. Structure
i. Lacrimal gland – secretes serous fluid, tears, wash into lacrimal lake
ii. Tears flow into superior punctum ->
superior canaliculi ->
common canaliculus ->
lacrimal sac->
nasolacrimal duct
iii. Analog for inferior portion
iv. Blinking contracts orbicularis oculi and squeezes lacrimal sac, pushing tears into
nasolacrimal duct, opening eye relaxes the muscle and refills lacrimal sac
v. Medial to puncta is lacrimal caruncle, skin containing sebaceous glands
b. Sensory Innervation – lacrimal nerve from CNV1, see above
c. Secretomotor Innervation
i. Facial Nerve-> greater petrosal nerve -> nerve of pterygoid canal ->
pterygopalatine ganglion: preganglionic parasympathetic
ii. Maxillary nerve -> pterygopalatine ganglion -> zygomatic nerve (below lacrimal
in orbit): parasympathetic preganglionic
iii. Everyone converges near the lacrimal nerve to innervate the lacrimal gland