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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