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58 Cards in this Set
- Front
- Back
Fasciae: Cranial dura mater continues into the orbit to form?
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Periorbita, Muscle Fascia, check ligaments, and optic nerve sheath
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Periorbita
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The perisoteal lining of the roof, floor, and walls of the orbit
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Muscle Fascia
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The fascia of the extraocular muscles
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Check Ligaments
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Ligaments that maintain eye movements within normal limits
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Optic Nerve sheath
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-outer membranous portion of optic nerve
- consists of extensions of the dura mater, arachnoid membrane, and pia mater - contains space occupied by CSF; central retinal artery and vein pass through space and layers of optic nerve sheath |
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Tenon's Capsule
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- encloses posterior 2/3 of sclera and provides for smooth movement of the eyeball. (The bulbar conjunctiva covers anterior 1/3 of sclera)
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Eye Movements
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-Rotation around transverse axis = elevation/depression
- Rotation around Vertical axis = abduction/adducion. - Rotation around Anterior/posterior axis = intorsion/extorsion |
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Muscles of the Orbit
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Extraocular muscles: striated mm. that insert into sclera of the eye and produce eyeball movement (SR, IR, SO, IO, MR, LR)
Other Muscles: Levator palpebrae superioris m. (striated), Mueller's m.(smooth m.), and within the iris ; sphincter pupillae, and dilator pupillae (smooth mm.). |
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Extraocular mm. Continued
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- Rectus (straight) mm. originate from the common ring tendon that anchors the mm. to the back of the orbit.
- Common ring tendon encircles part of the optic foramen and superior orbital fissure. - IO m originates frm anterior-medial aspect of orbit floor. - SO has a trochlea (pulley mechanism) that changes the direction of pull of muslce on eyeball. |
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Superior Rectus m.
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Innervation: Oculomotor nerve (CN III)
Action: Elevates eye |
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Inferior Rectus m.
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Innervation: Oculomotor n. (CN III).
Action: Depresses eye. |
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Inferior Oblique m.
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Innervation: Oculomotor n. ( CN III).
Action: Elevation and extorsion of eye. |
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Medial Rectus m.
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Innervation: Oculomotor n. (CN III).
Action: Adducts eye. |
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Lateral rectus m.
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Innervation: Abducens n. (CN VI).
Action: Abducts eye. |
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Superior Oblique m.
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Innervation: Trochlear n. (CN IV).
Action: Depression and intorsion of eye. |
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Levator Palpebrae superioris m. and Sphinctor Pupillae m.
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Innervation: Oculomotor n. via parasympathetic fibers: Pre-CN 3, Post-Ciliary Ganglion.
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Dilator Pupillae m. and Mueller's m.
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Innervated by sympathetic nerve fibers: Pre-T1-T3 spinal nerves and Post-Superior Cervical Ganglion
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Innervation Sources to Eye
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-Oculomotor n. gives off oculomotor root (parasympathetic) via Ciliary ganglion to eye.
- Superior cervical ganglion (sympathetic) over internal carotid a. to eye. - Nasociliary n. = ganglionic branch (sensory) passing through ciliary ganglion + long ciliary n. (sensory) passing directly to eye. |
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Short Ciliary n.
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Nerve containing parasympathetic (ciliary ganglion), sympathetic (superior cervical ganglion), and sensory fibers (nasociliary n.) formed after fibers passed through ciliary ganglion.
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Intraocular mm. (3)
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- smooth mm.
- sphincter pupillae m, ciliary body m, and dilator pupillae m. |
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Sphincter Pupillae m.
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- found in Iris
- cirlcular, parasymp., CN 3 Action: Constricts pupil Injury: Mydriasis ( fixed, dilated pupil) |
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Ciliary Body m.
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- cicular component, parasymp., CN 3
Action: Constricts eyeball to thicken lens. Injury: Diminishes near vision. |
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Dilator Pupillae m.
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- Radial, sympathetic, Superior Cervical ganglion.
Action: Dilates pupil Injury: Miosis (pupil constriction). |
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Diplopia (double vision) during lateral gaze eye movements (left and right)
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Could be caused by weaknes of active mm. ; Lateral and Medial rectus mm.
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Lateral Rectus m. weakness
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CN 6 dysfunction (Abducens n.) = Medial strabysmus, adducted eye.
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Medial Rectus m. weakness
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CN 3 dysfunction (Oculomotor n.) = Lateral strabysmus, abducted eye + dilated pupil- eyelid ptosis- disruption of near vision.
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H testing method
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Determines muscle weakness of the elavators of the eye (superior rectus/ inferior oblique) and the depressors of the eye (Inferior rectus/ superior oblique)
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Best elevators and depressors in an abduction position of eyes
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Rectus mm.
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Best elevators and depressors in an adduction position of eyes
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Oblique mm.
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Superior Oblique m. weakness
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- Dysfunction of trichlear n.
- frequently leads to head tilt to the side opposite the weakness. |
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Damage to Right Oculomotor n. (CN III)
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A.: Paralysis of levator palpebrae superioris = ptosis of upper eyelid.
B.: Paralysis of sphincter pupillae m. = mydriasis and lateral strabysmus C.: Paralysis of medial rectus m. = No adduction. D.: Eye abducts to side of lesion due to functioning lateral rectus m. E.: paralysis of superior rectus m. = No upward movement of R. eye F.: Superior oblique m. can not depress abducted eye = No downward movement of eye. |
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Damage to Left Trochlear n. (CN IV)
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- Left superior oblique m. paralysis
- extorted left eye, causing double vision. - head tilts to unaffected side, right eye intorts. - Difficulty depressing eyeball when turned inward - Difficulty walking down stairs when eyes need to be turned downward and inward. |
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Damage to Right Abducens n. (CN IV)
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- Lower motor neuron paralysis of lateral rectus m.
- looking straight ahead, affected eye is slightly adducted (medial strabysmus) - On lateral gaze to normal side, affected eye adducts normally. - On lateral gaze to damaged side, affected eye fails to abduct; causing diplopia. |
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Sensory Nerves entering Orbit
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- Division (V1) of Trigeminal n.
NFL - Nasociliary n. (crosses over Optic n. from lateral to medial) - Frontal n. - Lacrimal n. |
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Branches of Opthalmic a. to Know
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- Supraorbital a.
- Lacrimal a. -Central retinal a ( first branch of opthalmic a., becomes located in optic n. and retina) -Ciliary aa. ( to eyeball) -Anterior Ethmoidal a. - Also Superior Opthalmic vein - |
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Course of Opthalmic a.
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Crosses over optic n. from lateral to medial, course and branches similar to nasociliary n.
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Ciliary aa.
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Form arterial plexus in choroid layer, which supplies, by diffusion, the photoreceptor cells
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Fovea Centralis (part of Retina)
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-Visual acuity area
- Cone receptors (for daylight vision) - Color vision |
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Central retinal a. branches
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-Supply retina near vitreous body
- Radiate out from optic disc |
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Cause of Papilledema (swelling of optic papilla)
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-Collapse of the central retinal vein as it passes through the fluid space in the optic n. sheath
- With increased intracranial pressure |
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Frequent results of increased intracranial pressure
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-papilledema
-medial strabysmus |
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Glaucoma
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- condition resulting from increased intraocular pressure.
- usually caused by impaired outflow of its drainage from anterior chamber. - Can result in retinal and optic n. damage. |
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Aqueous Humor Flow
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1.) Secreted by ciliary body epithelium
2.) posterior chamber 3.) Pupil 4.) Anterior chamber 5.) Trabecular meshwork 6.) Absorbed by Canal of Schlemm |
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Middle Vascular Coat (Uvea)
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Formed by Choroid, Ciliary body, and Iris.
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Near vision adjustment
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- Due to Oculomotor n. activity
- Accommodation of lens = contraction of ciliary body m. constricting the eyeball---- releases tension of zonule fibers--- allows lens to become rounded and thicker---- to focus divergent near light rays onto fovea centralis. Other features = convergence of eyes and pupillary constriction |
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Distant vision
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- Unnaccommodated
- Ciliary muscles relaxed |
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Lacrimal n. (V1)
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- most lateral of three nerves and is directed towards lacrimal gland
-receives communicating branches from pterygopalatine ganglion (parasympathetic), seceretomotor in function - secretion of gland due to Facial n. |
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Frontal n. (V1)
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- largest and middle one of three nerves
- extends towards superior orbital margin - larger branch is the Supraorbital n. |
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Trochlear n. (CN IV)
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- most medial of the three nerves
- passes over levator palpebrae superioris m. to enter border of superior oblique m. |
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Three nerves positioned superiorly in Orbit
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Lacrimal n., Frontal n., and Trochlear n.
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Three nerves located on deeper plane, enter orbit through part of superior orbital fissure and enclosed by common ring tendon
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Oculomotor n., Abducens n., and Nasociliary n.
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Oculomotor n. (CN III)
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- located lateral to optic n. and divides into superior and inferior divisions.
- Inferior division has a branch (oculomotor root) containing preganglionic parasympathetic nerve fibers which synapse on the ciliary ganglion. |
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Ciliary ganglion
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-Small parasympathetic ganglion located between the lateral rectus m. and optic n. ~2cm. from back of orbit
- postganglionic parasymp. fibers innervate two intraocular mm. (sphinctor pupillae m. and ciliary body m.) |
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Abducens n. (CN VI)
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- located on medial surface of lateral rectus m.
- innervates lateral rectus m. |
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Nasociliary n.
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- sensory branch of opthalmic division of the trigeminal n.
- branches = ganglionic branch, long ciliary n., posterior/anterior ethmoidal nn. |
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Long ciliary n.
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- branch of Nasociliary n.
- pass from nasociliary n. directly to eyeball. |
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Posterior and Anterior Ethmoidal nn.
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- enter ethmoidal air cells through foramina in media wall of orbit
- supply sensory innervation to sphenoid sinus and ethmoid air cells - anterior ethmoidal n. has additional distribution to anterior nasal cavity and skin of lower part of nose. |
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Opthalmic a.
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- branch of internal carotid a.
- enters orbit by passing through optic canal in company with optic n. - first branch is central retinal a., which enters the optic n. with central retinal v. at mid-orbital course of the nerve - enters the eyeball at optic papilla and gives rise to 4 branches which supply the quadrants of the retina. |