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22 Cards in this Set
- Front
- Back
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Orbit
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contains:
1. eyeball 2. muscles 3. nerves 4. lacrimal apparatus * apex-posterior in region of optic canal * base-squarish quadrilateral opening onto face |
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4 margins of orbit:
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1. supraorbital-frontal bone
2. lateral-zygomatic bone 3. infraorbital-zygomatic and maxillary bones 4. medial-frontal process of maxilla and little bit of lacrimal bone |
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Walls of orbit:
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1. roof: orbital plate of frontal with lesser wing of sphenoid posterior
2. floor: orbital surface of maxillary, zygomatic and palatine process contributing 3. medial: orbital plate of ethmoid (thin); also called lamina papyracia 4. lateral: greater wing and zygomatic (thicker) |
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major foramina and fissures:
1. optic canal |
*transmits optic nerve (CNII)
*ophthalmic artery (ICA) |
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2. superior orbital fissure
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*elongated slit separates roof and lateral wall
*lies between greater and lesser wings *connects with middle cranial fossa *CNIII, IV, VI (all motor) *branches of CNV1 (from ophthalmic) *ophthalmic vein |
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3. inferior orbital fissure
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*between floor and lateral wall
*allows communication with both infratemporal and pterygopalatine fossas *infraorbital nerve (continuation of maxillary-V2), artery (br of maxillary) , and vein *zygomatic nerve (from V2); primarily cutaneous nerve f skin of face and temple *run in infraorbital groove on floor and emerge through infraorbital foramen |
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4. anterior and posterior ethmoidal foramina
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*medial wall, close to jnctn of frontal and ethmoid bones
*anterior and posterior ethmoidal nerves and vessels *nerves from branches of V1 |
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5. lacrimal gland
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*lies in anterior, superolateral corner of orbit in depression of frontal bone
*anteriorly, fossa for lacrimal sac formed by lacrimal and maxillary bones *nasolacrimal canal contains duct-begins at floor of orbit and runs down into nasal cavity |
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Clinical Importance:
paranasal air sinuses and bony orbit |
1. superiorly, frontal air sinus; frontal lobe lies right on orbital plate of frontal bone-sharp object could injure brain
2. inferiorly, maxillary sinus is separated from floor by thin plate of bone-"blowout fracture" causes eyeball to sink into sinus, causing double vision (diplopia); also infections can spread 3. medially, a)ethmoidal air cells; potential damage to optic nerve when trying to get to air cells; b)posteriorly, sphenoid sinus related to medial wall 4. laterally, surgeons approach orbit through lateral wall (temporal fossa and temporalis muscle), which is associated with middle cranial fossa (temporal lobes of brain) |
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Retina
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1. optic part has photo-receptors (rods and cones)
2. Blind spot-layer of ganglion cell axons converges at optic disc (papilla), then turn posteriorly leaving retina to constitute optic nerve; No rods or cones **outgrowth of brain **optic nerve is a nerve tract that connects one part of brain with another *surrounded by 3 layers of meninges |
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Optic Nerve
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*contains central artery and vein of the retina
*artery must pierce all 3 meningeal layers *dura and arachnoid maters form outer sheath *pia form inner sheath *extension of subarachnoid space surrounding it, called intervaginal space a. contains CSF b. if CSF pressure rises, optic nerve will be affected c. vein vulnerable to pressure, causes optic disc to swell *papilledema could be diagnostic sign related to brain tumors and intracranial pressure increase *special sensory nerve-SSA |
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Muscles that move eyeball
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4 rectus muscle:
a)superior, inferior, lateral , medial *all originate from common tendonous ring (annular ring) *as pass anteriorly, diverge and insert into anterior part of sclera just behind jnctn with cornea 2 oblique muscles: b)superior-originates from sphenoid bone in posterior orbit and runs anteriorly along medial wall; passes thru cartilaginous pulley called trochlea to changes course to run posterior laterally and inserting into posterolateral part of sclera c)inferior-arises from anterior medial floor near nasolacrimal canal and runs posterolaterally under eyeball to insert into sclera |
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3 major axes of eyeball:
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1. Vertical:
a) ADduction-medial, superior, inferior rectus muscles b) ABduction-lateral rectus, inferior and superior obliques 2. Transverse: a)Elevators: superior rectus and inferior oblique b) Depressors: inferior rectus and superior oblique 3. Anterior-Posterior a) Intorsion: superior oblique and rectus b) Extorsion: inferior oblique and rectus |
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Eye movement: Net effect
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**eye ADducted: inferior oblique will elevate eye
**eye ABducted: superior rectus elevates |
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Innervation of eye muscles:
SO4 LR6 R3 |
1. Superior Oblique-only muscle innervated by CNIV (trochlear nerve); comes off midbrain and runs thru SOF
2. Lateral Rectus innervated by CNVI (abducent nerve); runs thru SOF; injury to nerve will cause eye to turn inward 3. All other extrinsic muscles innervated by CNIII (occulomotor nerve); CNIII splits just before entering orbit into: a)superior division: superior rectus and levator palpebrae superioris b)inferior division: inferior rectus, oblique, and medial rectus |
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Sensory nerves of orbit:
branches of Ophthalmic nerve (V1) |
*V1 arises from trigeminal ganglion in middle cranial fossa and continues toward supraorbital fissure embedded in dura mater of lateral wall of cavernous sinus
*purely sensory nerve (GSA) *sympathetic fibers from Internal Carotid plexus join the V1 to innervate the dilator pupili muscle *long ciliary nerves originate from V1 *short ciliary nerves originate from CNIII |
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Branches of Ophthalmic nerve (NFL)
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1. Frontal: very superficial, just above levator palpebrae superioris
a)supratrochlear-small, medially located b)supraorbital-laterally located; branches into medial and lateral branches **both nerves are GSA that supply skin of upper eyelid, forehead, and scalp; supraorbital also supplies linig of frontal air sinus 2. Lacrimal: very thin, runs on lateral wall of orbit above lateral rectus and runs to lacrimal gland *has palpebral branch which innervates skin of eyelid *picks up postsynaptic parasympathetic fibers before reaching gland (from zygomatic nerve) 3. Nasociliary: deep *takes oblique course from lateral to medial running just superiorly to optic nerve *gives off long ciliary nerves *GSA go to eyeball fro sensation, not vision *have post-synaptic sympathetics from Internal Carotid plexus that go to dilator pupili *anterior and posterior ethmoidal nerves-leaves orbit thru anterior and posterior foramen; innervate mucosa lining of ethmoidal air cells *anterior ethmoidal nerve enters and innervates nasal cavity for general sensation; emerges on teh nose and supplies the skin of lower part of external nose (external nasal nerve) 4. infratrochlear: other terminal branch; exits orbit below trochlea *innervates lacrimal sac and general sensation for skin on upper half of nose |
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Ciliary ganglion
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*should find it more laterally, between optic nerve and lateral rectus muscle
*in posterior part of orbit |
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Vessel of orbit
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1. ophthalmic artery: from ICA in middle cranial fossa
*enters orbit with optic nerve thru canal *runs obliquely from lateral to medial, and it runs parallel to nasociliary nerve **Numerous branches: 1. Ocular branches-supplies the eye itself (a. posterior ciliary arteries); b. central artery of retina-pierces optic nerve (sole supply to retina) 2. orbital branches-includes: a. lacrimal-to the gland b. supratrochlear & supraorbital-forehead/scalp c. ethmoidal-nasal cavity d. muscular branches-muscles of orbit e. dorsal nasal-dorsum of nose |
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Venous drainage: ophthalmic veins
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*superior and inferior ophthalmic veins drain the orbit into cavernous sinus posteriorly
*tributaries follow arteries *vorticose veins drain the choroids of eye, which drain into ophthalmic *ophthalmic veins communicate with angular vein anteriorly, which is path for spread of infection from face *inferior ophthalmic vein also communicates thru inferior orbitalfissure with pterygoid venous plexus in infratemporal fossa; another pathway for infection to spread |
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Intrinsic muscles of eye:
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**smooth, involuntary muscle
1. ciliary body: attached to lens by fibers called ciliary zonule or suspensory lig of lens a)contraction of body/muscle relaxes tension in ciliary zonule allowing lens to become more spherical; shortens focal length for nearby objects (accomodation) Iris contains 2 muscles: 1. sphincter pupili: circular and surrounds pupil a) when contracts, constricts pupil and makes smaller, less light to reach retina 2. dilator pupili: antagonist of sphincter pupili a) dilates pupil (mydriasis) *all under autonomics *ciliary muscle and sphincter are under parasympathetics (CNIII) by oculomotor root of ciliary ganglion *presynaptic travel with root to synapse on ciliary ganglion *postsynaptic travel through 5-6 ciliary nerves to reach eyeball via wall of eyeball *dilator is sympathetic *presynaptic in lateral horn of upper 3 thoracic cord segments; leave via white rami communicantes to ascend to cervical sympathetic trunk *synapse occurs in uppermost ganglion of trunk (superior cervical) *postsynaptics travel up ICA form plexus around it called IC plexus *some fibers hitch ride with V1 out of plexus and enters orbit and gives off long ciliary nerves Different pathway: *some sympathetic neurons travel along ophthalmic artery and exit ciliary ganglion via sympathetic root *fibers pass right through ganglion and use short ciliary nerves to reach dilator **both long and short ciliary nerves have postsynaptic sympathetics, but only short have postsynaptic parasympathetics |
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Extrinsic muscles:
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*skeletal, voluntary muscles
1. levator palpebrai superioris: striated a) inserts into skin ofupper eyelid and into superior tarsal plate b) innervated by CNIII 2. superior tarsal: elevates eyelid a) under autonomic control (sympathetic) **CC: ptosis, drooping of eyelid can be caused by damage to CNIII, paralysis of either forementioned muscles |
