The Orbit Flashcards
Orbit apex and base
. Apex: posteromed. Orbit, just sup. To optic canal
. Base: formed by ant. Orbital opening (Aditus) and bordered by bones of orbital margin
Orbital margin borders
. Frontal w/ supraorbital notch
. Zygomatic
. Maxilla
Walls of orbit
. Lat. wall: formed by zygomatic and greater wing, separates orbit from temporal and infratemporal fossae
. Med. wall: orbital plate (lamina papyracea) of ethmoid, frontal process of maxilla, lacrimal, minor parts of frontal and orbital process of palatine, separates orbit from ethmoid air cells and sphenoid sinus, lacrimal fossa is formed btw maxilla and lacrimal bone
Roof and floor of orbit
. Roof: orbital plate of frontal and lesser wing, separates orbit from ant. Cranial fossa, frontal sinus separates orbit and ant. Fossa, anterolat. Roof marked by groove for lacrimal gland
. Floor: zygomatic, orbital surface of maxilla, and orbital process, separates orbit from maxillary sinus, infraorbital groove in post. Floor continuous ant. W/ infraorbital canal and foramen
Blowout fractures
. Occurs from blow to the even that inc. infraorbital pressure
. Fractures of thin med. and inf. Walls
. Orbital roof is slightly thicker, but easily penetrated by sharp objects
Openings in orbit
. Optic canal . Sup., orbital fissure . Inf. Orbital fissure . Nasolacrimal canal . Ant. and post. Ethmoidal foramina
Optic canal
. Btw body and lesser wing
. Communication btw orbit and middle cranial fossa
. Transmits optic n. And ophthalmic a.
Sup. Orbital fissure
. Btw greater and lesser wings
. Communication btw orbit and middle cranial fossa
. Transmits oculomotor, trochlear, and abducens nn., branches of ophthalmic n. And ophthalmic vv.
Inf. Orbital fissure
. Btw maxilla and greater wing
. Communication btw orbit and pterygopalatine fossa
. Transmits branches of maxillary n. And infraorbital vessels
Nasolacrimal canal
. Formed btw lacrimal and maxilla
. Communication btw orbit and nasal cavity
. Houses nasolacrimal duct
Ant. And post. Ethmoidal foramina
. Near the frontoethmoidal suture
. Communications btw orbit and ethmoidal air cells
. Transmit ant. And. Post. Ethmoidal nn. And vessels
Periorbita
. Periosteum linings of orbital ca city
. Tough, funnel-shaped sheath surrounding orbital fat, eyeball, and assoc. mm., nn. And vessels
. Fuses w/ dura mater and dural sheath of optic n. At optic canal
. Fuses w/ periosteum of bones forming orbita margin at aditus
Orbital axis
. From apex to geometric center of base (aditus)
. Med. walls of orbits are parallel
. Lat. walls form angle of 90 degrees
. R/L orbital axes form 45 degree angle
Optic axis
. Long axis of eyeball
. From center of cornea to a point just lat. to optic disc
Primary gaze
. R and L optic axes are parallel to each other and to med. orbital walls but angle 23 degrees to orbital axes
Eyelids
. Moveable folds of tissue that protect the eye from light and foreign bodies and help moisten cornea
. Upper lid larger and more mobile
. In primary gaze, partially covers iris
. Separated by palpebral fissure (transverse cleft),
. Meet at med. and lat. angles/canthi
. Anchored to bony orbital margin via med. and lat. palpebral ligaments
Epicanthic fold
. Fold of skin sup. To med. canthus
. Common in young children, characteristic of Down syndrome
Skin of eyelid
. Thin w/ little subQ fat
. Easily bruised
. Eyelashes: cilia, specialized hairs along margins of lids that protect eye
. Sebaceous glands of Zeis: open on ciliary follicles
Muscular layer of eyelid
. Orbicularis oculi- palpebral portion
. Aponeurosis of levator palpebrae sup. M. (Interdigitates w/ orbicularis oculi to insert on skin of upper palpebra) that elevates sup. Palpebra
. Sup/inf. Tarsal mm.: smooth mm. Fibers inserting on sup./inf/tarsal plates, sup. Tarsal m. From deep layer levator palpebrae superioris m., elevate/depress eyelid
Horner’s Syndrome
. CN VII lesions result in inability to clos eye
. Ptosis (dropping of upper eyelid) from enervation of levator palpebrae superioris m. Or interruption of cranial sympathetic innervation
Tarsal plates
. Sup. And inf.
. Rigid plates of dense CT
. Tarsal plates anchored to each other and to bony orbital margins via med.. and lat. palpebral ligaments
. Insertion for tarsal mm. And aponeurosis of levator palpebrae superioris mm.
Tarsal (meibomian) glands
modified sebaceous glands whose secretions reduce lacrimal fluid evaporation
. Prevents tears from overflowing the eyelid margin
Hordeolum externum
. Sty
. Inflammation of sebaceous gland appears as swelling on eyelid margin
Chalazion
. Tarsal cyst
. Inflammation of tarsal glands
Orbital septum
. Fascial septum from tarsal plates to bony orbital margin
. Seals orbital contents from external environment
Conjunctiva
. Continuous mucous membrane that lines deep surface of eyelid (palpebral) and reflects onto ant. Surface (bulbar)
. Palpebral conjunctiva: highly vascularized and reddish
. Bulbar conjunctiva: poorly vascularized and clear
Conjunctival fornices
. Sup. And inf.
. Recesses formed btw palpebral and bulbar conjunctiva
Conjunctival sac
. Formed by conjunctiva when eyelids closed
Lacus lacrimalis
Triangular region of reddish tissue at med. angle
Lacrimal caruncle
. Small, distinct bump at med. end of lacus
Semilunar fold
. Fold of conjunctiva lat. to caruncle
. Vestige of nicitating membrane
Lacrimal gland
. Serious gland housed in a depression in orbital roof
. Drains to sup. Fornix via lacrimal ducts
. Supplied by lacrimal a. (Branch of ophthalmic) and lacrimal n. (Branch of CN V1)
. Parasympathetics inc. lacrimation, sympathetic inhibits it
Lacrimal puncta
. Pores at med. margins of upper and lower eyelids
. Open onto lacrimal canaliculi
Lacrimal canaliculi
. Small ducts that convey lacrimal fluid from lacus lacrimalis to lacrimal sac
Lacrimal sac
. Thin-walled sac w/in lacrimal fossa post. To med. palpebral ligament
Nasolacrimal duct
. W/in nasolacrimal canal
. Drains tears from lacrimal sac to nasal cavity
Blinking function
. Sweeps lacrimal fluid toward lacus lacrimalis
. Facilitates drainage by compressing lacrimal sac against med. palpebral ligament
Sniffing response due to ___
Inc. tear flow into nasal cavity
Extraocular mm. (EOM) axes of motion
. Elevation/depression: transverse axis, movement of optical axis sup./inf.
. Ab/dduction: vertical axis, movement of optical axis away from or toward midline (nose)
. Intorsion/extortion: AP axis, optical axis remains fixed while sup. Surface of eyeball rotates toward or away from midline (nose)
Levator palpebrae superioris m. OIAN
O: lesser wing sup. To optic canal
I: sup. Tarsal plate and skin of upper eyelid
A: elevates upper eyelid
N: oculomotor n. (CN III), sup. Tarsal component innervated by sympathetics
Rectus mm. OIAN
O: all from common annular tendon that encloses optic canal and med. part of sup. Orbital fissure
I: all of sclera of eyeball (named for site)
. Med. rectus AN: oculomotor n., adduction
. Lat. rectus AN: abducens n., abduction
. Sup. Rectus AN: oculomotor n., elevation, adduction, intorsion
. Inf. Rectus AN: oculomotor n., depression, adduction, and extorsion
Superior oblique m. OIAN
O: sphenoid body sup. To common annular tendon, passes med. to levator palpebrae superioris and sup. Rectus
I: tendon loops and passes posterolat. To insert on sclera of posterolat. Eyeball
A: depression, abduction, intorsion
N: trochlear n.
Inferior oblique m. OIAN
O: ant. Floor of orbit, passes posterolat.
I: sclera of posterolat. Eyeball
A: elevation, abduction, extorsion
N: oculomotor n.
Synergistic mm. Pairs for elevation, depression, intorsion, and extorsion
. Elevation: IO and SR . Depression: SO and IR . Intorsion: SR and SO . Extorsion: IR and IO . Pure adduction and abduction from med. and lat. rectus alone
What muscles elevate and depress the abducted eye?
. SR elevates
IR depresses
What muscles elevate and depress adducted eye?
IO elevates
SO depresses
Symptoms of CN III lesion
. Affecte eyeball is abducted, depressed position due to unopposed action of lat. rectus and sup. Oblique
. Sup. Eyelid droops from levator palpebrae paralysis
. Interrupted parasympathetics causes dilated pupil
Trochlear n. Palsy
. Habitual head tilt away from affected side (trochlear torticollis) to compensate for affected eye’s extorted position
. Tilting head toward affected side Bielschowsky head tilt test) elicits compensatory contraction of sup. Rectus and elevation of affected eye
Lacrimal n.
. Branch of V1
. Courses sup. To common annular tendon and last. To levator palpebrae superioris m.
. Sensory to lacrimal gland, sup. Eyelid, and palpebral conjunctive
. Postsynaptic autonomic fibers (sympathetic/parasympathetic fibers) via communication w/ branch of V2
. Relays them to lacrimal gland
Frontal n.
. Branch fo V1
. Course sup. To common annular tendon and levator palpebrae superioris m.
. 2 terminal branches supply sup. Eyelid, palpebral conjunctiva, and skin of forehead
. Supraorbital n. Courses ant. Through supraorbital notch
. Supratrochlear n.: med. to supraorbital n., exits orbit sup. To trochlea
Nasociliary n. And branches
. Branch of V1
. Passes through common annular tendon
. Ant. And post. Ethmoidal nn.: pass med. through ethmoidal foramina, sensory to ethmoidal air cells and sphenoid sinus
. Infratrochlear: inf. To trochlea, pierces orbital septum, sensory to lacrimal apparatus, lower eyelid, and palpebral conjunctive
. Long ciliary nn.: pass ant. And pierce eyeball w/ short ciliary n., sensory to cornea, sclera, and bulbar conjunctive, postsynaptic sympathetic to dilator pupillae
. Ganglionic branches: sensory to ciliary ganglion, relayed to eye via short ciliary n.
Ophthalmic a.
. From internal carotid a.
. Accompanies optic n. Through optic canal
. Passes through common annular tendon
. Has central a. Of retina, long/short post. Ciliary aa., and non-ocular branches
Central a. Of retina
. Pierces optic n. And courses in its center to reach retina
Long/short post. Ciliary aa.
. Pierce sclera (w/ long/short ciliary nn.) to supply sclera, choroid, ciliary body, and iris
Non-ocular branches of ophthalmic a.
. Lacrimal a.: lacrimal gland, eyelids, and palpebral coanjunctiva
. Ant./post. Ethmoid aa.: sphenoid sinus, ethmoidal air cells
. Supraorbital a.: eyelids, palpebral conjunctiva, forehead skin
. Supratrochlear a.: eyelids, palpebral conjunctiva, forehead skin
NO FRONTAL A.
Ophthalmic vv.
. Tributaries correspond to branches of ophthalmic a.
. Sup. Ophthalmic v.: exits orbit through sup. Orbital fissure sup. To common annular tendon, drains cavernous sinus
. Inf. Ophthalmic v.: exits orbit through sup., orbital fissure inf. To common annular tendon, drains cavernous sinus, communicates w/ pterygoid venous plexus via inf. Orbital fissure
What veins provide route of transmission for facial infections to braincase?
. Tributaries of ophthalmic vv. Anastomoses w/ facial v. That goes to braincase
Bulbar fascia (Tenon’s capsule)
. Cup-shaped CT sheath that suspends eyeball w/in orbit
. Fuses w. Dural sheath of optic n. Post.
. Fuses w/ sclera just post. To corneoscleral unction ant.
. Separated from sclera via episcleral space
. Separated from periorbita via orbital fat
. Forms suspensory ligament of eye (sling) inf.
. Pierced by EOM and reflects onto tendons to form CT sheaths
Enucleation
. Surgical removal of eye
. Bulbar fascia is preserved to provide socket for orbital implant
. EOM reattached allowing implant to move in coordination w/ remaining eye
Tunics of eye
. CT layers
. Sclera and cornea outer CT tunic
. Uvea intermediate vascular tunic
. Retina: neurally derived tunic
Sclera
. Dense white CT covering post. 5/6 of ocular globe
. Pierced by optic n., continuous w. Nerve’s dural sheath
. Pierced by ciliary nn. And vessels
Cornea
. Clear, colorless covering of ant. 1/6 of ocular globe
. More curved than sclera
. Corneoscleral junction marked by circular furrow (limbus)
. External corneal epithelium continuous w/ bulbar conjunctiva at limbus
. Avascular (easily transplanted)
. Principal optic surface of eye giving eye 2/3 of refractive power
. Not physiologically adjustable
Ciliary nn.
. Sensory innervation to sclera and cornea
Uvea
. Contains choroid, ciliary body, and iris
. Uvea and external layer of retina supplied by long and shot post. Ciliary aa. And ant. Ciliary branches of aa. To the EOM
Choroid
. Darkly pigmented vascular lining most of sclera
. Firmly adherent to retina, easily separates from sclera
. Choroidal pigments reduce scattering of light w/in eye
Ciliary body
. Ring-shaped, in ant. Eye, continuous post. W/ choroid
Ciliary muscle
Ring of smooth m. Around periphery of iris
. Contracts in response to parasympathetics
Ciliary processes
. Projections from ciliary body
. Grieve rise to suspensory ligament of lens
. Secrete aqueous and vitreous humor, clear fluids that fill chambers of eye
Ciliary zonule of Zinn
. Ring of zonular fibers that make of suspensory ligament of lens
Iris
. Adjustable, pigmented diaphragm ant. To ciliary body
. Color determined by quantity and distribution of pigment
Pupil
. Central aperture of iris
. Size adjusted by antagonistic smooth mm. Under ANS control
Sphincter pupillae
. Parasympathetic innervation via CN III and ciliary ganglion
. Annular smooth mm. Fibers
. Constrict pupil aperture
Dilators pupillae
. Postsynaptic sympathetic fibers from internal carotid plexus via long ciliary nn.
. Radially oriented smooth mm. Fibers
. Dilate pupillary aperture
Optic retina
. Extends from optic disc to just post. Of ciliary body
. Outer pigment layer: tightly bound to choroid
. Inner neural layer: contains rods and cones
Macula lutea
. Centrally located yellowish region
. Region of high visual acuity
. Corresponds to central visual field
. Fovea centralis: center of macula, region of greatest resolution and focal point of eye
Optic disc
. Immediately med. to macula
. Fibers of retinal ganglion cells converge here to form optic n.
. Causes blind spot
. Retinal aa.: branches of central retina a. Radiate from optic disc
Macular degeneration
. Produces visual field defects
. Leading cause of legal blindness in people over 55
. Dry: from age-related changes in macular thickness and pigmentation
. Wet: proliferation of choroidal blood vessels causing bleeding and scarring of macula
Ciliary and iridial retina
. Pigmented epithelium deep to ciliary body and iris
. Not photoreceptive
Ora serrata
. Jagged line post. To ciliary body
,. Marks border w/ optic retina
Vitreous chamber
. Post. To lens
. Contains virtuous body (gelatinous mass formed by protein matrix interspersed w/ watery vitreous humor)
. Gives eye shape and holds retina in place
Ant. Chamber of eye
. Btw cornea and iris
Post. Chamber of eye and aqueous humor
. Btw iris and lens
. Contains watery aqueous humor (so does ant. Chamber)secreted by ciliary processes to nourish avascular cornea and lens
. Circulates from post. To ant. Chamber, drains at iridocorneal angle via sclera venous sinus (canal of Schlemm)
Glaucoma
. Inc in intraocular pressure from failure to aqueous humor drainage
. Primary: open angle, insidious onset, symptomless until damage to optic n. And retina and advanced
. Secondary: closed angle, from acute blockage of sclera venous sinus, accompanied by pain and visual abnormalities
lens
. Transparent, biconvex body suspended btw iris and vitreous body
. Suspended from ciliary body by suspensory ligaments (ciliary zonule) that attach to lens capsule
. Thickness and curvature adjusted by ciliary m.
. When m. Contracts (parasympathetic), the suspensory ligaments relax and lens is more spherical for near focus
. When m. Relaxes, the ligaments tighten and lens resumes flattened shape
Accommodation for near vision
. Requires coordinated thickening of lens (ciliary mm.) and constriction of pupil (sphincter pupillae)
. Lens loses flexibility w/ age causing loss of accommodation (presbyopia) and need for reading glasses
Cataracts
. Clouding of lens
. Due to aging and/or UV damage
