head: orbit Flashcards
orbit: Pyramid-shaped w/ ________ base +________ apex
Anterolateral base
Posteromedial apex
what angles are the medial and lateral walls of the orbit to each other?
Medial walls parallel
Lateral walls at 90° to each other
what angles are the axis of the orbits at to each other? what about axis of neutral gaze?
Axis of orbits at 45° to each other
Axis of neutral gaze parallel
what lines the orbit?
Lined by periorbita-periosteum of orbit
what bones make up the orbit opening of the face (aka the base) ?
Reinforced portions of frontal, zygomatic, & maxillary bones
what make up the superior wall of the orbit?
Orbital portion of frontal bone
Lesser wing of sphenoid
what bone can you find the anterolateral fossa for lacrimal gland?
orbital portion of frontal bone (forming the superior wall)
where bones are the superior and inferior orbital fissures between? what wall does each separate in the orbit?
superior orbital fissure: optic canal between lesser and greater wings of sphenoid (separates lateral wall from apex)
inferior orbital fissure: between maxilla and greater sphenoid (separates lateral wall from inferior wall)
what 4 bones make up the median wall of the orbit?
Orbital plate of ethmoid
Frontal process of maxillary bone
Lacrimal bone
Frontal bone
what are the two features on the medial wall of the orbit?
lacrimal bone: fossa for nasolacrimal duct
attachment of trochlea for superior oblique
what bones makes up the inferior wall of the orbit?
maxillary
which is the most exposed portion of the orbit (which wall)?
lateral
what bones make up the lateral wall of the orbit?
Frontal process of zygomatic bone
Greater wing of sphenoid
what is the apex of the pyramid that is the orbit ?
Optic canal in lesser wing of sphenoid
what is the palpebra conjunctiva? what does it reflect onto?
internal lining of eyelid (palpebra)
Reflects onto anterior surface of eyeball
which conjunctiva is directly on the sclera and attaches to it from the border of the cornea?
bulbar conjunctiva (vascular)
what is the space between the palpebra + bulbar conjunctiva . what is the significance of this location?
Conjunctival sacs (superior & inferior) - where you administer eyedrops
what is the “tarus”? what do they do?
on inner side of eyelid: Dense connective tissue containing tarsal glands
Secrete lipid to prevent sticking & resist tear drainage
orbital septs extend from _____ to _______ ______. what is their purpose?
Orbital septa extend from tarsus to orbital margin
Limits spread of infection to/from orbit to face (act as barrier)
what muscle is anterior/superficial to tarsus? (on eyelid)
Palpebral portion of orbicularis oculi
what are the medial and lateral canthus of the eye?
Palpebral commissures-medial & lateral junctions
medial/lateral palpebral ligaments extends from where to where? what is the significance of the medial palpebral ligament?
from medial/lateral canthus out to orbital margin(bone)
- Origin & insertion of orbicularis oculi
what 4 structures does the “lacrimal apparatus” include?
- lacrimal gland
- 2 lacrimal papillae
- lacrimal sac
- nasolacrimal duct
lacrimal gland: where is it? what does it contain? what is its purpose?
Fossa of superolateral orbit
8-12 excretory ducts drain into superior conjunctival sac
(Isotonic saline with lysozyme)
Lubricates conjunctiva & cornea
what do the lacrimal papillae/canaliculi do?
Drain tears from lacrimal lake at medial canthus
what is the path of secretomotor innervation of the lacrimal apparatus? ( pregang, enters where and becomes what nerve, synapses, postgang)
PSNS
Preganglionic fibers travel in CN VII (Greater petrosal branch)
Enters pterygoid canal as nerve of pterygoid canal
Synapse in pterygopalatine ganglion (synapse occurs here)
Postganglionic fibers travel in CN V2, then CN V1. after synapse…
CN V2- Infra-orbital
CNV2 -Zygomatic
CN V1 - Lacrimal
eye muscles: which two do elevation, which two do depression?
inferior oblique and superior rectus: elevation
inferior rectus and superior oblique : depression
what is the most superior muscle in the orbit space?
Levator Palpebrae Superioris
Levator Palpebrae Superioris: O, I, A, Inn
O-lesser wing of sphenoid, superior to optic canal
I-tarsus & skin of superior lid
A- Elevates superior lid
Inn- oculomotor nerve (CN III)
superior oblique: O, I, A, In
O-body of sphenoid, tendon redirected by trochlea in superomedial orbit
I-lateral sclera (deep to superior rectus)
A- Abducts, depresses, medially rotates eyeball- summation of abduct and depress = DOWN + OUT
Main action-depression of pupil when adducted
Inn: trochlear nerve (CN IV)
what is the only eye muscle innervated by trochlear CN IV ( not oculomotor nerve CN III)
superior oblique
what 3 axises does the eye move around?
vertical, transverse, AP
inferior oblique muscle: O, I, A, Inn
O-anterior portion of orbital floor near lacrimal fossa of lacrimal bone
I-lateral sclera (deep to lateral rectus)
A- Abducts, elevates, laterally rotates eyeball
Main action-elevation of pupil when abducted
“UP + OUT”
Inn- oculomotor nerve (CN III)
superior rectus muscle: O, I, A, Inn
O-common tendinous ring around optic canal & portion of superior orbital fissure
I-superior sclera
A- Elevates, adducts, medially rotates eyeball -UP + IN
Main action-elevation of pupil
Inne- oculomotor nerve (CN III)
inferior rectus muscle: O,I,A, Inn
O-common tendinous ring around optic canal & portion of superior orbital fissure
I-inferior sclera
A- Depresses, adducts, laterally rotates pupil - DOWN + IN
Main action-depression of pupil
Inn- oculomotor nerve (CN III)
which is the only eye muscle innervated by abducent nerve (CN VI) ( and not oculomotor nerve CN III)
lateral rectus
medial rectus muscle: O, I, A, In
O-common tendinous ring
I-medial sclera
A- Adducts eyeball
Inn- oculomotor nerve (CN III)
lateral rectus muscle: O, I, A, In
O-common tendinous ring
I-lateral sclera
A- Abducts eyeball
Inn- abducent nerve (CN VI)
what eye muscles of movement originate on the common tendinous ring around optic canal?
sup. and inf rectus, medial and lateral rectus
where do all eye muscles for movement insert?
somewhere on the sclera
what is the “common tendinous ring” of the orbit?
Tendons of 4 rectus muscles enclose portion of superior orbital fissure
what are the contents of the “common tendinous ring” ? (5)
- Optic nerve (CN II)
- Ophthalmic artery
- Superior/inferior divisions of oculomotor nerve (CN III)
- Abducent nerve (CN VI)
- Nasociliary nerve (terminal branch of ophthalmic (CN V1) nerve)
what does the nasocilliary nerve do?
from CN V1: Sensory from cornea & sympathetic motor to dilator pupillae
eye movement tests: Initially directing gaze _______ isolates SR for ____, IR for________
laterally (along axis of SR/IR)
SR: elevation
IR: depression
IO (due to….) & SO (due to …) approach eyeball laterally.
IO: anterior origin
AO: redirection by trochlea
eye movement test: Initially directing gaze______ isolates SO for _______, IO for _______
medially (along axis of SO/IO)
SO: depression
IO: elevation
Tests: what are the directions to test: SO, IO, SR, IR ?
SO- IN and down
IO- IN and up
SR- OUT and up
IR - OUT and down
eyeball: what portion of the orbit does it occupy? about how big is it?
Occupies anterior 1/3 of orbit
Approximately 2.5 cm diameter
what prevents retraction of the eyeball into the posterior 2/3 of the orbit?
Retrobulbar fat prevents retraction (inophthalmous)
what is the eyeball suspended in?
Suspended in fascial sheath (Tenon’s capsule) & by bulbar conjunctiva
what three spherical layers/tunics surround the hollow globe that is the eyeball? what structures do each include?
Fibrous layer- sclera + cornea
Vascular layer-uvea: Choroid, ciliary body, & iris
Neural layer-retina
what is the fibrous layer of the eye like? what are the portions of sclera + cornea?
Tough, provides shape & resistance
sclera ( posterior 5/6) cornea ( anterior 1/6)
sclera portion of fibrous layer: what is it like? attachments for what 2 kinds of structures?
Opaque, visible through bulbar conjunctiva
Attachment of intrinsic & extraocular muscles
cornea portion of fibrous layer: what is it like?
Transparent, convex
Avascular, highly innervated (nasociliary branch of CN V1)
Nutrients derived from lacrimal fluid & aqueous humor
what is the function of the cornea ?
Functions in refraction of light entering eyeball
vascular layer: choroid
Choroid-lines most of posterior sclera
Highly vascular (highest perfusion)
Neural retina derives nutrients from choroid capillaries
vascular layer: ciliary body - what is it? what 2 things does it do?
Ring of smooth muscle
- Controls thickness of lens via zonular fibers (suspensory ligament of lens)
- Ciliary processes secrete aqueous humor
what is the anterior continuation of the choroid?
ciliary body
vascular layer: iris- what is it? what does it do?
most anterior aspect of choroid
Contractile diaphragm with central aperture (pupil)
Regulates light entering eyeball
what are the two muscles that are directly under the iris (and help it do its function)
outer radial muscles: dilator pupillae - SNS
inner circular muscles: sphincter pupillae - PSNS
outer radial muscles (dilator pupillae): SNS or PSNS? fxn? fast or slow?
Sympathetic stimulation Dilates pupil (mydriasis) Paradoxically slow
inner circular muscles (sphincter pupillae): SNS or PSNS? fxn? fast or slow?
Parasympathetic stimulation Constricts pupil (miosis) Paradoxically immediate
two parts of the neural layer/tunic? what areas do each line?
optic retina: lines posterior eyeball to ciliary body (“fundus”)
nonoptic retina: lines ciliary body & iris
neural layer: optic retina - two layers
Light-receptive neural layer (external & avascular)
Light absorbing pigmented layer (internal, contains retinal artery)
neural layer: nonoptic retina- one layer
Only pigmented layer
two features of the neural layer/tunic
optic disc + maculae lutea
optic disc: where is it? what is it?
Medial (nasal) portion of fundus
Entry of optic nerve & retinal vessels
No photoreceptors, “blind spot”
maculae lutea: where is it? what is it?
Lateral to optic disc, direct axis from pupil
Highly concentrated cones
Fovea centralis-center of macula
where is the fovea centralis? what is its significance
center of macula - highest visual acuity
what are the compartments of the eye? where does each extend? what type of liquid in each?
anterior: between cornea + lens - filled w/ aqueous humor
posterior: between lens + retina - filled w/ vitreous body
what is the anterior compartment subdivided into?
Subdivided by iris into anterior & posterior chambers
Continuous via pupil
anterior compartment: what produces aqueous humor, what absorbs it?
Ciliary processes in posterior chamber produce aqueous humor
Scleral venous sinus (canal of Schlemm) in anterior chamber absorbs aqueous humor
Intraocular pressure dictated by rates of what?
rates of production + absorption of aqueous humor
what does the vitreous body of the posterior comparment do?
Transmits light to retina & absorbs excess light
Supports lens position
define refraction
Bending of light rays to focus on retina
what do the cornea + lens each do in refraction?
Cornea-major refractive medium, focuses inverted/reversed image
Lens-fine-tunes refraction
what is the shape of the lens? what is it suspended by?
Biconvex, transparent
Suspended by zonular fibers of ciliary body
how do you get distant vision?
Relaxed ciliary body tenses zonular fibers, stretches lens to less convex
how do you get near vision (accommodation)?
Contracted ciliary body relaxes zonular fibers, lens relaxes to more convex
what innervates for near vision?
Parasympathetic via oculomotor nerve
what nerves enter the orbit?
CN II- VI
*(CN V includes V1 and V2)
CN II
visual stimuli to visual cortex (special sensory)
CN III: somatic + autonomic
motor to levator palpebrae superioris, SR, MR, IR, & IO (**all except SO) (somatic motor)
preganglionic PSNS to ciliary ganglion (autonomic)
CN IV : somatic
motor to SO (somatic motor)
CN V: V1 : somatic + autonomic
sensory from face, cornea (somatic sensory); postganglionic PSNS to lacrimal gland, ciliary body, & sphincter pupillae (autonomic);
postganglionic SNS to dilator pupillae (autonomic)
CN V: V2 : somatic + autnomic
sensory from face & scalp (somatic sensory); postganglionic PSNS to lacrimal gland (autonomic)
CN VI : somatic
motor to LR (somatic motor)
which nerves do somatic motor?
CN III, IV, VI
what is the course of optic nerve CN II ? - enters orbit via?, passes through (maintaining what covering)? pierces what? enters retina where?
Enters via optic canal
Passes through tendinous ring of rectus muscles
Maintain meningeal covering & CSF (optic nerve sheath)
Pierce sclera at lamina cribrosa
Enters retina at optic disc
Optic nerve sheath pierced by what?
central artery of retina
where does oculomotor CN III enter the orbit? what does it divide into?
Enters via superior orbital fissure
Divides into superior & inferior divisions
*Both divisions pass through tendinous ring of rectus muscles
CN III superior division - supplies what two muscles?
Levator palpebrae superioris
Superior rectus
CN III inferior division - supplies what 3 muscles, what autonomics?
Medial rectus
Inferior rectus
Inferior oblique
Preganglionic parasympathetic to ciliary ganglion (ciliary body & sphincter pupillae)
course of trochlear nerve CN IV
Enters via superior orbital fissure
DOES NOT pass through tendinous ring of rectus muscles
Supplies superior oblique
course of abducens nerve CN VI
Enters via superior orbital fissure
Passes through tendinous ring of rectus muscles
Supplies lateral rectus
which is the only nerve that does NOT pass through tendinous ring of rectus muscles?
trochlear nerve CN IV
opthalmic nerve CN V1 - what does it supply?
Sensory from upper face & scalp
Sensory from cornea
Conveys postganglionic parasympathetic neurons to lacrimal gland
what are the division of CN V1
Three divisions, all pass through orbit
Frontal
Lacrimal
Nasociliary
CN V1: frontal nerve : course, what it divides into, what it supplies
Courses along roof of orbit
Divides into supratrochlear & supraorbital branches
exits Supraorbital foramen
Supplies portions of face & scalp
CN V1: lacrimal nerve : course? receives fibers from what nerve?
Courses along roof of orbit to reach lacrimal gland & overlying skin
Receives postganglionic PSNS fibers from pterygopalatine ganglion via zygomatic nerve of CN V2
which is the only portion of CN V1 to pass through the tendinous ring with rectus muscles?
CN V1: nasociliary nerve
CN V1: nasociliary nerve: divides into what 3 branches?
Divides into infratrochlear, ethmoidal, & sensory branches from cornea
CN V1: nasociliary nerve: sensory fibers from cornea divide into what?
- Some fibers pass through ciliary ganglion, enter short ciliary nerve
- Some fibers bypass ciliary ganglion, enter long ciliary nerve
- Long ciliary also carries SNS neurons to dilator pupillae
Long ciliary nerves carry sensory fibers from cornea (nasociliary nerve) but ALSO carry what?
SNS neurons to dilator pupillae
ciliary ganglion: SNS or PSNS?
PSNS
three “roots” that enter the ciliary ganglion. what do they each supply?
- Nasociliary-some sensory neurons of CN V1 from cornea
- SNS-vasomotor to eyeball
- PSNS (oculomotor)-preganglionic neurons from CN III
ciliary ganglion- what nerves synapse and leave? what just pass through it?
synapse: PSNS (oculomotor) enter ganglion-> synapse w/ short ciliary-> Postganglionic PSNS neurons to ciliary body & sphincter pupillae
just pass through: Continuation of SNS & sensory nasociliary neurons (no synapse)
maxillary nerve CN V2: what does it supply? delivers postgang from where?
Sensory from mid-face, upper jaw, & anterolateral scalp
-Delivers postganglionic PSNS neurons from pterygopalatine ganglion to lacrimal nerve (CN V1)
what two division of maxillary nerve CN V2 pass through orbit?
Infraorbital
Zygomatic
CN V2 infraorbital nerve: course + supply
Enters via inferior orbital fissure
No branches to eye
Exits via infraorbital foramen
Supplies mid-face & upper jaw
CN V2 zygomatic: where does it enter + supply ?
Enters via inferior orbital fissure
Supply anterolateral face & scalp
CN V2: zygomatic subdivides into what?
Divides into zygomaticotemporal & zygomaticofacial branches
CN V2: zygmogatic nerve has a communicating branch with what nerve? what does it carry in this?
Communicating branch to lacrimal nerve (CN V1)
Postganglionic parasympathetic fibers
ophthalmic artery: what is it a branch of? where does it enter the orbit?
Branch of internal carotid
Enters via optic foramen
what branches come off the ophthalmic artery in the orbit?
- Central artery of retina pierces sheath of optic nerve
Only supply to inner retina - Long & short ciliary braches supply other layers
pupil reactivity: what nerve is the afferent? efferent?
CN II afferent, CN III efferent (constriction)
corneal reflex/blink reflex: what is it? afferent/efferent nerves? what does it assess?
Somatic protective reflex
**Contact cornea (overlying iris/pupil), not sclera (“white of eye”)
CN V1 afferent, CN VII efferent (orbicularis oculi)
Assessment of brain death or neurologic exam
what is horner syndrome
Unilateral miosis, ptosis, & anhydrosis
Constricted pupil, drooping of eyelid, & absence of sweating
Unilateral interruption of sympathetic innervation of head
presbyopia
Lens stiffens, less rounding with ciliary body contraction
Inability to focus on near objects
Hold books at a distance, reading glasses
glaucoma: open vs closed angle
Open angle: Dysfunction or obstruction of scleral venous sinuses
Closed angle: Iris buckles & obstructs outflow
Worsened by anticholinergics
