Orbits Flashcards
roof of orbit
orbital part of frontal bone
medial wall of orbit
orbital plate of ethmoid, lacrimal, maxilla, and sphenoid
inferior wall of orbit
orbital surface of maxilla
lateral wall of orbit
frontal process of zygomatic bone and greater wing of sphenoid
apex of orbit
optic canal in lesser wing of sphenoid
palpebral conjunctiva
internal surface of eyelid
bulbar conjunctiva
anterior surface of eyeball
conjunctival sac
space bound by the palpebral and bulbar conjunctivae
tarsus
dense bands of CT that form the “skeleton” of eyelids
superior tarsus
upper eyelid; levator palpebrae superioris; superior tarsal muscle; loss of function for either muscle results in ptosis or drooping of the upper eyelid
inferior tarsus
lower eyelid; attached medially to maxilla by medial palpebral ligament; attached laterally to zygomatic by lateral palpebral ligament
tarsal glands
produce lipid secretion to prevent eyelids from sticking together
what keeps the orbit fat contained?
orbital septum
lacrimal apparatus
involved in production, movement, and drainage of fluid from surface of eyeball; includes lacrimal gland, excretory ducts, lacrimal canaliculi, lacrimal sac, and nasolacrimal duct
lacrimal gland
secretes lacrimal fluid; divided into orbital and palpebral parts by tendon of LPS
lacrimal canaliculi
small canals that drain lacrimal fluid from lacrimal lake to lacrimal sac
lacrimal sac
dilated superior part of nasolacrimal duct
nasolacrimal duct
conveys lacrimal fluid to inferior nasal meatus
innervation of lacrimal gland
sensory from lacrimal branch of V1; PNS from facial to greater petrosal nerve to nerve of pterygoid canal to pterygopalatine ganglion which sends fibers to join maxillary nerve to zygomatic nerve to lacrimal nerve to gland; SNS fibers leave internal carotid plexus to form deep petrosal nerve contributing to formation of nerve of pterygoid canal
common tendinous ring
periorbita that thickens around optic canal and central part of SOF: point of origin of rectus muscles
fascial sheath of eyeball
attaches to sclera near optic nerve to edge of cornea blending with investing fascia of muscles
suspensory ligament
lower part of fascial sheath which supports the eyeball
medial check ligament
expansion of investing fascia that covers medial rectus, attaches to lacrimal bone, and restricts movement of medial rectus
lateral check ligament
expansion of investing fascia that covers lateral rectus, attaches to zygomatic bone, and restricts movement of lateral rectus
function of LPS:
elevate superior eyelid
innervation and function of superior tarsal muscles:
sympathetic fibers; help maintain eyelid elevation
eye rotation around vertical axis causes pupil to move:
medially and laterally
eye rotation around transvere axis causes pupil to move:
superiorly and inferiorly
eye rotation around anterior-posterior axis causes pupil to move:
intorsion and extorsion
function of SR
elevation, adduction, and medial rotation
function of MR
adduction
function of IR
depression, adduction, and lateral rotation
function of SO
abduction, depression, and medial rotation
function of IO
abduction, elevation, and lateral rotation
clinical testing of SR
look laterally and upward
clinical testing of IR
look laterally and downward
clinical testing of LR
look laterally
clinical testing of MR
look medially
clinical testing of IO
look medially and upward
clinical testing of SO
look medially and downward
abducent nerve palsy causes eye to:
turn medially
trochlear nerve palsy causes eye to:
turn up and in
oculomotor nerve palsy causes eye to:
turn down and out
blood supply to orbit is mainly from:
mainly from ophthalmic artery (ICA); central artery of the retina, lacrimal, long and short posterior ciliary, supraorbital, anterior and posterior ethmoidal, medial palpebral, dorsal nasal, supratrochlear, anastomotic branch
contribution of blood supply to the structures related to the orbital floor comes from:
infraorbital artery (ECA)
venous drainage of orbit:
superior and inferior ophthalmic veins enter cavernous sinus; inferior ophthalmic can also drain into pterygoid venous plexus; central vein of retina usually drains directly into cavernous sinus
vorticose veins from vascular layer of eyeball drain into:
inferior ophthalmic vein
route by which infections can spread from outside to inside cranial cavity
through ophthalmic veins and cavernous sinus
what travels within optic nerve?
central retinal artery and vein
papilledema
edema of optic disc caused by increased CSF pressure slowing venous return from retinal veins
superior branch of oculomotor nerve innervates:
LPS and SR
inferior branch of oculomotor nerve innervates:
MR, IR, IO, and sends branch to ciliary ganglion
what travels through common tendinous ring?
optic nerve, ophthalmic artery, oculomotor nerve, abducent nerve, nasociliary branch of ophthalmic nerve
ophthalmic nerve
sensory nerve that has lacrimal, frontal, and nasociliary branches
lacrimal nerve
branch of ophthalmic nerve; receives branch from zygomaticotemporal nerve which carries PNS and SNS postganglionic fibers
frontal nerve
branch of ophthalmic nerve; gives off supratrochlear and supraorbital nerves
nasociliary nerve
branch of ophthalmic nerve; gives off sensory root to ciliary ganglion, long ciliary nerves, infratrochlear nerve, and and anterior and posterior ehtmoidal nerves
ciliary ganglion
sensory root from nasociliary nerve; receives presynaptic PNS from oculomotor and sends postsynaptic short ciliary nerves; receives postsynaptic SNS fibers from internal carotid plexus which innervate dilator pupillae muscles
short ciliary nerves
postsynaptic PNS nerves from ciliary ganglion that causes pupil constriction via sphincter pupillae and accommodation of lens via ciliary muscles
eyeball makeup from anterior to posterior:
cornea, anterior chamber, iris and pupil, posterior chamber, lens, vitreous chamber, and retina
fibrous layer of eyeball consists of:
sclera and cornea
sclera
tough, opaque part of fibrous layer that covers posterior 5/6 of eye
cornea
transparent part of fibrous layer covering anterior 1/6 of eye
corneal limbus
angle formed by intersecting curvatures of scleral and cornea at corneoscleral junction
vascular layer of eyeball
AKA uvea or uveal tract; consists of choroid, ciliary body, and iris
choroid
represents 2/3 of vascular layer
ciliary body
extends from anterior border of choroid and completes a ring around eyeball; includes ciliary muscle and ciliary processes
ciliary processes
secretes aqueous humor
contraction of ciliary muscle:
decreases size of ring formed by ciliary body reducing tension on suspensory ligament of lens resulting in accommodation for near vision
iris
colored part of eye containing the pupil
coloboma of iris
a hole or missing portion of iris
nonvisual part of retina
anterior continuation of pigmented layer extending over ciliary body and posterior surface of iris
ora serrata
junction between optic part and nonvisual part of retina
optic part of retina
consists of neural layer which is attached to pigmented layer around optic nerve and ora serrata and pigmented layer which is firmly attached to choroid
fundus of eyeball
internal aspect of posterior part of eyeball where light entering the eye is focused; includes the optic disc, macula lutea, and fovea centralis
optic disc
where optic nerve leaves retina; has no light sensitive receptors (blind spot)
macula lutea
small area with hint of yellow that is lateral to optic disc and contains a central depression containing fovea centralis
fovea centralis
thinnest area but has most visual sensitivity; fewer rods and more cones
rods
dim light, insensitive to color
cones
bright light, sensitive to color
detached retina
detachment of neural layer; results from seepage of fluid between the neural and pigmented layers
anterior chamber
space between the cornea anteriorly and the iris/pupil posteriorly
posterior chamber
between iris/pupil anteriorly and the lens and ciliary body posteriorly
aqueous humor
provides nutrients for avascular cornea and lens; maintains intra-ocular pressure; produced in posterior chamber by ciliary processes and flows into anterior chamber through pupil; absorbed into scleral venous sinus (canal of Schlemm)
glaucoma
condition with increased intra-ocular pressure caused by disruption in flow of aqueous humor
closed-angle glaucoma
iris closes drainage angle and obstructs aqueous outflow
open-angle glaucoma
drainage is open and outflow of aqueous is blocked at scleral venous sinus
vitreous chamber
posterior to lens that is filled with vitreous humor; transmits light, holds retina in place, and supports the lens
capsule of lens is anchored by:
suspensory ligament to ciliary processes
to bring distant objects into focus, lens needs to be:
thinner (less convex)
to bring near objects into focus, lens needs to be:
more convex
presbyopia
with age the lens becomes harder and more flat reducing the focusing power of the lens
cataracts
cloudiness of lens
extracapsular cataract extraction
remove lens but leave capsule
intracapsular lens extractoin
remove lens and capsule
Horner syndrome
results from interruption of cervical sympathetic trunk; causes constriction of pupil, drooping of superior eyelid, redness and increased temperature of the skin, absence of sweating