Orbit and Cavernous Sinus Flashcards
What 7 bones make up the orbit?
Frontal, Sphenoid, Maxilla, Lacrimal, Ethmoid, Zygomatic, Palatine
What 4 areas can the orbit be divided into?
roof, medial and lateral walls, and floor
What bones form the roof of the orbit?
mosty frontal, portion of sphenoid toward the apex
What bones form the medial wall of the orbit?
Frontal bone forms superior portion - maxilla: frontal process of maxilla; will form anterior portion of lacrimal fossa - lacrimal bone: entire bone; will form posterior portion of lacrimal fossa - ethmoid bone: forms majority of medial wall - sphenoid: towards the apex
What bones form the lateral wall of the orbit?
Zygomatic bone anteriorly - Sphenoid posteriorly
What bones make up the floor of the orbit?
Maxilla: majority of floor - Zygomatic bone: anterolaterally - Palatine bone: posteromedially
What are the bony structures of the orbit?
optic canal, superior orbital fissure, inferior orbital fissure, anterior and posterior ethmoidal foramina, lacrimal fossa
What passes through the optic canal?
optic n. (CN II), ophthalmic a.
What passes through the superior orbital fissure?
CN III, IV, V1, VI, and ophthalmic vv. (sup., and inf.)
What passes through the inferior orbital fissure?
infra-orbital n. and zygomatic n. (V2), and the connection between the pterygopalatine fossa and orbit
What passes through the anterior and posterior ethmoidal foramina?
anterior and posterior ethmoidal neurovasculature
What passes through the lacrimal fossa?
nasolacrimal sac
What are the tissues of the eyelid superficial to deep?
Skin, subcutaneous tissue, palpebral fibers of orbicularis oculi, tarso-facial layers, then palpebral conjunctiva
What is the skin of the eyelid continuous with?
the conjuctiva
what is contained within the subcutaneous tissue?
a small amount of adipose tissue
What is the tarso-facial layer composed of?
tarsal plates, medial & lateral palpebral ligaments, tarsal glands, aponeurosis of levator palpebrae superioris m. (superior eyelid only), superior & inferior tarsal mm.
What parts is the conjunctiva split in to?
marginal, tarsal, and orbital parts
what is the conjunctiva?
a delicate mucous membrane that lines the eyelids and covers the anterior aspect of the eyeball (excepting the cornea and pupil)
What covers the eyeball? what lines the eyelids?
the bulbar conjunctiva ; the palpebral conjunctiva
What are the conjunctive fornices?
the inferior and superior fornices are the reflections of conjunctiva from bulbar to palpebral conjunctiva
What is the conjunctival sac?
the potential space between bulbar and palpebral conjunctiva.
Where is the lacrimal gland located?
superolateral margin of the orbit, within the lacrimal fossa of the frontal bone.
What muscles does the lacrimal gland sit between?
sits between the aponeurosis for levator palpebrae superioris m. (medial to the gland) and the lateral rectus m. (inferior to the gland)
Where does the lacrimal gland secrete into?
into the conjunctival sac along the lateral margin of the superior fornix
What is the flow of tear fluid?
conducted across the conjunctiva and accumulates in the lacrimal lake in the medial canthus
What structure is deep to the lacrimal lake?
the lacrimal caruncle
What structures are located superior and inferior to the lacrimal lake? What do they host?
lacrimal papillae : lacrimal puncta (pores) which tear fluid flows in to
How is fluid conducted from the lacrimal puncta?
via superior and inferior canaliculi into the lacrimal sac
What is the superior dilation of the nasolacrimal duct?
the lacrimal sac
Where does the lacrimal sac lie?
in the lacrimal groove of the lacrimal bone
What conducts tears into the inferior nasal meatus?
The nasolacrimal duct
What is the route of lacrimal fluid from start to finish?
lacrimal gland → conjunctival sac → lacrimal lake → lacrimal papillae → lacrimal puncta → lacrimal canaliculi (superior & inferior) → lacrimal sac → nasolacrimal duct → inferior nasal meatus
What is the parasympathetic pathway of the lacrimal gland?
After ganglion, they hitchhike the maxillary nerve (V2) to the zygomaticotemporal n., then lacrimal n., then gland
What is the “classic condition” by which the lacrimal gland receives postganglionic parasympathetic fibers?
pterygopalatine ganglion > V2 > zygomaticotemporal brs. > lacrimal n. > lacrimal gland
What is the more common way by which postganglionic parasympathetic fibers innervate the lacrimal gland?
pterygopalatine ganglion > zygomaticotemporal brs. > lacrimal gland
what does the fibrous portion of the eye provide?
structure and strength to the eyeball
What does the fibrous layer of the eye consist of?
the cornea and sclera
What is the sclera? what is it referred to as commonly?
The sclera covers the majority of the eyeball, is often referred to as the “white of the eye.” It is the insertion site for extra-ocular and intrinsic eye muscles.
what is the cornea?
The cornea covers the anterior portion of the eye (approximately ⅙th of the anterior eye) is completely avascular, sensitive to touch, and is the main refractive index of the eye.
What three stuctures make up the uvea (vascular portion of the eye)?
choroid, ciliary body, and iris
What is the iris?
a diaphragm located on the anterior surface of the lens
What part of the eye is important for transmitting light?
the pupil
What portions of the eye has color? What is the black portion?
Iris : Pupil
What muscles control the pupil?
sphincter pupillae (contracts pupil, parasympathetically-controlled) and dilator pupillae (dilates pupil, sympathetically-controlled).
what composes the inner layer of the eye?
the “neural” layer is composed of the neural retina.
How many layers is the retina composed of? What is contained in those layers?
10 : specialized receptors (rods and cones) as well as interneurons, glia, and ganglion cells
the axons of the ganglion cells exit the retina as the ___________.
optic nerve CN II
What is the main source of blood to the retina?
the retinal a.
How does the retinal a. get to the retina?
it travels within the optic nerve and is a branch of the ophthalmic a.
what are the extra-ocular muscles of the eye?
levator palpebrae superioris m., superior oblique m., superior rectus m., lateral rectus m., medial rectus m., inferior rectus m., inferior oblique m.
What extra-oricular mm. have their origen and insertion at the common anular tendon, and the sclera their respective postion?
the rectus mm. (superior, inferior, lateral, medial)
where do the rectus mm. of the eye originate and insert?
origen: common anular tendon - insertion: Sclera of eye (at respective position ie. superior sclera of eye, etc.)
What extra-ocular m. are not innervated by the occulomoter? what are they innervated by?
Superior oblique m. (trochlear CN IV) and lateral rectus (Abducens CN VI)
What extra-ocular mm. are innervated by the superior division of the occulomotor n.? inferior division?
Levator palpebrae superioris m., and superior rectus m. ——- Medial rectus m., inferior rectus m., and inferior oblique m.
What are the origens of the levator palpebrae superioris and superior oblique mm.?
Apex of the orbit
What muscle does not have an insertion on the sclera of the eye? What is its insertion?
Levator palpebrae superioris m. : superior tarsal plate and tarso-fascial layer
Superior oblique m. insertion?
Sclera of posterosuperior eye
inferior oblique m. origen and insertion
Orbital surface of the maxilla on the floor of the orbit : Sclera of inferior eye
levator palperal superioris m. actions
elevation of upper eyelid
superior oblique m. actions
Abduction, depression, and intorsion (medial rotation) of the eye
Superior rectus m. actions
Adduction, elevation, and intorsion of the eye
Lateral rectus/medial rectus mm. actions
medial: adduction — lateral: abduction
inferior rectus m. actions
Adduction, depression, and extorsion (lateral rotation) of the eye
inferior oblique m. actions
Abduction, elevation, extorsion of the eye
both oblique muslces are responsible for ____________ of the eye.
abduction
The superior and inferior rectus mm. both__________ the eye.
adduct
SUPERIOR oblique and rectus mm. both are responsible for _____________ of the eye.
intorsion
INFERIOR oblique and rectus mm. are both responsible for ______________ of the eye.
extorsion
what is the trochlea?
a fibrocartilaginous loop (pulley) that attaches to the trochlear fossa of the frontal bone
How does the distal tendon of the superior oblique m. get to its insertion point?
it runs through the trochlea before inserting on the posterosuperior sclera of the eye.
what is the common anular tendon also referred to as? what does it encircle?
the common tendinous ring : the optic n., oculomotor n., and abducens n., nasociliary n., and ophthalmic a.
What are the main nerves that send branches to innervate the orbit and its contents?
Optic n. (CN II), Oculomotor (CN III), Trochlear (CN IV), Ophthalmic n. (V1), Abducens (CN VI), Short ciliary nn., Ciliary ganglion
What branches of the ophthalmic n. innervate the orbit and its contents?
FRONTAL N. and brs.: supra-orbital, supra-trochlear, lacrimal n. — NASOCILIARY N. and brs.: long ciliary nn., anterior/posterior ethmoidal nn., infratrochlear n., communicating branch —
What does the frontal n. serve?
afferently serves the medial upper eyelid (skin & conjunctiva), skin of the forehead, and frontal sinus mucosa
Where can the frontal n. be found?
superior to the levator palpebrae superioris m.
What are the two most anterior branches of the frontal n.?
the supraorbital (lateral), and supratrochlear (medial) nn.
What does the supra trochlear n. serve?
passes superior to the trochlea of the superior oblique m. to afferently serve the skin of the medial forehead, and skin and conjunctiva of the medial superior eye.
What does the supra-orbital n. serve?
supra-orbital n. further divides into medial and lateral branches, which afferently serve the mucosa of the frontal sinus, skin of the lateral forehead, and skin and conjunctiva of the lateral superior eye
Where does the supraorbital nerve pass through to get to its innervation point?
the supraorbital foramen or notch
Where can the lacrimal n. be found? how large is it? where does it enter the orbit?
the smallest branch of the ophthalmic. It can be found superior to the lateral rectus m.. It enters through the superior orbital fissure.
what does the communicating branch of the nasociliary n. transmit?
afferent fibers from the eye via short ciliary nn.
What does the infratrochlear n. provide?
sensory innervation to conjunctiva, skin of eyelids, lacrimal caruncle and sac, and side of nose.
Where can the infratrochlear n. be found?
exiting the orbit below the trochlea of the superior oblique m.
the anterior and posterior ethmoidal nn. exit the orbit via the __________________.
anterior and posterior ethmoidal foramina.
What are the long ciliary nn. responsible for?
These branches carry afferent fibers from the eye and postganglionic sympathetic fibers to the dilator pupillae muscle of the eye.
How does the oculomotor n. get to the orbit?
arises from the midbrain, travels within the lateral wall of the cavernous sinus, divides into superior and inferior divisions, and these divisions enter the orbit through the superior optic fissure
What nerves separate the superior and inferior branches of the oculomotor n?
nasociliary n. (V1) and optic n.
How is the oculomotor n. related to the ciliary ganglion?
transmits preganglionic parasympathetic fibers to it destined for sphincter pupillae muscles and ciliary muscles
What 3 types of fibers does the short ciliary nn. transmit between the eye and ciliary ganglion?
- afferent fibers from eye > ciliary ganglion > nasociliary n (V1)
- post gang. parasyms. from ganglion for ciliary and sphincter pupallae mm. (pregang from oculomotor)
- post gang. sym from perivascular plexuses for intraocular vessels
what is the ciliary ganglion?
a peripheral parasympathetic ganglion for intra-ocular mm.
where can the ciliary ganglion be found?
lateral aspect of optic n. near the apex of orbit
What are the 3 conduits to/from the PNS that relate to the ciliary ganglion?
nasociliary n (V1) - afferent from the eye through ganglion to nasociliary (V1)
oculomotor (V`1) - transmits preganglionic parasympathetic fibers to the ciliary ganglion
sympathetics - postganglionic sympathetic fibers and transmited to and through the ganglion from perivascular plexuses of the interanal carotid artery
how does the optic n. get to the eye?
through the optic canal then pierces the sclera
what does the optic n. do?
special somatic afferent - vision
how does the abducens get from the brainstem to the orbit?
the abducens (CN VI) leaves its spot on the brainstem and travels THROUGH the cavernous sinus, and enters the orbit through the superior orbital fissure (and through the comon anular tendon).
What is the only neave that rises from the dorsal end of the brainstem?
the trochlear - also the smallest cranial n.
how does the trochlear nerve get to the orbit?
exits dorsal aspect of brainstem, travels within the lateral wall of the cavernous sinus, enters orbit through superior orbital fissure, and travels along the medial wall of the orbit to innervate the superior oblique m.
Where can the trochlear nerve be found?
running deep to the posterior-most aspect of the superior oblique m.
Where does the opthlamic branch from?
the ICA after it emerges from the cavernous sinus.
how does the ophthalmic a. get into the orbit?
through the optic canal, then branches to supply structures of the orbit
Where is the bulk of the ophthalmic a. found?
between the superior oblique m. and the medial rectus m., and along the medial border of the orbit
What are the smaller branches of the aphthalmic a. and where can they be found?
they accompany their namesake nn. : lacrimal, ant/pos ethmoidal, supr-orbital, supratrochlear, etc.
What centrally located artery does the ophthalmic a. give rise to?
(first branch of the ophthalmic a.) the central artery of the retina, which is bundled with the optic n. (CN II).
how does the central artery get to the retina?
enters the dural sheath of the optic n. (CN II) and travels within the nerve to the retina.
What does the superior ophthalmic v. drain blood from?
eye, superior orbit, ethmoidal cells, forehead, and the angular v. of the face
what does the inferior ophthalmic v. drain blood from?
The inferior ophthalmic v. collects blood from the face and inferior orbit.
What communication of the ophthalmic vv. make it dangerous for spread of infection?
Both the superior and inferior ophthalmic vv. may transport blood from the face to the cavernous sinus.
where are the cavernous sinuses located?
lateral to the sella turcica, extending between the superior orbital fissures (anteriorly) and the apices of the petrous part of the temporal bones (posteriorly)
what veins drain into the cavernous sinus?
ophthalmic vv., sphenoparietal sinuses, and superficial middle cerebral vv
what does the cavernous sinus drain into?
the petrosal sinuses
What structurs traverse through the cavernous sinus?
internal carotid a., abducens n. (CN VI), and internal carotid plexus of sympathetic nn
What nerves are located in the lateral wall (meningeal dura layer) of the cavernous sinus?
oculomotor (CN III), trochlear (CN IV), and the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal n. (CN V)
What nerves can be endangered by cavernous sinus thrombosis?
oculomotor (CN III), trochlear (CN IV), and the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal n. (CN V)
How are the apexes of the cone shaped orbits oriented?
medially
What lines the outside of the optic nerve?
the meningeal dura.
What space is present between the lining of the optic n. and the nerve itself?
subarachnoid space
What coats the posterior eye and mechanisticly supports the eyeball itself?
the bulbar fascia and adipose tissue within the orbit.
As the periostium comes off the bone and extends inferiorly toward the tarsal plate, what is it now called?
the orbital septum (specialization of periostium that attaches periosteal plates to the orbital rim)
what are the 4 anchors of the eyelid?
superior orbital septum
inferior orbital septum
lateral palpebral ligament
medial palpebral ligament
What does the lacrimal caruncle do?
it secretes a sabacious oily substance that lines the conjunctiva and makes the lacrimal fluid flow thorughout the conjunctival space
Which part of the orbicularis oculi is not under your concious control?
the orbital part
what encloses the lacrimal sac?
specialized lacrimal orbicularis oculi fibers (posteriorly) and medial palpebral ligament fibers (anteriorly)
What are the three fiber parts of orbicularis oculi?
orbital, palpebral, and specialized orbicularis oculi fibers behind the lacrimal sac
What fibers does levator palpebral superioris intermingle with anteriorly?
orbital septum
What are the superior tarsal muscle? What is their innervation?
inferior portion of levator palpebrae superioris
BY SYMPATHETIC NERVE FIBERS FROM SUPERIOR CERVICAL GANGLION
CAME UP WITH CAROTID VASCULATURE
What are the innervations of the lacrimal sac?
Afferent: Infratrochlear (V1)
Parasympathetics: Facial n. (CN VII)
Sympathetics: Superior cervical ganglion
What serves the lacrimal apparatus afferently?
the lacrimal n. (V1)
What path does the ophthalmic a. take in the orbit.
It hooks around the optic n. (CN II) from inferior, to lateral, to superior, to medial
What is the only artery in the body that you can see from the outside?
the central artery of the retina
What sympathetic responsibility does the long ciliary serve?
transfers sympathetics from the superior cervical ganglion from ICA to the dialator pupallae
What happens when you constrict your dialator?
It is sympathetically mediated, and they let more light in
Sympathetics let more light in
What happens with intrinsic mm. of the eye when parasympathetics are fired?
When parasympathetic fibers of the eye are fired they constrict and let less light in.
what happens when the oculomotor’s parasympathetics act on the sphincter puppalae and ciliary m. (body)?
Sphincter pupallae constricts to let less light in. Ciliary body relaxes fibers, causes the lens to become more biconvex (see things up close)
what is the common anular tendon also referred to as? what does it encircle?
the common tendinous ring : the optic n., oculomotor n., and abducens n., nasociliary n., and ophthalmic a.
