Orbit Flashcards
ID the structure:
Resembles a 4-sided pyramid with the base anteriorly and apex posteriorly.
Bony orbit
10% of all facial fractures are isolated ________ fractures.
Orbital wall
___________ % of all fractures involve the orbit.
30-40%
Bony Orbit superior boundary:
Anterior cranial fossa
Bony Orbit inferior boundary:
Maxillary sinus
Bony Orbit ______ boundary:
Nasal cavity
Medial
Lateral boundary of bony orbit:
Middle cranial fossa and temporal fossa
Sphenoid sinus and middle cranial fossa are ____ boundary of the bony orbit.
Posterior
What CNs pass through the orbit?
CN II III IV V1 VI
Name the contents of the orbit:
- Orbital fat
- EOMS
- Globe
- CN II III IV V1 VI
- Lacrimal apparatus
- Arteries and veins
Name the parts of the lacrimal apparatus:
- Lacrimal gland
- Lacrimal sac
Name the paired bones of the orbit:
- Lacrimal
- Palatine
- Zygomatic
- Maxillary
Name the unpaired bones of the orbit:
- Ethmoid
- Frontal
- Sphenoid
bony orbit is composed of ____ bones.
7
Name the openings into the orbit:
- Superior orbital fissure
- Inferior orbital fissure
- Optic canal
Superior orbital fissure is an opening between ______ and _____.
Greater and lesser wings of sphenoid
Name the opening between greater wing of sphenoid and maxilla.
Inferior orbital fissure
This opening lies between lesser wing and body of sphenoid, at the orbital apex.
Optic canal
Which opening is at the orbital apex of the eye?
Optic canal
The roof of the orbit underlies:
frontal sinus and anterior cranial fossa
The roof of the orbit is formed by:
Orbital plate of frontal bone
Lesser wing of sphenoid
Orbital plate is a thick and sturdy bone. (T/F)
False: it’s a very thin bone.
Roof is thinnest at ______.
areas of frontal sinus
Orbital roof anamoly/fracture is typically due to:
Significant head trauma
Unhelmeted motorcycle accidents are examples of __________ fractures.
Orbital roof
Possible sequelae of the orbital roof:
- CSF rinorrhea
- Orbital encephalocele
What is orbital encephalocele?
Protrusion of brain through skull defect
The floor of the orbit is composed of:
- Orbital plate of maxillary bone
- Orbital plate of zygomatic bone
- Orbital process of palatine bone
Medial wall of the orbit is composed of:
- Frontal process of maxilla
- Lacrimal bone
- Orbital plate of ethmoid bone
- Body of sphenoid bone
Anterior + posterior lacrimal crests:
Lacrimal fossa
How can one get an orbital medial wall fracture?
The medial wall is extremely thin.
Prone to damage and sinusitis spread of infection.
May lead to orbital cellulitis
What can lead to orbital cellulitis?
Fracture/anamoly of the orbital medial wall.
Strongest and the thickest wall of the orbit is:
The lateral wall
These bones make the ______ wall of the orbit.
- Frontal process of maxilla
- Lacrimal bone
- Orbital plate of ethmoid bone
- Body of sphenoid bone
Medial
The lateral wall of orbit is composed of:
- Zygomatic bone
- Greater wing of sphenoid
- Zygomatic process of frontal bone
This bone separates orbit from temporal fossa.
Zygomatic bone
This bone separates orbit from middle cranial fossa.
Greater wing of sphenoid
Define periorbita:
All bones are lined with periorbita, which is a dense layer of vascular CT.
Periorbita is continuous at __________ and __________ with periosteal layer of dura.
Optic canal; superior orbital fissure
Choose on:
Periorbita is loosely/firmly attached to the orbital bone.
Loosley
Periorbita is firmly attached to:
- Trochlea
- Optic canal
- Orbital fissures
What is trochlea and it’s function?
Cartilaginous pulley structure for the superior oblique muscle
Define orbital septum:
Dense CT, extension of periobita into eyelids.
Orbital septum runs from ______ to ______.
Entire orbital rim to tarsal plates of eyelids
What is the fxn of the orbital septum?
- Barrier to spread of infection from eyelids into orbit
- Restricts fat from falling onto the lid margins
This CT system is posterior to lacrimal sac:
Orbital septum
ID the structure:
Runs from entire orbital rim to tarsal plates of eyelids
Orbital septum
Common Tendinous Ring aka
Annulus of Zinn
Common tendinous ring is passage for:
- Nasociliary nerve (V1)
- Oculomotor nerve (superior & inferior divisions)
- Abducens nerve
- Optic nerve
- Ophthalmic artery
Tenon’s capsule is made of:
Dense elastic CT
ID the structure:
Lies between conjunctiva and episclera and merges with both at the limbus
Tenon’s capsule
Tenon’s capsule fuses with ___________ posteriorly.
Optic nerve sheath
What is the name of the structure that serves as a protective cover over EOM’s where they insert into the sclera?
Tenon’s capsule
What separates globe from orbital fat?
Tenon’s capsule
Tenon’s capsule functions:
- separates globe from orbital fat
- serves as a protective cover over EOM’s where they insert into the sclera
Name the voluntary muscles of the orbit:
- 4 recti
- 2 oblique
- lavator palpebrae superioris
lavator palpebrae superioris fxn:
elevates eyelid
_______ muscles allow for movement of globe within the orbit.
Extraocular
Involuntary muscle of the orbit:
Muller’s muscle
Which muscle originates on the LPS and extends into the tarsal plates?
Muller’s muscle
Muscle action
Lateral rectus
Abduction
Muscle for adduction
Medial rectus
Muscle for elevation, adduction, intorsion.
Superior rectus
Muscle for depression, adduction, extorsion
Inferior rectus
Muscle action
Superior oblique
Intorsion, depression, abduction
Muscle for extorsion, elevation, abduction
Inferior oblique
Field of action of each muscle is _____.
The direction where particular muscle has the greatest action
In lateral gaze, __________ is negated.
medial pull of SR/IR
In ____ gaze, lateral pull of SO/IO is negated.
Medial
Lavator palpebrae superioris origin and insertion
Origin: lesser wing of sphenoid bone
Insertion: superior tarsal plate and skin of eyelid
Elevation of eyelid is the primary action of this muscle.
Lavator palpebrae superioris
Primary action of superior rectus:
Elevation of globe
These muscles originate at common tendinous ring and insert into sclera.
superior rectus
medial rectus
inferior rectus
lateral rectus
Depression of the globe is done by ______.
Inferior rectus
Origin and insertion of inferior rectus:
Origin: common tendinous ring
Insertion: sclera
Primary action of lateral rectus:
Abduction of globe
Primary action of ________ is to adduct the globe.
Medial Rectus
Primary action of superior oblique:
Intorsion of globe
superior oblique inserts into:
sclera
This muscle originates from body of sphenoid above common tendinous ring:
superior oblique
Extorsion of globe is done by:
Inferior oblique
Inferior oblique origin and insertion:
Origin: orbital surface of maxilla
Insertion: sclera
All recti and oblique muscles insert into:
Sclera
These two muscle are innervated by superior division of CN III.
- Lavator palpebrae superioris
- Superior rectus
IR and MR are innervated by:
Inferior division of CN III
This muscle is innervated by CN IV:
Superior oblique
These muscles are innervated by inferior division of CN III:
- Inferior rectus
- Medial rectus
- Inferior oblique
- VE to ciliary ganglion
CN VI innervates this muscle:
Lateral rectus
Secondary action of this muscle depression:
Superior oblique
Secondary action of inferior oblique:
Elevation
Adduction is the secondary action of:
Inferior rectus
Superior rectus
Motor innervation of the orbit is via these CNs:
III (superior and inferior divisions), IV, VI
Sensory information of the orbit is via these CNs:
CN II and V1
Orbital blood supply is via:
Ophthalmic artery
venous drainage of the orbit is via:
- Superior ophthalmic vein
- Inferior ophthalmic vein
- Cavernous sinus
Location of superior ophthalmic vein:
Junction of supra-orbital and angular veins
Superior ophthalmic vein drains into:
Cavernous sinus
Drains into cavernous sinus or pterygoid venous plexus via IOF:
Inferior ophthalmic vein
Drains most of the ocular structures:
Cavernous sinus
What’s in the ridge of superior orbital margin?
- 2 mm posterior to lateral margin: lacrimal gland fossa
- 2 mm posterior to medial margin: trochlea
Floor of the orbit is separated from the lateral wall by:
Inferior orbital fissure
This part of the orbit connects the pterygopalatine fossa to the face:
Floor of the orbit
The floor of the orbit contains infraobrital canal that opens onto the face via the ___________ in order to transmit ____.
Infraorbital foramen; V2
The bone that is most likely to be fractured at the floor of the orbit is:
The maxillary bone
Orbital floor fracture can lead to:
- Prolapsed orbital fat in the maxillary sinus
- Damage to the infraorbital nerve
- IR muscle entrapment
Damage to the infraorbital nerve can result in:
loss of GA sensation from the cheek area of the face
Lamina papyracea means _______ and is another name for _________.
Paper thin; orbital plate of the ethmoid bone
Fossa for lacrimal sac medially is made by groove within _____________ and ____________.
lacrimal bone and frontal process of maxilla
Lacrimal fossa continues as _______________ to drain into the _______________.
nasolacrimal canal; inferior nasal meatus
______ wall fractures of the orbit normally don’t need a repair.
Medial
Common tendinous ring is anterior/posterior to optic canal. Choose one.
Anterior
All recti muscles originate from:
Common tendinous ring
T/F:
Both divisions of the occulomotor nerve pass through the common tendinous ring.
True
T/F:
CN IV Trochlear nerve passes through the Common tendinous ring.
False. Passes through the superior orbital fissure
If angles of gaze and muscle coincide at 23*, elevation is done by:
Superior rectus
If angles of gaze and muscle coincide at 23*, ________ in done by Inferior rectus.
Depression
If angles of gaze and muscle coincide at 51*, ________ muscle will depress the eye.
Superior oblique
If angles of gaze and muscle coincide at 51*, _____________ is done by inferior oblique.
Elevation
Antagonist to superior rectus is:
Inferior rectus
Sensory innervation of the orbit is via these CNs:
- CN II
- CN V1
Sensory afferent information responsible for vision is carries by:
CN II
General afferent from orbit, upper eyelid, superior face and forehead are carries by this CN:
CN V1
CN II is responsible for _____.
Vision (SA)
Choose one:
CN V1 divides into 3 before/after entering the orbit.
Before
Frontal and lacrimal divisions of CN V1 enter the orbit via _______, ______ the tendinous ring.
SOF; above
______ division of CN V1 enters the orbit via SOF and passes through the common tendinous ring.
Nasociliary
Frontal divison of CN V1 farther divides into:
- supratrochlear
2. supraorbital
Arterial supply to retina is via:
CRA: central retinal artery
Arterial supply by lacrimal artery is to:
- lacrimal gland
- conjunctiva
- eyelid
Short posterior ciliary arteries supply blood to:
choroid
Ciliary body and the iris are supplied by:
Long posterior ciliary arteries
Muscular branches supply:
-EOMs
Anterior ciliary artery branches off of ________ and supplies the _______.
Muscular branches; Iris
Eyebrows, forehead and the scalp are supplied by:
Supraorbital artery
Supratrochlear artery supplies:
Forehead and scalp
Anterior ethmoid artery supplies:
- Ethmoidal air cells
- frontal sinus
- nasal cavity
- external nose
Upper and lower eyelid arches are supplied by:
Medial palpebral artery
Side of the nose and lacrimal sac are supplied by:
Dorsal nasal artery
