anatomy of the orbit and the eye Flashcards
what direction does the apex of the orbit point?
posteriorly
where is the base of the orbit situated?
anteriorly
where is the axis of the eye directed?
anteriorly
where is the axis of the orbit directed?
anteriolaterally
what bones is the roof (superior wall) of the orbit formed by?
frontal bone
sphenoid (lesser wing)
what bones is the floor (inferior wall) of the orbit formed by?
maxilla
palatine
zygomatic
what bones is the medial wall of the orbit formed by?
ethmoid
maxilla
lacrimal
sphenoid
what bones is the lateral wall of the orbit formed by?
zygomatic
sphenoid (greater wing)
what does the optic canal transmit?
optic nerve and ophthalmic artery
what does the superior orbital fissure transmit?
lacrimal, frontal, trochlear, oculomotor, nasociliary and abducens nerves
what vein does the superior orbital fissure carry?
superior ophthalmic
what does the inferior orbital fissure transmit?
zygomatic branch of maxillary nerve
inferior ophthalmic vein
sympathetic nerves
where do orbital rim fractures usually occur?
at sutures joining the 3 bones of orbital rim
what are the 3 bones of the orbital rim?
maxilla
zygomatic
frontal
what is a “blowout” fracture?
partial herniation of the orbital contents through one of its wall
what usually causes “blowout” fractures?
blunt force trauma to the eye
which walls of the bony orbit are the weakest?
medial and inferior
where would the contents herniate into with a blowout fracture?
ethmoid and maxillary sinuses
what are the 3 parts of the orbicularis oculi muscle?
palpebral
lacrimal
orbital
what is the role of the palpebral part?
gently closes eyelid
what is the role of lacrimal part?
involved in the drainage of tears
what is the role of the orbital part?
tightly closes the eyelids
what nerve innervates the orbicularis oculi muscle?
CN VII (facial nerve)
where is the orbicularis oculi muscle located?
deep to skin and connective tissue
where are the tarsal plates located?
deep to palpebral region of the orbicularis oculi muscle
what are the two tarsal plates?
superior (upper eyelid)
inferior (lower eyelid)
what are the tarsal plates composed of?
dense connective tissue
what does the superior tarsus act as?
attachment site of levator palpebrae superioris
what lies in the tarsal plates?
Meibomian glands (tarsal glands)
what does Meibomoian glands secrete?
oily lipid substance that slows evaporation of eye’s tear film and prevents eyelids sticking together when closed
what extends from either tarsus to the orbital margin?
orbital septum
what is the role of the orbital septum?
helps prevent spread of infection between superficial and deep parts of the orbit
what is the role of the levator palpebrae superioris (LPS) muscle?
elevates the upper eyelid
what muscle is LPS attached to?
superior tarsal plate
what does the lacrimal gland produce?
lacrimal fluid
what is the production of lacrimal fluid a result of?
parasympathetic innervation (CN VII)
where does the lacrimal fluid push towards after secretion?
medial angle
once in the medial angle where does the lacrimal fluid drain through?
lacrimal puncta
