Orbit I Flashcards
What three bones make up the outer rim of the orbit?
Which bones help form the inside of the orbit?
base medial wall apex roof lateral wall
frontal, zygomatic, maxillary
Lacrimal, ethmoid, greater and lesser wings of sphenoid, palatine
base- orbital margin
medial wall- ethmoid, lacrimal, frontal, palatine, maxilla
apex- optic canal
roof- frontal; sphenoid
lateral wall- zygomatic and sphenoid, maxilla, frontal
What controls the eyelids?
What is the palpebral fissure?
Where do palpebral margins meet?
palebrae
space between upper and lower lids, bounded by the upper and lower palpebral margins
margins meet at canthi (angles)
What might cause Horner’s syndrome?
What would be the clinical manifestations?
Lesion to the superior cervical sympathetic ganglion, with resulting paralysis in Tarsal muscle on the affected side.
Ptosis (drooping eyelid)
Meiosis (small pupil)
Anhydrosis (lack of sweating
Where is the lacrimal gland located?
Where does its ducts drain?
Are the motor fibers to lacrimal gland para/symp?
superolateral aspect of the orbit.
It’s ducts drain into the superior palpebral fornix (located at the junction of the palpebral and orbital conjunctiva).
motor fibers to lacrimal gland are parasympathetic in nature
Where do tears flow from?
Where do they drain? (4 places)
Tears flow from the superolaterally placed lacrimal gland, inferomedially to the medial canthus of the eye, where they drain:
Puncta lacrimali – drain opening
Lacrimal canaliculus - duct
Lacrimal sac – collection of fluid
Nasolacrimal duct – drainage to nasal sinus
Describe the innervation of the lacrimal gland.
greater petrosal nerve (through internal auditory meatus) deep petrosal nerve nerve of pterygoid canal maxillary nerve (CN V2) lacrimal nerve (CN V1) pterygopalatine ganglion
What are the extraocular muscles?
Which 4 insert on the median plane of eye?
muscles of the orbit: superior oblique, levator palpebrae superioris, superior rectus, medial rectus, lateral rectus, inferior rectus
4 rectus insert on median plane of eye
Where do the muscles of the orbit (recti muscles) originate?
anulus tendineus, a fibrous ring which encircles the junction of the superior and inferior orbital fissures and the optic canal (optic nerve).
Which muscles do not originate from anulus tendineus? Where do they originate?
superior oblique- sphenoid
inferior oblique- maxilla
levator palpebrae superioris- sphenoid
How is the orbit directed from posterior to anterior?
orbit is directed in a medial to lateral direction. This explains the medial pull of the superior and inferior rectus muscles
What is the action of the medial and lateral rectus on their horizontal axis?
medial rectus- adducts
lateral rectus- abducts
Which muscles would you engage if you wanted to look right?
your right lateral rectus and your left medial rectus
What is the largest nerve in the orbit?
What does it do?
optic nerve
conveys sensory information (vision) from retina to CNS
Which nerve crosses above the optic nerve from lateral to medial? What important branch does it give off?
nasociliary nerve (of CN V1)
communicating branch to the ciliary ganglion: runs through ciliary ganglion (without synapsing), then reaches the eye by running through the short ciliary nerves
gives off long ciliary nerves
What type of fibers run through the ciliary ganglion without synapsing in it?
Which type of fibers synapse in the ciliary ganglion.
What do short ciliary nerves do?
Sensory and sympathetic fibers run through this ganglion without synapsing in it.
Parasympathetic fibers from the oculomotor nerve (CN III) also reach the ganglion and are THE ONLY MODALITY OF FIBERS WHICH SYNAPSE IN THE CILIARY GANGLION.
The short ciliary nerves (several in number) connect the ciliary ganglion to the posterior aspect of the eye.
