Orbits I Flashcards
What bones make up the outer rim of the orbit?
The frontal, zygomatic and maxillary bones.
What bones help to form the inside of orbit?
Lacrimal, Ethmoid, Sphenoid and Palatine (in addition to the Frontal, Zygomatic and Maxillary bones which also form the outer rim.)
Palpebral fissure
The space between the upper and lower eye lids. The palpebral margins meet at the canthi (the corner/angle of the eye)
Horner’s syndrome
Lesion to the superior cervical sympathetic ganglion which results in paralysis in the Tarsal muscle on the affected side.
Patient presents with: Ptosis (eye droop), Meiosis (constricted pupil) and Anhydrosis (lack of sweating)
Where is the lacrimal gland located? Where do its ducts drain?
The lacrimal gland is located in the superolateral aspect of the orbit. It’s ducts drain into the superior palpebral fornix.
Where does the lacrimal sac sit?
Anterior lacrimal crest fossa of the maxilla
Where bone is the optic canal associated with?
Its foramen is located in the body of the sphenoid bone.
Where does the levator palpebrae superioris muscle attach?
To the superior tarsus muscle (upper eyelids main component composed of smooth muscle and attaches to the superior tarsal plate). There is also an inferior tarsus muscle.
What muscles help close the upper eyelid?
Transverse running fibers of the Orbicularis oculi, specifically the palpebral portion
What kind of innervation does the tarsus muscle have?
Sympathetic- opens eye very wide.
Lacrimal apparatus
Tears flow inferomedially from the lacrimal gland (superolateral), to the medial canthus, where they drain. Drainage consists of:
Puncta lacrimali (drain opening) Lacrimal canaliculus (duct) Lacrimal sac (collection of fluid) Nasolacrimal duct (drainage to nasal sinus)
How does the lower eyelid move?
It doesn’t. It has no muscles of its own.
Why do we sniffle when we cry?
The more we cry, the more tears are pumped into the nasolacrimal duct into the nasal sinus
Muscles of the orbit (7)
Levator palpebrae superioris (Opens eyelid), SO, SR,MR,LR,IR, IO
Anulus Tendineus
A fibrous ring which encircles the junction of the superior and inferior orbital fissures and the optic canal (optic nerve). This is set up so that the muscles are around the nerve but don’t cross it, thereby preventing pinching of the nerve during contraction.
Innervation of muscles of eye
All are done by CN III (oculomotor) with the exceptions of LR (CN VI) and SO (CN IV)
Function of SR and IR muscles
To pull the eye medially. The orbits are at a 45 degree angle from each other but you want the eyes to look straight. These muscles ensure that.
Which muscles DON’T originate from the annulus tendineus?
Superior oblique, Inferior Oblique, Levator Palpebrae Superioris`
Inferior division of CN III innervates what?
Inferior oblique, inferior rectus, medial rectus and contain parasympathetic fibers which run to the ciliary ganglion from which the short ciliary nerves branch.
What part of CN III innervates the levator palpebrae superioris
Superior branch
Actions of all muscles of the orbit
SR (Elevate and Adducts) IR (Depresses and Adducts) SO (down and out) IO (up and out) MR (adducts) LR (abducts)
Superior division of CN III innervates what?
levator palpebrae superioris and the superior rectus
What hole do the CN III, IV and VI use to enter orbit?
Superior Orbital fissure
What comes through the optic canal?
Optic nerve and Ophthalmic artery
Nerves on the lateral side of the orbit are…
Lacrimal
What nerve starts lateral to optic nerve then crosses over to be medial to it?
Nasociliary nerve
Main nasociliary nerve branches
- Communicating branch (they run through short ciliary nerves but DONT synapse there).
- Long Ciliary
What functions can short ciliary nerves contain? long ciliary nerves?
Short= sympathetic, parasympathetic, general sensory
Long= sympathetic and general only. NO PARASYMPATHETIC
LASSIE
Way to remember the cutaneous branches that come across the eye.
-Lacrimal (LA), Supraorbital (S), Supratrochlear (S), Infratrochlear (I), External Nasal (E)
Main 3 branches of ophthalmic nerve
NFL (nasociliary, frontal, lacrimal)
Where is the frontal nerve located?
Right on top of everything, when you first enter orbit from above
How can you tell short ciliary nerve from long ciliary nerves?
Anything running from the ciliary ganglion to the back of the eye= SHORT CILIARY NERVE
Anything from the nasociliary directly to back of eye= LONG CILIARY NERVE
How do sympathetic fibers enter the orbit for their functions?
They travel from the superior cervical ganglion via the internal carotid plexus and then the ophthalmic division of trigeminal (V1). These fibers pass through the ciliary ganglion and enter the eye via the short ciliary nerves. They also reach the eye via the long ciliary nerves.
Here they innervate the dilator pupillae muscle.
Central retinal
Important artery which runs through the optic nerve.
Venous drainage of the orbit is through the…
Superior and inferior ophthalmic veins, which pass through the superior orbital fissure and enter the cavernous sinus.
True or False?
Both sympathetic and parasympathetic fibers synapse in the ciliary ganglion.
FALSE
Only parasympathetic fibers run through the ciliary ganglion. There are no sympathetic ganglion in the head. The highest is the superior cervical sympathetic ganglion in the neck.
Cell bodies of the post-ganglionic, parasympathetic fibers to the lacrimal gland are found in what ganglion?
The Pterygopalatine Ganglion
The only extraocular muscle which originates from the anterior aspect of the orbit is the…
Inferior Oblique
Is the superior oblique located laterally or medially?
Medially
Inner layer of the eyelid
Palpebral conjunctiva
