Orbit Flashcards
Name the bones that make up the orbit (7)
Frontal
Zygoma
Maxilla
Ethmoid
Lacrimal
Sphenoid
Palatine
What structures pass through supraorbital notch?
supraorbital nerve and artery
What are the eyelids called?
Tarsus
Tarsus contains tarsal gland which releases oily secretions to lubricate eye
What are the ligaments at the medial and lateral aspects of the eye called?
Medial and lateral palpebral ligaments
What ligaments support the eyeball?
Check ligaments - restrict movement of medial and lateral recti
Suspensory ligaments support eyeball in orbit, pass between recti and inferior oblique/rectus
What forms the outer layer of the eyeball?
Cornea and sclera
What forms the vascular middle layer?
Iris, ciliary body, choroid
What is the inner layer of the eyeball?
Retina
contains optic disc, rods and cones
What is the macula lutes?
Fovea of macula
Describe the difference between aqueous and vitreous humor
Aqueous
- Anterior chamber, anterior to lens
- maintains intraocular pressure
- Made by ciliary body and drains into corneo-scleral junction
Vitreous
- Transparent jelly that allows light to pass to retina
- In posterior chamber, posterior to lens
List the intrinsic muscles of the eye
Dilator pupillae
Sphincter pupillae
Cilliary muscle
List the extra-ocular muscles
Lateral rectus Medial rectus Superior rectus Inferior rectus Superior oblique Inferior oblique Levator palpebrae
Describe the features of dilator papillae
Increases diameter of pupil.
Composed of radial fibres.
Sympathetic response = increases light into eye
Describe the features of sphincter papillae
Decreases the diameter of the pupil
protects eye from intense light
composed of circular fibres
Parasympathetic response via CN III
Describe the features of the ciliary muscle
Act to change shape of lens
Allows light to refract as it passes through lens to focus on retina
Relaxed = lens stretched –> distant vision
Contracted = lens relaxed and thick –> near vision
Innervation of the ciliary muscle?
Occulomotor CN III
Describe the innervation of the extra ocular muscles
LR6
SO4
Rest CN III
Pneumonic for actions of extra ocular muscles
RADSIN
Recti Adduct
- except lateral
Superior Intort
What is the route of the optic nerve?
Leaves orbit via optic canal
Forms chiasm over pituitary fossa
Sends optic tracts towards thalamus
Optic radiations carry information to primary visual cortex
How do the other nerves enter the orbit?
Superior orbital fissure.
What nerves pass through cavernous dorsal venous sinus before reaching superior orbital fissure?
CN III, IV, V along walls
CN VI in middle next to internal carotid
Which nerves do not pass through annular ring?
CN VI
Parts of CN V
Branches of CN V1
Frontal = supraorbital and supratrochlear branches
Nasociliary = ant and post ethmoidal
Lacrimal
Which muscles are supplied by superior division of CN III?
Levator palpebre superioris
SR
Which muscles are supplied by inferior division of CN III?
MR
IR
IO
Parasympathetic fibres to intrinsic muscles
What muscle can CN VI be seen on
LR
What can CN IV be seen on?
Surface of SO before piercing and innervationg it
What artery supplies orbit and how does I it enter the orbit?
Ophthalmic (branch of ICA)
Enters through optic canal with optic nerve
What nerve supplies the lacrimal apparatus
secretomotor fibres CN VII carried in CN V1
Lesser petrosal nerve is parasympathetic supply from which nerve?
CN IX
Great petrosal nerve is parasympathetic supply from which nerve?
CN VII
