Anatomy of the eye and orbit (orbit) Flashcards
Name the 6/7 bones which make up the orbit
frontal, maxillary, zygomatic, lacrimal, ethmoid, sphenoid and (palatine)
3 foramen in the orbit
optic foramen
superior orbital fissure
inferior orbital fissure
What fissure separates the greater and lesser wings of the sphenoid?
superior orbital fissure
What is so important about these 3 foramina in the apex of the orbit?
all neurovascular structures to the orbit must make their way via one of these
What makes the medial and inferior orbital walls particularly weak?
closely related to air sinuses
3 air sinuses closely related to the orbit
frontal, maxillary and ethmoidal air cells
Compare the length of they eyeball and the orbit and what is found in the space?
eyeball is much shorter than the orbit
orbital fat
function of orbital fat
cushions globe and support
Difference between lids and conjunctiva
lids - skin on outside
conjunctiva - mucous membrane on inside
What glands are found in eyelashes which can cause sty’s?
sebaceous glands
What muscle a) elevates the eyelid and b) closes the eyelid?
a - levator palpebrae superioris
b - orbicularis occui
What is the tarsal plate and its function?
hard plate deep to the orbicularis occuli to keep shape
Glands found inside the tarsal plate
meibomian glands
What are meibomian glands function?
oily secretory glands for the tear film
Conjuctiva
mucous membrane - thin and vascular
covers the inner surface of the eyelids and the sclera
Why does the conjunctiva not cover the cornea?
blood vessels often leak and do not want these sitting on top of a transparent cornea
Where is the lacrimal gland situated?
superior laterally of the orbit
Parasympathetic innervation of the lacrimal gland
facial nerve
What does the lacrimal duct open onto?
conjunctival sac
How are the tears spread over the cornea?
each blink evenly coats the cornea after the conjunctiva has been coated
punctae
tiny hole in the medial part of the eyelid
tear drainage pathway
tear –> punctae –> lacrimal sac –> nasolacrimal duct–> inferior meatus
What bone does the lacrimal sac lie over?
lacrimal
When the orbicularis occuli contracts what happens to the tears?
the lacrimal sac is opened and the tears are sucked in
Intrinsic ocular muscles found where?
iris and ciliary body
Intrinsic ocular muscles - the 2 functions
control the size of the pupil
alter the curvature of the lens to see objects close up
Extrinsic ocular muscles - main function
move the eye
Difference in intrinsic and extrinsic muscles origin and attachment
extrinsic - start in orbit and end on sclera
intrinsic - start and end in the eyeball
3 intrinsic eye muscles
ciliaris muscle
constrictor pupillae
dilatory pupillae
Of the 2 pupillae muscles which is circular and which is radially arranged?
constrictor = circular dilator = radial
innervation of the 3 intrinsic muscles
ciliaris and constrictor = parasympathetic by oculomotor nerve - CN 3
dilator - sympathetic by nerve plexus around blood vessels
Name the 6 extrinsic ocular muscles
rectus - medial, lateral, superior, inferior
oblique - inferior and superior
Which muscle has a trochlear?
superior oblique
Which muscle arises from the anterior aspect of the orbit?
inferior oblique
What do the 4 recti muscles arise from?
posterior apex from an annular fibrous ring
What muscles attach to the sclera anteriorly and which posteriorly?
recti = anterior oblique = posterior
What muscle lies just above the superior rectus?
LPS
Where does the LPS attach?
upper eyelid
What muscle does the trochlear nerve innervate?
superior oblique - Think Trochlear
What muscle does the abducent nerve innervate?
muscle which abducts the eye eg moves it away from the nose which is the LATERAL RECTUS
What is the main nerve supply for the enxtrinsic ocular muscles?
oculomotor nerve
What 4 cranial nerves are in the orbit?
2,3,4,6
What foramen does the optic nerve travel?
optic foramen
What does the optic nerve carry?
special sensory fibres
What muscle innervates the LPS?
oculomotor nerve
Where do the parasympathetic fibres of the oculomotor nerve synapse?
ciliary ganglion in the orbit
Where does the trochlear nerve arise?
dorsal part of the midbrain
