Week 1 - A - Anatomy of the orbit and eye Flashcards
What bone forms the inferolateral margin of the orbital?
The zygomatic bone
What bone forms the superior margin of the orbit?
The frontal bone
What bone forms the inferiormedial margin of the orbit?
The maxillary bone
From medial t lateral state the bones So the: blue, yellow then pink
Blue bone - lacrimal bone Yellow - ehtmoid bone Pink - sphenoid bone
What is the hole in sphenoid bone? - lying immediately lateral to the ethmoid bone
This is for the optic canal
The ethmoid air cells (sinus) lie behind the ethmoid bone, where does the ethmoid sinus drain? (remember the ethmoid air cells have a posterior, anterior and middle)
Posterior ethmoidal air cells - superior meatus Anterior ethmoidal air cells - semilunar hiatus of middle meatus Middle ethmoidal air cells - ethmoidal bulla of middle meatus
thin, semitransparent mucous membrane that covers the posterior surface of the eyelids and is then reflected onto the eyeball
This is the conjuctivae It is non-keratinized stratified columnar epithelium with goblet cells
What is the foramina just below the orbit in the maxillary bone? What nerve passes through here that provides sensory innervation to the skin of the lower eyelid, side of the nose, moveable part of nasal septum, anterior cheek and upper lip?
The infra-orbital foramen The ifra-orbital branch of the maxillary division of the trigeminal nerve passes through here
The eyelids contain glands which secrete an oily substance to stop the evaporation of tears What is this substance known as
Meibum Produced by the tarsal glands (aka the meibomian glands)
The arrows pointing towards the yellw and green in the middle of the picture are what?
Pointing towards yellow - the tarsal gland (meibomian gland) produces meibum Pointing towards green - tarsal plate
What is the function of the tarsal plate?
Contributes towards support of the eyelid
What muscles are responsible for the movements of the eyeball and superior eyelid?
The extra-ocular muscles
What muscles causes elevation of the upper eyelid?
The levator palpabrae superioris
What is the concentric muscle of facial expression? (supplied by CN VII) What is its function?
The orbicularis oculi Closes the eylid when contracting and sweeps tears across the eyeball and on its way to drainage via the punctum
What glands produce tears? Where are they situated?
Lacrimal gland - situated int he superiolateral region of the orbit
What is the function of tears?
Tears lubricate the eyes and capture dirt and then drain them into the nasal cavity
After tears are produced and travel across the cornea (helped by orbicularis oculi moving the eyelid), how do they travel to the nasolacrimal duct?
Tears are produced by lacrimal gland then go to - cornea - then through the lacrimal punctum to the lacrimal canaliculi (superior and inferior) - the lacrima canaliculi connects to the lacrimal sac which connects to the nasolacrimal duct
Where does the nasolacrimal duct drain?
Drains into the inferior meatus on the lateral wall of the nasal cavity
What nerve supplies the lacrimal gland?
The greater petrosal nerve - branch of the facial nerve (CN VII)
Are glands usually supplied by sympathetic or parasympathetic? What are the parasympathetic cranial nerves?
Usually by parasympathetic apart from the sweat glands which are sympathetic CN III - oculomotor nerve CN VII - facial nerve CN IX - glossopharngeal nerve CN X - vagus nerve
What membrane covers the cornea and the sclera of the eyeball? Mucous membrane
The conjunctivae - non-keratinized stratified columnar epithelium with goblet cells
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The conjunctivae Diagnosis For A - allergic conjunctivitis For B - infective conjunctivitis Pus makes B likley to be infective (probably bacterial)
What are the three layers of the eyeball? What composes the layers?
Outer fibrous layer - sclera with cornea in middle Middle vascular layer - choroid (uvea), ciliary body, iris Inner layer (nervous and pigmented) - retina
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1 - cornea 2 - anterior chamber 3 - pupil 4 - iris 5 - sclera 6.Suspensory ligaments of the lensv(posterior camber found between the iris and suspensory ligaments of the lens) 7 - lens 8- ciliary muscles 9 - sclera
Where do the extra-ocular muscles attach? Makes up 85% of the fibrous layer of the eye
The sclera comprises the majority of the fibrous layer (approximately 85%). This is where the extra-ocular muscles attach
What is the transparent layer at the front of the eye?
The cornea
The vascular layer of the eye lies underneath the fibrous layer What does it consist of?
Consists of the choroid , the ciliary body (containing the muscles) and the iris
What attaches the ciliary muscles to the lens of the eye?
Zonular fibres attach the ciliary body to the lens Zonular fibres also known as suspensory ligament of the lens
What happens to the shape of the lens when the ciliary muscles contract? What is this process known as?
When the ciliary muscles contract, the suspensory ligaments relax allowing the lens to widen - near vision When the ciliary muscles relax, the suspensory ligaments become taught causing the lens to flatter (distant vision)
What is situated between the lens and cornea with a gap for the pupil in the middle?
The iris
Smooth muscle fibres of the iris cause constriction of the pupil What provides parasympathetic innervation to the iris cons
The parasympathetic fibres of the oculomotor nerve (CN III)
When do the constrictor muscle of the pupil work?
Works in bright light as not as much light is needed to enter the eye
What is the muscle of the iris under sympathetic control that is used to dilate the pupil in dim light?
The dilator pupillae of the iris
What is the area of most distinct vision of the eye?
The fovea of the eye - located in the macula
What are the six extra-ocular muscles?
Superior oblique - attaches to lateral upper side of the eye
Inferior oblique - attaches to lateral underside of eye
Superior rectus
Middle rectus
Lateral rectus
Inferior rectus
Where do the extra-ocular rectus muscles of the eye move the eye?
Superior rectus - moves eye superiorly and medially (up and in) Inferior rectus - moves eye inferiorly and medially (down and in) Lateral rectus - abducts eye Medial rectus - adducts eye
Where do the superior oblique and inferior oblique muscles move the eye?
Superior oblique moves eye inferiorly and laterally (down and out) (remember tramp is down and out) Inferiorly oblique moves eye superiorluy and laterally (up and out)
What does the superior oblique pass through (pully) and what is its nerve supply?
Passes through the trochlea and is supplied by the trochlear nerve
What does the lateral rectus cause and what supplies it?
Causes abduction (lateral) of the eyeball Supplied by CN VI - abducent nerve
What is the nerve supply of all 6 extra occular nerves? What is the nerve supply of the levator palpabrae superioris?
* Superior, medial and inferior rectus + Inferior oblique - oculomotor nerve * * Superior oblique muscle - trochlear nerve (causes eye to move down and out) (inferolaterally) * Lateral rectus - abducent nerve (causes abduction(lateral movement) Levator palpabrae superioris supplied by CNIII (oculomotor nerve)
Clinical testing of the eye slightly differs from the normal movements of the eye Explain how you would test each of the obliques
Testing Superior oblique muscle - ask patient to move eye medially and then inferiorly (ends up with down and in) Inferior oblique muscle - as patient to move eye medially and then superiorly (up and in)
When testing the obliques, the superior oblique is located on the superolateral aspect of the eye - therefore moving the eye medially can isolate the superior oblique if you then move the eye downwards What surface of the eye is the inferior oblique located on? how is it tested?
Located on inferolateral surface so once moving the eye medially, contracting of the inferior oblique will cause the eye to go upwards
What direction do you ask the patient to test the eye for the lateral and medial rectus?
For lateral - laterally For medial - medially
What movememnt for superior and inferior rectus?
For superior -ask patient to move eye laterally and the superiorly (up and out) For inferior rectus - ask patient to move eye laterally and inferiorly (down and out)
60 year old patient attends your opthamology for evaluation of his ptsosis Which affected muscle is most likely to be the cause?
Ptosis, also known as blepharoptosis, is a drooping or falling of the upper eyelid Muscle cause is levator palpabrae superioris
22 year old has been punched upper right cheek Indicaticates a inferiorlateral fracture Which bone?
Inferolateral fracture of orbit is zygomatic bone
Would like to test CN IV – following movements of your finger, which directions hould the eye move to best test the function?
Testing the superior oblique muscle of the eye Ask patient to move eye medially and then inferiorly (So down and in)
Eye lid has dropped, eye ball is slightly depressed and abducted (down and out) Which nerve is damaged?
As the supeiro oblique eye movement is unopposed it is working Therefore it is oculomotor
State the normal movements of the superior oblique muscle and state how to test? Do the same for the inferior oblique?
Superior oblique normal movement - moves eye down and out (inferolaterally) * Testing - move eye medially then inferiorly, (down and in) Inferior oblique normal movement - moves eye up and out (superolaterally) * Testing - move eye medially then supiorly
Name the two muscles that depress the eye and the two muscles that elevate the eye?
Inferior rectus Superior oblique These two muscles depress the eye Inferior oblique Superior rectus These two muscles elevate the eye
