Lecture 7: Orbit and eye Flashcards
Bones that makeup the bony orbit
-frontal
-sphenoid
-ethmoid
-lacrimal
-Palatine
-Maxilla
-zygomatic
foramen in the bony orbit
-superior orbital fissure
-inferior orbital fissure
-optic canal
3 layers of the eye
outer fibrous layer, middle vascular layer and inner neural layer
wha is the outer fibrous layer composed of
Sclera and cornea
what is the middle vascular composed of
Uvea: Iris, ciliary body, and choroid
what is the inner neural layer composed of
Retina
what colour is sclera
white
Cornea
-first refraction of light entering eye
-directs light to lens
-avascular
Sclera
-supportive outer white layer
-attachment site for extraocular muscles
-covered by mucous membranes (conjunctiva) to lubricate eye
-vascular
Limbus
-transition zone between cornea and sclera
what does the cilairy body do
-produces aqueous humour
-contains siliary muscles
-helps focus lens using zonular fibres and ciliary muscles
Iris
-contains pupillary dilator and sphincter muscles
-controls pupil size depending on light and nervous system signals
Lens
-focuses light on retina
what muscles adjust to things near or far
ciliary muscles
what happens to lens when ciliary muscle is relaxed
zonule fibres tighten, pulling lens flattened for focusing on distant objects
what happens to lens when ciliary muscles contract
zonule relaxes, lens rounded for focusing on close objects and refracting more light
what happens when you view a distant object
- ciliary muscles relax
- Zonular fibres tighten
- lens flattens
what happens when you view a near object
- ciliary muscles contract
- Zonular fibres relax
- lens thickens/rounds
true or false: when viewing near objects, the ciliary muscles contract, which relaxes the zonular fibres and thickens the lens
true
Iris colour is determined by what
colour is determined by amount of melanin
Sphincter Pupillae
-concentric muscle fibres
-constricts pupils when contracted
-PNS (stops light coming in)
DIlator Pupillae
-muscle fibres run longitudinally
towards margins of iris
-enlarges pupil when contracted
-sympathetic NS (helps light in)
what happens to eye when SNS signals sent OR in dim light
dilator pupil contracts
what happens to eye when PNS signals sent OR in bright light
sphincter puppilae contract
Choroid
-nourises retina
-maintains eye temp and volume
Retina
captures light to send to brain
where is the sharpest vision
fovea bc most photoreceptor cells are here
Macula (fovea in center)
most photoreceptor cells here
Optic Disc
-where optic nerve exits the eye (optic nerve is made by retinal axons)
-blind spot -no photoreceptors
Ora Serrata
-anterior border of retina
Optic Nerve
CN II: accumulation of retinal axons
what layer is the sclera and cornea in
outer fibrous layer
what layer is the iris, choroid and ciliary body in
middle vascular layer
what layer is the retina in
inner neural layer
Chambers of the eye
-Anterior Chamber
-Posterior Chamber
-Vitreous chamber
what chambers does the anterior cavity consist of
-anterior chamber
-posterior chamber
what chamber does the posterior cavity consist of
vitreous chamber (largest)
anterior chamber position
posterior to cornea but anterior to iris
posterior chamber position
posterior to iris but anterior to lens
vitreous chamber position
posterior to lens but anterior to retina
what is the anterior chamber filled with
aqueous humour
what is the posterior chamber important for
production and circulation of aqueous humour
aqueous humour purpose
-maintains ocular eye pressure
-replaced every 90 minutes
contents of vitreous chamber
filled with gel-like vitreous humour
purpose of vitreous humour
-maintains eye shape
-nourishes eye
-attached to retina firmly
-makes up about 80% of eye volume
-does not regenerate
which muscle is responsible for opening the eyelid
levator palpebrae superioris
where does the superior oblique sit in the orbit
medially
which extraocular muscle does not originate with the rest
inferior oblique
extraocular muscles
-superior recuts
-lateral recuts
-inferior oblique
-inferior rectus
-medial rectus
-superior oblique
-levator palpebrae superioris
what does the superior oblique wrap through
the trochlea
what CN enter the eye orbit
trochlear, abduces, optic and oculomotor
which way does the superior rectus pull the eye
up
which way does the lateral rectus pull the eye
rolls eye laterally
which way does the inferior oblique pull the eye
up and out
which way does the inferior rectus pull the eye
rolls eye down
which way does the medial rectus pull the eye
rolls eye medially
which way does the superior oblique pull the eye
down and out
WHich muscles are innervated by the oculomotor nerve
medial rectus, superior rectus, inferior oblique, and inferior rectus
which muscles are NOT innervated by the oculomotor nerve
-Lateral rectus (abducens)
-Superior Oblique (trochlear)
Lacrimal Apparatus
-system of glands and ducts
-produces and drains lacrimal fluid
lacrimal fluid
-lubricates eye surface
-removes debris from eye
-amount 1mL produced each day
path of lacrimal apparatus
- Lacrimal gland
- Excretory lacrimal ducts
- superior and inferior puncta (via blinking)
- Superior and inferior lacrimal canaliculi
- Lacrimal Sac
- Nasolacrimal duct
