Lecture 7 - Orbit and Eye Flashcards
what is the bony orbit?
- bilateral, symetrical cavities containing the eyballs and associated structures
What bones/fractions of bones can be found in the bony orbit?
- frontal bone
- sphenoid bone
- ethmoid bone
- lacrimal bone
- palatine bone
- maxilla
- zygomatic bone
What fissures/canals are in the bony orbit?
- superior orbital fissure
- inferior orbital fissure
- optic canal
What nerves pass through the superior orbital fissure?
- occulomtor nerve (CNIII)
- trochlear nerve (CN IV)
- ophthalmic divison of trigemincal nerve (CN V1)
- abducens nerve (CN VI)
What nerve passes through the optic canal
- optic canal (CN II)
What are the three layers of the eye? (from deep to superficial)
- inner neural layer (retina)
- middle vascular layer
- outer fibrous layer
What structures are within the outer fibrous layer?
- sclera
- cornea
- limbus
Cornea
- first refraction of light entering eye
- directs light to lens
- avascular
Sclera
- suppoetive 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 structures are within the middle vascular layer?
uvea:
- iris
- cilliary body
- choroid
- lens
- zonular fibers
Iris
- contains pupillary dilator and sphincter muscles
- controls pupil size depending on light and NS signals
Ciliary body
- produces aqueous humour
- contains ciliary muscles
- helps focus lens using zonular fibers and ciliary muscles
lens
- focuses light on retina
What are the three muscles in the middle vascular layer?
- intraocular muscles
-extraocular muscles - ciliary muscles
- pupillary muscles
Intraocular vs extraocular muscles
- intra = within the eye
- extra = outside the eye
Ciliary muscles
contracts and relax to change lens so you can see close/far
- when looking far away, muscles contract
Pupillary muscles (3)
- iris
- sphincter pupillae
- dilator pupillae
Sphincter pupillae
- concentric muscle fibers
- construct pupil when contracted
- parasympathetic NS
Dilator pupillae
- muscle fibers run longitudinally towards margins of iris
- enlarges pupils when contracted
- sympathetic NS
Pupil size when bright light or PSNS signals
small
Pupil size when dim light or SNS signals
large
Middle vascular layer - choroid
- nourishes retina
- maintains eye temp and volume
Inner neural layer
retina
Retina
- macula (fovea in centre)
- optic disc
- ora serrata
- optic nerve
macula (fovea in centre)
- highest concentration of photoreceptor cells
- rods and cones
optic disc
- where opti nerve exits the eye (optic nerve is made by retinal axons)
- blind spot - no photoreceptors
ora serrata
anterior border of retina
optic nerve
accumulation of retinal axons
Myopia
- near-sightedness
- lens or eyeball is too long
- image is focused in front of fovea
Hyperopia
- far-sightedness
- lens or eyeball is too short/flat
- image is focused behind fovea
Chambers of the eye
- anterior chamber
- posterior chamber
- vitreous chamber
Which chambers are part of the anterior cavity?
- anterior chamber
- posterior chamber
Which chambers are part of the posterior cavity?
- vitreous chamber
Anterior chamber
- between cornea and iris
- filled with aqueous humor (maintains ocular pressure, replaced every 90 minutes)
Posterior chamber
- between iris and lens
- important for production and circulation of aqueous humour
Vitreous chamber
- filled with gel-like vitreous humour
Vitreous humour
- maintains shape of eye
- nourishes eye
- attached to retina
- makes up about 80% of eye volume
- does not regenerate
Extraocular muscles (8)
- trochlea
- superior oblique
- superior rectus
- medial rectus
- lateral rectus
- inferior rectus
- inferior oblique
- levator palebrae superioris
Movements of eye: superior oblique
down and out
Movements of eye: inferior oblique
up and out
What nerve innervates the extraocular muscles? With the exception of two of the muscles with are the…?
- the oculomotor nerve (CN III)
- except for Superior Oblique and Lateral Rectus (SO-LAR)
What nerve innervates the superior oblique?
- trochlear nerve (CN IV)
- trochleae = “pulley” = pulls eye
What nerve innervates the Lateral Rectus?
abducencs nerve (CN VI)
- abducens abdcuts eye
What is the lacrimal apparatus?
system of glands and ducts
- produces and drains lacrimal fluid (tears)
What do lacrimal fluid (tears) do?
- lubricate eye surface
- removes debris from eye
- about 1 mL produced each day
lacrimal apparatus components/structures
- lacrimal gland
- excretory lacrimal ducts
- superior and inferior puncta
- superior and inferior lacrimal canaliculi
- lacrimal sac
- nasolacrimal duct
