UNIT 3: Eyes Flashcards
what are the three axes of movement of the eye?
- vertical: abduction/ adduction
- horizontal: elevation/ depression
- AP axis: medial/ lateral rotation
what nerve innervates the superior rectus and what movements does it produce?
oculomotor - III
elevation/ adduction/ medial rotation
what nerve innervates the inferior rectus and what movements does it produce?
oculomotor - III
depression/ adduction/ lateral rotation
what nerve innervates the medial rectus and what movements does it produce?
oculomotor - III
adduction
what nerve innervates the lateral rectus and what movements does it produce?
abducens - VI
abduction
what nerve innervates the superior oblique and what movements does it produce?
trochlear - IV
depression/ abduction/ medial rotation
what nerve innervates the inferior oblique and what movements does it produce?
oculomotor - III
elevation/ abduction/ lateral rotation
What is the origin of the rectus muscles?
common tendinous ring
what are the origins of the oblique muscles?
superior: body of sphenoid bone
inferior: anterior part of floor of orbit
what movement does the levator palpulae superioris produce and what nerve innervates it?
elevation of upper eyelid (superior tarsal muscle also assists this movement)
innervated by oculomotor nerve has sympathetic and parasympathetic innervations
what is the effect of oculomotor nerve palsy?
paralysis of muscles leads to eyelid droop (ptosis)/ non-reactive pupil/ fully dilated pupil (fully abducted/depressed)
“down and out” presentation
what is the effect of abducens nerve palsy?
paralysis of lateral rectus - eye gaze - eye fully adducted (unopposed pull of medial rectus)
which muscle closes the eyelids and what nerves innervates it?
orbicularis oculi - facial nerve (cranial nerve VII)
where is the lacrimal gland found?
superolateral region of the orbit
give three functions of the lacrimal gland
- lubrication
- nutrition and protection to ocular surface
- contains bactericidal enzymes to fight infection
which nerve gives parasympathetic innervation to lacrimal gland?
facial nerve
which nerve runs over the levator palpebrae superioris in orbit?
frontal nerve - ophthalmic division of trigeminal nerve
describe the visual pathway for left and right visual fields
temporal fibres travel down optic nerve on ipsilateral tracts and synapse at lateral geniculate nucleus and project to primary visual cortex.
nasal fibres travel down optic nerve and DECUSSATE at optic chiasm and travel down tract to synapse onto the lateral geniculate nucleus
describe the visual pathway for upper visual field
fibres in lower retina contain information about upper visual field due to refraction of the cornea. They travel along the optic nerve and tract to synapse onto the lateral geniculate nucleus. the passage of fibres is blocked by the inferior horn of the lateral ventricles so they project around it (aka meyer’s loop) and project onto primary visual cortex inferior to calcarine sulcus
describe the visual pathway for the lower visual field
fibres in the upper retina contain information about the lower visual field due to refraction of the cornea. they travel along the optic nerve and tract to synapse onto the lateral geniculate nucleus. the fibres project directly to primary visual cortex, superior to calcarine sulcus
what region of the brain is the inferior horn of the lateral ventricles and what would be the effect if there was a lesion in this region?
temporal lobe
lesion would cause visual deficit to upper visual field “pie in the sky”
what is the role of the iris and what is its 2 pairs of muscles?
regulate size of pupil aperture - adjustment to light radial dilator - sympathetic innervation (long ciliary) circular constrictor (iris sphincter) -parasympathetic innervation (short ciliary)
describe the lens
held in place by suspensory ligaments attached to ciliary muscle, which has parasympathetic innervation so causes contraction ligaments slacken lens become round - close focussing
what structures form and drain aqueous humour of the eye?
ciliary body: synthesises/ replenishes humour
canal of schlemn - drains humour into bloodstream