Anatomy of the Eyeball and Visual Pathways Flashcards
Orbit and the Eye:
Where is the bony orbit located?
How many bones does the bony orbit comprise of?
- viscerocranium
- 7 bones
Bony Orbit: Location:
- anterior cranial fossa
- maxillary paranasal air sinuses
- nasal cavity
- middle cranial fossa
- zygomatic process, zygomatic
bone
- Anterior cranial fossa = superiorly
- Maxillary paranasal air sinuses =
inferiorly - Nasal cavity = inferomedially
- Middle cranial fossa = posteriorly
- Zygomatic process of maxilla,
zygomatic bone = laterally
Content of the Bony Orbit:
- eyeball
- optic nerve
- extra-ocular muscles
- lacrimal apparatus
- neurovascular structures
- periorbital fat and fascia
Bony Orbit:
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Bony Orbit:
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What bones make up the roof of the orbit?
- orbital part of the frontal bone
- lesser wing of sphenoid bone
What bones make up the medial wall of the bony orbit?
- frontal process of maxilla
- lacrimal bone
- ethmoid bone
- sphenoid bone
Where are the lacrimal and trochlear fossa located on the bony orbit?
- lacrimal fossa = lateral part of roof
- trochlear fossa = medial part of
roof
Where are the following foramina located on the bony orbit?
- anterior and posterior ethmoidal
foramina - optic canal
- superior part of medial wall
- middle part (inferior to ethmoidal
foramina) of medial wall
What passes through the anteiror and posterior ethmoidal foramina?
ethmoidal vessels and nerves
What passes through the optic canal?
- optic nerve
- ophthalmic artery
What bones make up the floor of the orbit?
- orbital surface of maxilla
- zygomatic bone
- palatine bone
What bones make up the lateral wall of the orbit?
- zygomatic bone
- greater wing of sphenoid
Where are the following foramina located in the bony orbit?
- inferior orbital fissure
- superior orbital fissure
- inferior orbital fissure = lateral
border of the floor - superior orbital fissure = superior
border of lateral wall
What passes through the inferior orbital fissure?
- CNV5 = maxillary division of
trigeminal - infra-orbital vessels
- inferior ophthalmic vein
What passes through the superior orbital fissure?
- CNIII = occulomotor
- CNIV = trochlear
- CNVI = abducen s
- CNV1 (ophthalmic nerve branch of
trigeminals) branches lacrimal,
frontal and nasocilliary - superior ophthalmic vein
Bony Orbit:
in lateral zygomatic is blue, sphenoid is orange
Bony Orbit:
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Orbit Vasculature:
ophthalmic artery which arises from the internal carotid artery
Drainage via the superior and inferior ophthalmic veins
can drain anteriorly into tributaries forming the frontal vein or posteriorly into the cavernous sinuses
Vasculature of the Orbit:
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Vasculature of the Orbit:
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Infection transmission from the eye:
- ophthalmic veins communicate
with venous drainage of the face
and the pterygoid plexus and pass
posteriorly to drain into the
cavernous sinus - dangerous because thrombosis in
the cavernous sinuses can
compress the internal carotid
artery and hence restrict blood
supply to the brain (middle
cerebral and anterior cerebral
arteries)
Innervation of the Orbit:
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Where is the apex of the bony orbit?
projects posteromedially
base projects anteriorly
(pyramid with apex inward)
Bony Orbit:
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Nasociliary Nerve:
- function
- sensory afferent to
- posterior ethmoidal air cells
- sphenoid air sinus
- eyelids
- nose
- anterior cranial fossa
- intrinsic muscles of the eye
Lacrimal Nerve:
- function
- sensory afferent to lacrimal gland
- ANS
- conjunctiva
- upper eyelid laterally
Frontal Nerve:
- function
- sensory afferent to conjunctiva,
upper eyelid, forehead
Bony Orbit:
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Bony Orbit: Innervation:
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Autonomic innervation of the Orbit: Parasympathetic Supply: Intrinsic Muscles of the Eye:
- Edinger-Westphal nucleus in
midbrain fibers pass through the - oculomotor nerve CNII
- ciliary ganglion
- short ciliary nerves
Parasympathetic Supply to Intrinsic Muscles of the Eye:
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Layers of the Eye:
Fascial Sheath:
- surrounds eyeball but not
anteriorly over cornea - thickens inferiorly forming the
suspensory ligament which holds
the eyeball - encloses muscles: lateral rectus,
inferior oblique, inferior rectus,
medial rectus
What are the check ligaments of the eye and what do they do?
- check ligament of lateral rectus
muscle - check ligament of medial rectus
muscle - continuation of fascia from lateral
and medial recti muscles - fix eyeball in orbit
- limit movement of eyeball,
prevents pupil disappearing
within the orbit
Function of the Lateral Rectus Muscle:
- pulls on the lateral aspect of the
eyeball - abduction of eyeball
Function of the Medial Rectus Muscle:
- pulls on the medial aspect of the
eyeball - adduct the eyeball
Layers of the Eye:
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The Layers of the Globe:
- external fibrous layer
- middle vascular layer
- internal neural layer
Globe: External Fibrous Layer:
- sclera: dense connective tissue,
attachment for extra-ocular
muscle after passing through the
fascial sheath, white opaque (white
of eye) - cornea: transparent, projects over
the iris and pupil
Globe: Middle vascular Layer:
- choroid: vascular, pigmented
- ciliary body: ciliary muscle, ciliary
processes, zonular fibers - iris: smooth muscle, coloured part
of the eye, dilator and sphincter
pupillae
Label the middle vascular layers of the eye:
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Label the external fibrous layers of the eye:
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Globe: Internal Layer:
- Retina is housed here
- non visual part = anteriorly
- optic has two aspects:
- pigmented layer = external =
absorbs excess light and prevents
reflections of light - neural layer = internal =
neurologically functional,
photosensitive layer
What separates the non-visual and optic parts of the retina?
ora serrata
Globe: Internal Layers:
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Macula Lutea:
- yellow spot
Optic Disc:
- retina
- blind spot
- cells that are part of the retina are
ganglia where axons come
together - no functional neural tissue
Fovea Centralis:
- middle of macula lutea
- important for highest level of
visual acuity - sharp defined vision
Globe Segments and Chambers:
anterior and posterior segments are divided by the lens
anterior segment is further divided into anterior and posterior chambers
the posterior segment = the vitreous
anterior chamber of anterior segment = cornea and conjunctiva to the iris
posterior chamber of anterior segment = iris to lens
Globe Structure:
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What does this diagram?
axis of eyeball and orbit is offset
muscles move more complicated
How many extra-ocular muscles and overall function?
- 7 muscles
- 6 move the eyeball
- 1 moves the eyelid
How to remember extra-ocular muscle actions?
- recti muscles move in the direction
of the muscle eg superior = up - superior oblique = depresses,
abduct, intort (internal rotation) =
down and out - inferior oblique = up and out
- levator palpebrae superioris =
contract to lift eyelid
Extra-ocular muscles: Recti Muscles:
- arise
- action
- arise from tendenous ring =
annulus - pass anteriorly to attach to the
anterior aspect of the sclera - superior rectus = upwards
- inferior rectus = downwards
- medial rectus = adduct
- lateral rectus = abduct
Extra-ocular Muscles:
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Extra-ocular Muscles: Obliques:
- from bony orbit itself not annula
- attaches to the posterior sclera of
globe - superior oblique = anatomical
action from trochlea = depresses,
abduct, intort (internal rotation) - inferior oblique = from maxilla
anatomical origin = elevate,
adduct, extort (external rotation)
Extra-ocular Muscles: Levator Palpebrae Superioris:
- action
contraction elevates eyelid
Extra-Ocular Muscle: Actions:
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Which nerve innervates the superior oblique muscle?
- CN IV
- trochlear nerve
Extra-ocular Muscles:
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Which nerve innervates the inferior oblique muscle, superior, medial, inferior recti and levatator palpaebrae superioris ?
- oculomotor nerve
- CN III
Which nerve innervates the lateral rectus muscle?
- CN VI
- abducens nerve
How to remember the innervation of extra-ocular muscles?
- SO4
- LR6
- else 3
Function of intrinsic extra-ocular muscles?
- control size of pupil
- control shape of lens
Intrinsic Extra-ocular muscles and what type of innervation?
- ciliary muscles = parasymp
- sphincter pupillae = pns
- dilator pupillae = sympathetic =
danger, see more
Eye diagram:
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What does the lacrimal apparatus comprise of?
- lacrimal gland
- lacrimal canaliculi
- lacrimal sac
- nasolacrimal duct
Where is the lacrimal apparatus located?
within the bony orbit
What is the function of the lacrimal apparatus?
production, maintenance and drainage of lacrimal fluid from the external surface of the eyeball
Lacrimal Apparatus:
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Lacrimal Gland:
- gland type
- location
- structure
- exocrine
- lacrimal fossa in roof of orbit
- divided into orbital and palpebral
parts by the levator palpebrae
superioris
Lacrima Gland: Arterial Supply:
Internal carotid artery provides ophthalmic artery which provides the lacrimal artery
What nerve innervates the lacrimal apparatus?
What type of innervation?
- CNV1 = ophthalmic division of
trigeminal - sensory
Lacrimal apparatus:
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Lacrimal Apparatus:
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Lacrimal Gland innervation:
- parasymp
- arises forom superior salivatory
nucleus and nucleus intermedius
(CNVII) (facial) - branches into the lacrimal nerve
Retina Structure:
- 3 neural cell types in neural layer;
external to internal - photoreceptor:
- rods = dim light sensitive
receptors - cones = bright light and colour
sensitive receptors
- rods = dim light sensitive
- bipolar neurons
- ganglion cells = myelinated axons
form the optic nerve and leave the
eyeball at the optic disc
Retina Pathway:
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Visual Pathway: Nomenclature:
info in superior aspect of nasal field will travel to inferior aspect of temporal field
and vice versa up and down, temporal and nasal are reversed for visual field to retinal field
cross-over and divergence of fibers at optic chiasm
optic tracts to lateral geniculate nucleus in thalamus
optic radiations to primary visual cortex = area 17
Visual Pathways:
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highest concentration of cones found in the
fovea centralis
