Anatomy Flashcards
bones of the bony orbit
frontal ethmoid zygomatic maxilla lacrimal palentine nasa sphenoid
where is the optic canal located in relation to the bony orbit
posteromedially
what is the gap between the greater/lesser sphenoid wing called and what passes through it
superior orbital fissure
cranial nerves III, IV, VI
what bone is the supraorbital notch found on and what is in it
frontal
supraorbital neurovascular bundle with supraorbital nerve as a branch of opthalamic branch of trigeminal
what bone is the infraorbital foramen found on and what is in it
maxilla
infraorbital neurovascular bundle with infraorbital nerve as a branch of maxillary division of the trigeminal
the bony orbit can be described as a pyramid shape. what is the base of this ‘pyramid’ known as
orbital rim
the eyes face ____ and the bony orbit faces ___ and so they do/dont line up
anterior
anterolateral
they dont line up
describe how the eye is protected by the bony rim
superior overhangs inferior to prevent eye trauma
bones are quite strong
what is a blowout fracture
traumatic strike to the bony rim carries energy back to the orbital plates and causes fracture
besides a blowout fracture where else is a fracture common after strike to bony orbit
orbit rim sutures
where are the bony plates found
frontal bone superior
ethmoid bone medially
maxilla inferiorly
most superficial muscle to the eyelid, function and innervation
orbicularis oculi
orbital - tight closing of eye
palpebral part for gentle eye closing
facial nerve CN VII
what muscular thick layer is deep to orbicularis oculi
superior and inferior tarsus
function of LPS and attachment
elevates superior eyelid
attaches to superior tarsus and superior eyelid
originates from lesser wing sphenoid
function of tarsus gland
produces lipids to prevent tears overflowing
describe the flow of lacrimal fluid over the eye and drainage
washes over eye lateral to medial and drains through canaliculi to lacrimal puncta, moving to lacrimal sac and nasolacrimal sac
drains to inferior meatus of nasal cavity
rectus muscles of the eye?
superior rectus
inferior rectus
lateral rectus
medial rectus
oblique muscles of the eye?
superior oblique
inferior oblique
what does the inferior oblique originate from and what does it attach to
originates from orbital plate of the maxilla and inserts onto the sclera
innervation to the muscles of the eye
LR6 SO4 AO3
lateral rectus is CN IV
Superior oblique is CN IV
all others are CN III
what covers the sclera of the eye
conjunctiva
what covers the iris of the eye
cornea
true/false - cornea receives nutrient from small conjunctival vessels
false - it is avascular and receives its nutrient from lacrimal fluid and aqueous
what is the conjunctival fornix
junction where the conjunctiva is reflected from the sclera to the eyelid
what is the limbus of the eye
corneoscleral junction
layers of the eye?
fibrous
uvea
retina
contents of the fibrous layer of the eye
sclera
cornea
contents of the uvea
iris
ciliary body
choroid
what is the anterior segment and what can it be subdivided into
segment of eye in front of lens
anterior chamber between iris and cornea
posterior chamber between iris and suspensory ligaments
what is the posterior segment of the eye and what makes it up
behind lens of the eye
made up of vitreous body, jelly like to transmit light and hold the retina in place
describe the circulation of aqueous in the anterior segment of the eye
ciliary processes secrete aqueous
circulates through posterior chamber and nourishes lens
passes into anterior chamber and nourishes cornea
reabsorbed by scleral venous sinus at iridocorneal angle
describe the venous drainage of the eye
superior/inferior opthalmic veins drain to cavernous sinus through superior orbital fissure
central vein drains direct to cavernous sinus
some smaller veins frain to the pterygoid plexus
what is the danger triangle of the face and why is it possibly dangerous
upper lip to external nose
all facial and forehead veins within the danger triangle drain to the cavernous sinus and cranial cavity
means superficial infections can spread deep to cranial cavity
describe the arterial supply of the eye
internal carotid passes to opthalmic artery and passes optic canal to supply eyeball, lacrimal gland, muscles, forehead, scalp
ciliary arteries supply choroid
centra artery to retina
what is important about the arterial and venous drainage of the retina
they are end arteries/veins so occlusion leads to tissue ischaemia and death
what is the fundus
posterior layer where light is focused
optic disk, macula, fovea
what is the optic disk
point of CNII formation
only point of entry for blood vessels and axons of CN II
true/false - the optic disk is a visual blind spot
true
what is the macula
greatest density of cones
what is the fovea
centre of macula and area of most acute vision
layers of the optic disk and retina?
photoreceptors - posterior and sense light
ganglion cells - ant to photoreceptors and synapse photoreceptors for light perception
axons of ganglion cells - come together to form optic nerve
describe the visual pathway
light enters the nasal and temporal retina of the eye
this enters the optic nerve and then enters the optic chiasma
nasal visual field crosses over to other side of the chiasm and combines with temporal to form optic canal
synapse with genicular bodies to form optic radiation
enters visual cortex
movement of superior rectus and innervation
can only elevate in abduction
CN III
movement of inferior rectus and innervation
when held in abduction can only depress
CN III
movement of medial rectus and innervation
can only adduct eyeball
CN III
movement of lateral rectus and innervation
can only abduct eyeball
CN IV
brings line of gaze into path superior and inferior rectus
movement of superior oblique and innervation
when in adduction it can only depress
CN IV
movement of inferior oblique and innervation
when in adduction can only elevate
CN III
describe pure elevation
inferior oblique and superior rectus
synergistically elevate eyes
antagonistically rotates eyes
describe pure depression
superior oblique and inferior rectus synergistically depress eyes and are antagonists to adduct/abduct
what muscles mediate bilateral eye movement at the same time
yolk muscles
for testing elevation and depression of the eyes, why does the testing of superior and inferior retus need done in abduction
to correctly angle the origin and attachment to allow for accurate true eye movements
describe the passage of sympathetic innervation to the orbit
exits T1 and passes up sympathetic chain to superior cervical ganglion
enters internal/external carotid nerves and pass on surface of int/ext carotids
opthalamic artery carries sympathetic axons to orbit
what cranial nerves are parasympathetic
sacral outflow
CN III, VII, IX, X
describe parasympathetic innervation to the orbit
parasympathetic, mainly CN III, synapses in ciliary ganglion
true/false - sympathetics and sensory fibres also synapse in ciliary ganglion
false - they can pass through it but they dont synapse
describe the path of CN III
connects with CNS at pons/midbrain
passes through cavernous sinus
exits supraorbital fissure
splits into superior/inferior division
sensory innervation of the opthalmic division trigeminal
upper eyelid cornea conjunctiva tip of nose forehead
sensory innervation of the maxillary division of the trigeminal
lower eyelid and maxilla
sensory innervation of the mandibular division of the trigeminal
sensory to mandible and TMJ
motor for muscles of mastication
describe the blink reflex
APs conducted from cornea to CN V1, carried to trigeminal ganglion to CN V and then to pons
connection to facial nerve
motor AP carried down CN VII to ocularis oculi
what is the vestibulo-ocular reflex and what nerves mediate it
turning of eye in opposite to head movement on focusing on object to stabilise gaze
CN VIII, CNIII, IV, VI
hat is the oculocardiac reflex and what nerves mediate it
reflex bradycardia in response to tension on extraocular muscles or pressure on eye
mediated by CN V1 and CNX
parasympathetic actions on the eye
less light into eyes
focus on near objects
reflex lacrimation to wash away foreign stimuli and clean cornea
sympathetic actions on the eye
opens eye wider
more light into eyes
what is muellers muscle and what innervates ir
elevates eyelid marginally
small slip of smooth muscle off LPS that has sympathetic innervation
describe pupillary constriction
parasympathetics constrict by sphincter pupillae muscles
describe pupillary dilation
sympathetic widens pupil by activating dilator pupillae muscles
origin and insertion of dilator pupillae muscles?
radially arranged
fixed onto external iris
mobile on the internal circumference of iris
what is a mydriatic pupil
non-physiologically enlarged pupil
what may cause mydriatic pupil
mydriatic drugs
what is a miotic pupil
non-physiologically constricted pupil
what may cause a miotic pupil
horners syndrome
what may cause a blown pupil
CN III pathology
what may cause fixed pin point pupils
opiate drugs
describe the path of the pupillary light reflex
bright light is shone into eye and this interpretation is taken by optic nerve to ipsilateral pretectal nucleus in the brain
stimulates BOTH edinger westphal nuclei in the midbrain
CN III carries motor function to pupils to cause bilateral constriction in stimulated and consensual eye
describe lens accommodation in far vision
parasympathetic innervation causes relaxation of the ciliary body to lead to tightening of the suspensory ligaments and flattening of the lens to accommodate farther light as it requires less refraction
describe lens accommodation in close vision
sympathetic innervation causes contraction of the ciliary body leading to slackening of suspensory ligaments and the rounding of the lens
this leads to more accommodation of closer objects in vision as they require more refraction
what are the function of basal tears
corneal health
cleans/nourishes and hydrates cornea
contains lysozyme
what are the function of reflex tears and what are the afferent/efferent nerves controlling
extra tears in response to mechanical/chemical stimuli
afferent is CN V1
efferent is facial VII
what are the types of tears
reflex
basal
emotional
describe reflex lacrimation in response to ANS innervation
parasympathetic
facial nerve carries APs through internal acoustic meatus
passes through synapse with geniculate ganglion and branch that goes through pterygoid canal to enter pterygopalentine ganglion
joins with CN V1/2- these dont have lacrimal innervation
what provides sensory supply to dura mater
trigeminal nerve
what sinuses are enclosed in the dura mater
dural venous sinuses
what is found in the subarachnoid space
CSF and blood vessels
where is the subarachnoid space accessed in a lumbar puncture and when does it end
L3/4 or L4/5
S2
describe CSF production and circulation in the brain
produced in choroid plexus in lateral and third ventricles
passes from R/L lateral ventricles to midline third
then through cerebral aqueduct to 4th
then subarachnoid space and central canal
reabsorbed by subarachnoid granulations into dural venous sinuses
what is the monro-kellie hypothesis
describes how pressure within the intracranial cavity must remain constant
what may cause raised ICP
any condition causing swelling of the brain or increased pressure surrounding the brain
true/false - most patients with raised ICP have visual problems
true
what does ICP normally sit around and what level requires intervention
5-15
>20
what is papilloedema
raised ICP causing compression on the optic tracts/nerves
this leads to bulging/swelling of optic disk as well as compression of the central artery/vein of the retina
visual symptoms associated with papilloedema
transient visual obscuration
flickering
blurred vision
decreased colour perception
what are the dura septae and why are they clinically relevant in raised ICP
brain can herniate through these folds of dura mater in raised ICP and cause cord compression or cranial nerve compression/stretch
what may raised ICP do to CN III and how may this present
compression/stretch oculomotor if medial lobe herniates through temporal notch
paralysis of sphincter pupillae
slow/lost pupillary light reflex, dilated pupil, ptosis, inferolaterally turned eyelid
what may raised ICP do to CN IV and how may this present
prone to trauma as winds around midbrain and stem
paralysis of SO so eye cannot move inferomedially
diplopia when looking down
eye may be more fixed upwards due to IO
what may raised ICP do to CN VI and how may this present
susceptible to damage by petris ridge of temporal bone
paralysis of LR muscle so eye cannot move laterally or may be medially deviated
