Anatomy Flashcards
what is the iris?
thin diaphragm
what does the iris control?
size of the pupil which is an opening in the iris
what is sclera covered by?
conjunctiva
what is the iris covered by?
cornea
what are the three layers of the eye?
- fibrous (outer layer)
- uvea (vascular/middle layer)
- retina (photosensitive/ inner layer)
what does the fibrous layer consist of?
sclera
cornea
what does the uvea consist of?
iris
ciliary body
choroid
what are the two segments of the eye?
- anterior segment
2. posterior segment
where is the anterior segment?
in front of the lens
what is the anterior segment split into?
anterior chamber
posterior chamber
where is in the anterior chamber?
between cornea and iris
where is the posterior chamber?
between iris and suspensory ligaments
where is the posterior segment?
behind the lens
what does the posterior segment contain?
vitreous body to secrete vitreous humour
collagen can clump together to form floaters
what secretes aqueous?
ciliary body has ciliary processes that secrete aqueous
where is aqueous reabsorbed?
Canal of Schlemm at the iridocorneal angle
role of aqueous
nourishes avascular structures
describe the arterial supply to the eye
ICA gives off the ophthalmic artery which branches into ciliary arteries and central artery of the retina
how does the ICA get into the cranial cavity?
carotid canal
what does the ophthalmic artery pass through?
optic canal
what is the fundus?
area on the retina where light is focused
what does the fundus contain?
optic disc
macula
fovea
what is the optic disc?
CNII formation
point of entry/exit for blood vessels and axons
where is the fovea found?
centre of the macula
where are objects in the right visual field processed in the brain?
left visual cortex
what are the 6 extraocular muscles?
lateral rectus superior rectus inferior rectus medial rectus inferior oblique superior oblique
role of LR
abduct the eye
brings into plane of SR and IR
role of SR
when in abduction, it elevates
role of IR
when in abduction, it depresses
role of MR
adducts
brings into plane of SO and IO
role of IO
when in adduction, it elevates
role of SO
when in adduction, it depresses
innervation of the extraocular muscles
LR6, SO4, AO3
role of levator papillae superioris
elevates the eyelid
innervation of levator papillae superioris
CNIII
what does the SO run through before inserting onto sclera?
trochlea
where do all the rectus muscles originate from?
common tendinous ring (annulus ring)
where does SO originate from?
sphenoid
where does IO originate from?
maxilla
where do all the extraocular muscles insert?
sclera
what supplies somatosensory innervation to the face?
CNV
what does CNV1 (ophthalmic division) provide sensation to?
upper eyelid
cornea
conjunctiva
what branch of CNV1 supplies the face and how does it get there?
supraorbital branch passes through the supraorbital foramen
+ nasal skin branches
what does CNV2 (maxillary branch) provide sensation to?
skin of lower eyelid
skin over maxilla
what branch of CNV2 supplies the face and how does it get there?
infraorbital nerve via the infraorbital foramen
what does CNV3 (mandibular branch) provide sensation to?
skin over mandible
TMJ, except angle of the mandible
what is the corneal reflex?
blinking
describe the pathway of the corneal reflex?
AP conducted from cornea via CNV1 to trigeminal ganglia along CNV to pons to CNVII to orbicularis oculi
sympathetic effect on the eye
opens eyes wider
gets more light into the eyes
focuses on far objects
parasympathetic effect on the eye
less light (protection/ when asleep)
focus on near objects
reflex lacrimation
what is the vestibulo-ocular reflex?
eyes turn in opposite direction to head movement
stabilises gaze
cranial nerve connections in vestibulo-ocular reflex
CNVII and CNIII, IV and VI
what is the oculocardiac reflex?
reflex bradycardia in response to tension in extraocular muscles/ pressure on eye
what division of the nervous system is involved in pupillary constriction?
parasympathetic innervation along CNIII to sphincter pupillae
what is pinpoint pupils an issue with?
pontine
what division of the nervous system causes pupillary dilation?
sympathetic innervation to dilator pupillae
what is the pupillary light reflex?
response to shining light into the eye causes pupillary constriction of both eyes
what nerve connections are involved in the pupillary light reflex?
ipsilateral CNII
midbrain (PTN > EWN > ciliary ganglion > ciliary nerve)
bilateral CNIII (direct and consensual response)
what is the lens accommodation reflex?
changes in the lens shape to look at close and distant objects
lens accommodation reflex in far vision
ciliary muscle relaxes causing ligaments to tighten and lens to flatten
lens accommodation reflex in near vision
ciliary muscle contracts
ligaments relax
lens adopts a spherical shape
what cranial nerve is responsible for the lens accommodation reflex?
CNIII
three types of lacrimation
- basal tears
- reflex tears
- emotion
what bones make up the orbit?
frontal zygomatic maxillary sphenoid ethmoid lacrimal
which bones have orbital plates?
frontal
ethmoid
maxillary
what are orbital plates?
areas of thinner bone that are more likely to fracture
what is a blow-out fracture?
pressure is transferred to orbital plates causing fracture
what is a trapdoor fracture?
contents such as fat, muscle, nerves can herniate through a blow-out fracture
location of the optic canal in the orbit?
posteromedial
which bone is the superior orbital fissure found?
sphenoid bone
what does the superior orbital fissure allow passage of?
CNIII
CNIV
CNVI
what is the external eyelid composed of?
orbicularis oculi
what are the two parts of orbicularis oculi and their roles?
orbital (screwing shut)
palpebral (gentle closure)
what is the internal eyelid composed of?
fibrous skeleton of superior and inferior tarsus with medial and lateral palpebral ligaments and orbital septum
what are tarsal glands?
glands in the eyelid that secrete lipids to line the eyelid and stop lacrimal fluid overflowing
where is the lacrimal gland located?
superolateral
what innervates the lacrimal gland?
CNVII
what does the lacrimal gland do?
produces fluid that passes into the cornea and washes over it collecting medially at the lacrimal lake
where does the lacrimal gland fluid drain?
lacrimal puncta into canaliculi through the lacrimal sac into the nasolacrimal duct (inferior nasal meatus)
pathway of sympathetic innervation to the head and neck
AP exit T1 and ascend within the sympathetic chain to superior cervical sympathetic ganglion
travels with ICA and ECA following opthalmic artery into the orbit
what are the four parasympathetic ganglia in the head and neck?
ciliary
pterygopalatine
otic
submandibular
what cranial nerve synapses in the ciliary ganglia?
CNIII to become the ciliary nerve
what do the meninges cover?
brain and spinal cord
layers of the meninges
dura mater (CNV)
arachnoid mater
sub-arachnoid space
pia mater
what level does the spinal cord end?
L2
what level does the subarachnoid space end?
S2
describe circulation of CSF
- secreted by choroid plexus in lateral and third ventricles
- flow into 4th ventricle via the cerebral aqueduct
- drains into sub-arachnoid space and is reabsorbed by arachnoid granulations
- passes into dural venous sinuses
why do people with raised ICP report visual symptoms?
optic nerves are also covered by the meninges
pressure is transmitted and can compress the nerve, central artery or vein of the retina
leads to papilloedema
CNIII oculomotor nerve palsy cause
compressed due to herniate of the uncal (medial lobe)
presentation of oculomotor nerve palsy CNIII
slowed light reflex dilated pupil ptosis eye down and out loss of accommodation
what can damage the CNVI?
stretching as it runs through the dura
presentation of CNVI palsy
eye is unable to move lateral causing medial deviation
presentation of CNIV palsy
on adduction there is upwards movement as IO is unopposed
