Anatomy Flashcards
what makes up the roof of the bony orbit?
the frontal bone
what makes up the lateral wall of the bony orbit?
sphenoid bone and zygomatic bone
what makes up the medial wall of the bony orbit?
ethmoid bone
lacrimal bone
frontal bone
maxillary bone
what makes up the floor of the bony orbit?
maxillary bone
why is the superior orbital margin more anterior than the inferior orbital margin?
allows eyeball to be protected from a blow larger than the diameter of the orbital rim
what is an orbital blowout fracture?
when an impact causes the medial wall or floor of the bony orbit to fracture but the orbital rim remain intact
what surrounds the eyeball?
periorbital fat
what neurovascular bundle is susceptible to injury in an orbital blow out fracture?
infraorbital neurovascular bundle
what muscle surrounds the orbital rim?
the orbicularis oculi
what are the 2 parts to the orbicularis oculi?
external- orbital part
internal- palpebral part
what is the function of the superior and inferior tarsi?
skeleton of the eyelid
give the eyelid it’s half moon shape
what muscle attaches to the superior tarsus?
levator palpebrae superioris
what is the function of the levator palpebrae superioris?
lifts the upper eyelid
what ligaments anchor the superior and inferior tarsi to the bone?
lateral palpebral ligament
medial palpebral ligament
what connective tissue are the tarsal glands within?
superior and inferior tarsi
what part of the eye is coloured?
iris
what covers the iris?
the cornea
what is the white part of the eye?
the sclera
what covers the sclera?
conjunctiva
what is the name of the opening that lacrimal fluids pass into?
punctum
what is the conjunctival fornix?
the angle on the lower and upper eyelid where conjunctiva of sclera and conjunctiva of eyelids meet
what duct takes lacrimal fluid from the punctum to the inferior meatus?
nasolacrimal duct
which nerve carries parasympathetic fibres to the lacrimal gland?
CN VII
what are the 2 parts to the fibrous outer layer of the eye?
- sclera
- cornea
what part of the eye has 2/3 of the refractory power?
the cornea
what are the 3 layers of the eye?
- fibrous outer layer
- uvea (vascular layer)
- retina
what are the 3 parts of the uvea?
- iris
- ciliary body
- choroid
what is the function of the iris?
changes the pupil diameter
what is the function of the ciliary body?
- changes shape of the lens
- secretes aqueous humour
what is the function of the choroid?
-nutrient and gas exchange
what separates the the anterior and posterior segment?
the lens
what are the 2 chambers of the anterior segment?
anterior and posterior chamber
what splits the anterior and posterior chambers of the anterior segment?
the iris
what fluid does the anterior chamber of the anterior segment contain?
aqueous humour
what fluid does the posterior chamber of the anterior segment contain?
aqueous humour
what is the function of the aqueous humour?
nourishes the lens and cornea because there are no vessels to do so
what fluid does the posterior segment contain?
vitreous humour
what is it called when the lens becomes clouded and opaque?
cataract
what is the name of the corneoscleral junction?
Limbus
where is the aqueous humour reabsorbed?
scleral venous sinus (canal of Schlemm) at the iridocorneal angle
what is the fundus?
the posterior area of the eye where light is focused
what does the fundus contain?
optic disc and macula
what is the centre of the macula?
fovea
what is the macula?
the area where there is the greatest density of cones
what are the three main layers of the retina?
A to P
axons of ganglion cells
ganglion cells
photoreceptors
light from the left visual field is processed in which visual cortex?
the right visual cortex
light from the right visual field is processed in which visual cortex?
the left visual cortex
blood from the ventral vein of the retina will drain to the cavernous sinus via which veins?
superior ophthalmic vein
inferior ophthalmic vein
what are the 7 extraocular muscles?
superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior obique levator palpebrae superioris
where do the extraocular muscles insert?
all onto the sclera
apart from levator palpebrae superioris which inserts into superior tarsus
where do the 4 rectus extraocular muscles originate from?
the common tendinous ring which surrounds the optic canal
what is the motor innervation of the medial rectus?
CN III
what is the motor innervation of the lateral rectus?
CN VI
what is the motor innervation of the superior rectus?
CN III
what is the motor innervation of the inferior rectus?
CN III
what is the motor innervation of the superior oblique?
CN IV
what is the motor innervation of the inferior oblique?
CN III
what is the motor innervation of the levator palpebrae superioris
CN III
what is intorsion of the eyeball?
medial rotation
what is extorsion of the eyeball?
lateral rotation
why do most extraocular muscles of the eye (except medial and lateral rectus) have secondary movements?
because the orbit axis is different from the optical axis
how do you test the superior rectus?
by asking patient to abduct (using lateral rectus) then asking to look up
how do you test the inferior rectus?
by asking patient to abduct (using lateral rectus) then asking to look down
why must you abduct or adduct the eyeball before testing extraocular muscles?
to isolate the muscle
rules out secondary functions of the other muscles
how do you test the superior oblique?
by asking patient to adduct (using medial rectus) then asking to look down
how do you test the inferior oblique?
by asking patient to adduct (using medial rectus) then asking to look up
what extraocular muscle cause medial rotation? (intorsion)
superior oblique
what extraocular muscle causes lateral rotation (extorsion)
inferior oblique
what extraocular muscles cause pure elevation?
superior rectus + inferior oblique
what extraocular muscles cause pure depression?
inferior rectus + superior oblique
what ligament holds the eye just above the floor of the orbit?
the suspensory ligament
why might unilateral orbital trauma cause diplopia?
if trauma is associated with zygomatic bone, the suspensory ligament of the eye can be displaced and the eye may be lowered causing diplopia
what cranial nerve is the infraorbital nerve a branch of?
V2
what type of fibres does the infraorbital branch of CN V2 contain?
sensory
what nerve supplies sensory fibres to the skin of the upper eyelid?
CN V1
what nerve supplies sensory fibres to the cornea?
CN V1
what nerve supplies sensory fibres to the conjunctiva?
CN V1
what nerve supplies sensory fibres to the dorsum of the nose?
CN V1
what nerve supplies sensory fibres to the skin of the lower eyelids?
CN V2
what nerve supplies sensory fibres to the skin over the maxilla?
CN V2
what nerve supplies sensory fibres to the skin of the ala of the nose?
CN V2
what nerve supplies sensory fibres to the mucosa of the upper lip?
CN V2
what nerve supplies sensory fibres to the mucosa of the lower lip?
CN V3
what nerve supplies sensory fibres to the skin over the mandible?
CN V3
what nerve supplies sensory fibres to the skin over the TMJ?
CN V3
what nerve supplies sensory fibres to the skin over the angle of the mandible?
the great auricular nerve from C2/3
what nerves are involved in the blink reflex?
V1 and VII
what nerve carries the afferent sensory limb of the blink reflex?
V1 (in long ciliary nerve)
what nerve carries the efferent motor limb of the blink reflex?
VII
what are the 3 cervical parts of the sympathetic trunk?
superior cervical ganglion
middle cervical ganglion
inferior cervical ganglion
from what vertebral levels can sympathetic axons leave the spinal cord?
T1 to L2
the sympathetic fibres of the internal and external carotid nerves come from which ganglion of the sympathetic trunk?
superior cervical ganglion
the ophthalmic artery is an intracranial branch of which artery?
internal carotid artery
the inferior cervical ganglion and the first thoracic ganglion often fuse to form what?
the stellate ganglion
what is the space between the pretrachial fascia and the prevertebral fascia called?
the retropharyngeal space
what fascial layer of the cervical neck does the vagus nerve sit within?
the carotid sheath
what cervical ganglion is involved in supplying the orbit with sympathetic supply?
superior cervical ganglion
which cranial nerves carry parasympathetic axons?
CN III, VII, IX, X
which cranial nerve relays parasympathetic nerves to the orbit?
CN III
CN III supplies parasympathetic axons to what?
the eye
CN VII supplies parasympathetic axons to what?
submandibular and sublingual salivary glands
lacrimal gland
CN IX supplies parasympathetic axons to what?
parotid salivary glands
CN X supplies parasympathetic axons to what?
organs of neck/chest and abdomen (as far as midgut)
CN III supplies parasympathetic axons to which ganglion?
ciliary ganglion
what are the 2 branches of CN III?
superior branch
inferior branch
what does the superior branch of CN III supply?
superior rectus
levator palpebrae superioris
what does the inferior branch of CN III supply?
medial rectus
inferior rectus
inferior oblique
ciliary ganglion
what within the orbit is under autonomic control?
diameter of iris
and shape of lens
the long ciliary nerve contains what type of nerve fibres?
sympathetic and sensory (from CN V1)
the short ciliary nerve contains what type of nerve fibres?
parasympathetic (from CN III) and sympathetic
both sympathetic and parasympathetic nerve axons pass through the ciliary ganglion, which ones synapse here?
parasympathetic axons
sympathetic axons have already synapsed in the sympathetic trunk
what reflex causes stabilisation of gaze during head movements?
vestibulo-ocular reflex
which autonomic system is involved in opening the eyes wider?
sympathetic
which autonomic system is involved in closing the eyes?
parasympathetic function
what autonomic system is involved in contracting the pupil?
parasympathetic function
what autonomic system is involved in dilating the pupil?
sympathetic function
what autonomic system is involved in focussing on near objects?
parasympathetic function
what autonomic system is involved in focussing on far objects?
sympathetic function
what autonomic system is involved in emotional lacrimation?
sympathetic function
what autonomic system is involved in reflex lacrimation?
parasympathetic function
what muscles cause the dilation of the pupil?
dilatory pupillae fibres
what muscles cause the contraction of the pupil?
sphincter pupillae fibres
the dilator pupillae fibres are under what autonomic control?
sympathetic
the sphincter pupillae fibres are under what autonomic control?
parasympathetic
what is the name for a non-physiologically enlarged pupil?
mydriatic pupil
what is type of drugs induce dilation of the pupil?
mydriatic drugs
what is a fixed pin point pupil?
a pupil which is very constricted and has no response to light
what type of drugs cause a fixed pin point pupil?
opiate drugs
what is the name for a non-physiologically constricted pupil?
miotic pupil
what is a fixed-dilation pupil?
a pupil which is very dilated and has no response to light
what pathology does a fixed dilation pupil indicate?
CN III pathology
parasympathetic axons are inhibited
which nerve carries the afferent limb of the pupillary light reflexes?
CN II
what connects the ciliary body to the lens?
suspensory ligament
what happens when the ciliary body contracts?
the suspensory ligament relaxes, and the lens becomes spherical (for short distance)
what happens when the ciliary body relaxes?
the suspensory ligament tightens and the lens becomes flat (for long distance)
what muscle is like a sphincter around the ciliary body?
smooth ciliary muscle
contraction of the ciliary muscle is under control of what autonomic system?
parasympathetic
what nerve is involved in the afferent limb of the tear reflex? (in response to mechanical or chemical stimulation)
CN V1
what nerve supplies parasympathetic fibres to the lacrimal gland?
greater petrosal nerve
what cranial nerve is the greater petrosal nerve a branch of?
the facial nerve
what is an early sign of raised ICP which is easy to spot?
fixed dilated pupils
what are the meninges?
membranes that surround the brains:
dura
arachnoid
pia
why are the optic nerves considered as CNS extensions?
because meninges surround them
where is the subarachnoid space found?
between the arachnoid mater and the pia mater
what are the 2 layers of the dura mater?
endosteal layer
meningeal layer
what is enclosed between the layers of dura mater?
dural venous sinuses
what fills the subarachnoid space?
CSF,
some blood vessels run through
where is the CSF made?
choroid plexus of the ventricles
the CSF is reabsorbed intot he dural venous sinuses via what?
arachnoid granulations
what are the 4 ventricles?
left lateral ventricle
right lateral ventricle
3rd ventricle
4th ventricle
what are ventricles of the brain?
CSF filled spaces
where is the right lateral ventricle located?
within the right cerebral hemisphere
where is the left lateral ventricle located?
within the left cerebral hemisphere
where is the 3rd ventricle located?
within the diencephalon
where is the 4th ventricle located?
betweent the cerebellum and the pons
what connects the 3rd and 4th ventricles?
the cerebral aqueduct
describe the circulation of CSF through the ventricles?
secreted in choroid plexus of lateral ventricles, passe into third ventricle then via cerebral aqueduct into the fourth ventricle
from the 4th ventricle where does CSF go?
mainly into subarachnoid space
some passes into central canal of spinal cord
compare the margins of a healthy optic disc to a swollen optic disc?
healthy: clear margins
swollen: blurred margins
what are the 3 main effects of CN III damage?
- dilated pupil
- ptosis
- eye turned inferolaterally
why does CN III damage cause a dilated pupil?
loss of parasympathetic supply to sphincter pupillae
why does CN III damage cause ptosis?
loss of levator palpebrae superioris function
why does CN III damage cause the eye to be turned inferolaterally?
loss of SR, IR, MR and IO function
unopposed action of SO (and LR)
what is the main effect on the orbit of CN IV damage?
eye cannot move inferomedially
why can the eye not move inferomedially with CN IV damage?
loss of superior oblique function
what is the main effect of CN VI damage?
eye cannot move laterally
why can the eye not move laterally with CN VI damage?
loss of lateral rectus function
how many neurones are involved in the pupillary light reflex?
4
describe the first neurone in the pupillary light reflex?
from retina to pretectal nucleus in the midbrain via CN II
describe the second neurone in the pupillary light reflex?
from pretectal nucleus to edwinger westphal nucleus
what is found in the edwinger westphal nucleus?
cell bodies of parasympathetic axons of CN III
describe the third neurone in the pupillary light reflex?
from edwinger westphal nucleus to ciliary ganglion via inferior division of CN III
describe the fourth neurone in the pupillary light reflex?
from cililary ganglion to sphincter pupillae muscles via short ciliary nerve
which neurones in the pupillary light reflex are unilateral?
1st neurone
which neurones in the pupillary light reflex are bilateral?
2nd, 3rd, 4th neurones
