Head & Neck special senses Flashcards
whats the function of the eye
self-focus light
adjusts light intensity
converts light into electrical impulses interpreted by brain
where are orbits located
upper half of face below anterior cranial fossa and anterior to the middle cranial fossa
whats the bony orbit
a pyramidal bony cavity of facial skeleton
the apex of the bony orbit extends
posteromedially -towards optic cavity
what 7 bones contribute to the framework of each orbit
maxilla
zygomatic
frontal
ethmoid
lacrimal
sphenoid
palatine
the bony orbit is lined by
periorbita which is fascia sheath of the eye
the periorbita is continuous at
optic canal
superior orbital fissure
inferior orbital fissure
dural fascia
what are the contents of the orbit
eyeball
optic nerve
extra-ocular muscles
lacrimal apparatus
adipose tissue
fascia
nerves and vessels
conjunctival sac
the orbital margin is formed by what bones
frontal
maxillary
zygomatic
how many walls does the orbit have
4 and apex
the superior wall (roof) of the orbit is formed by
orbital part of the frontal bone which has lacrimal fossa with lacrimal gland
lesser wing of sphenoid near the apex
the medial wall ( paper thin wall) of the orbit is formed by
ethmoid bone
frontal bone
lacrimal bone
sphenoid bone (body)
medial wall of the orbit is indented by
lacrimal fossa for lacrimal sac
what separates the 2 medial walls of the orbit
ethmoid sinuses
nasal cavity
what forms the inferior wall (floor) of the orbit
maxilla bone at the orbital surface
part of zygomatic and palatine bones
the lateral wall of the orbit is formed by
frontal process of zygomatic bone
greater wing of sphenoid bone
where is the apex of the orbit
at optical canal in lesser wing of sphenoid b one, medial to superior orbital fissure
what can cause exophthalmos
fracture of the orbit
blowout fracture- where there is intra-orbital bleeding
periorbital ecchymosis-where blows to periorbital causes bleeding and swelling
orbital tumors
what do eyebrows do
provide shade and are a shield for perspiration
what are eyelids (palpebrae)
skin covered folds with tarsal plates made of connective tissue
what does levator palpebrae superioris muscle do and what innervates it
opens eye
occulomotor nerve
superior tarsal muscle portion is what and what innervates it
smooth muscle
post ganglion sympathetic fibers
what accounts for accumulation of fluid (blood) when injured during periorbital ecchymosis
thin layer of connective tissue and loose arrangement
whats the sensory innervation of the eyelids
supra-orbital, supra-trochlear, infra-trochlear, infra-orbital nerves (v2) which are terminal branches of the frontal nerve, which is the largest branch of the ophthalmic division of the trigeminal nerve
whats the motor innervation of the eyelids
branches of the :
facial nerve (CN VII) which innervates palpebral part of orbicularis oculi
oculomotor nerve (CN III) which innervates levator palpebral superioris
sympathetic fibers which innervate superior tarsal muscle
what is the canthus
the corner of the eye
what does the lacrimal caruncle make
eye sand at medial corner
what do tarsal glands make
oil to slow drying of canthus
eyelash has what gland at the hair follicule
ciliary gland
eyelashes are sensitive to
touch
what does the mucous membrane of the eye do
it coats the inner surface of the eyelid (palpebral part) and then folds back onto the surface of the eye (ocular part)
what is the mucous membrane of the eye
a thin layer of connective tissue which is transparent
and shows blood vessels underneath (blood-shot eyes)
what lines the mucous membrane of the eye
stratified columnar epithelium with goblet cells which secrete mucous to keep eyes moist
why is vitamin A necessary for all epithelial secretions
because its lack leads to conjunctiva drying up and the formation of scaly eye
lacrimal apparatus is involved in
production, movement and drainage of fluid on the surface of the eyeball
the lacrimal apparatus is composed of
lacrimal glands
lacrimal duct (nasolacrimal duct)
tears
describe the components of the lacrimal apparatus
lacrimal glands- which are superficial/lateral in orbit and produce tears
lacrimal duct- is in the medial corner of the eye and carries tears to the nasal cavity (is closed in newborns and usually opens by 1 yr)
tears- contain mucous, antibodies and lysozyme (anti-bacterial)
whats the pathway for tears
they’re produced by the lacrimal gland~ then spread over eyeball~ then enter the lacrimal lake~ then Lacrimal canaliculi~ then lacrimal sac~ then nasolacrimal duct~ and out trough the inferior nasal meatus
what are the 2 groups of muscles within the orbit
extrinsic muscles- which are involved in movement of the eyeball and raising upper eyelids
intrinsic muscles- which control the shape of the lens and size of the pupil
extrinsic muscles of the eye include
levator palpebrae
superior rectus
inferior rectus
superior oblique
inferior oblique
medial rectus
lateral rectus
what innervates the eye muscles
oculomotor
abducent
trochlear
innervation of the muscles of the eye can be summarized as
SO4, LR6 and remainder 3 i.e.
Superior oblique is innervated by trochlea (CN IV)
Lateral rectus is innervated by abducens (CN VI)
The remaining 3 muscles are innervated by oculomotor nerve (CN III)
what are the eye movements
elevation- moving pupil superiorly
depression-moving pupil inferiorly
abduction- moving the pupil laterally
adduction- moving the pupil medially
whats intorsion (internal rotation) of the eye and what causes it
medial (inward) rotation of the upper pole of cornea
superior oblique and superior rectus
whats extorsion (external rotation) of the eye and what causes it
lateral (outward) rotation of the superior pole of the cornea
inferior rectus and inferior oblique
axis of each orbit is directed
slightly lateral
axis of each eyeball is directed
anteriorly
whats the origin and insertion of the levator palpebrae superioris muscle
lesser wing of sphenoid to insert at the anterior surface of the tarsal
whats the function and innervation of the levator palpebrae superioris
elevation of upper eyelid
oculomotor nerve (CN III)
superior tarsal muscle is what type of muscle
is innervated by
and does what
smooth muscle
post ganglion sympathetic fibers from superior cervical ganglion
maintains eyelid elevation
loss of function of either levator palpebrae or superior tarsal muscle results in
ptosis or drooping of the upper eyelid
loss of innervation of orbicularis oculi by facial nerve causes
inability to close the eye tightly and the lower eyelid droops away spilling tears
loss of innervation of levator palpebral superioris by oculomotor nerve causes what
inability to open the upper eyelid voluntarily producing a complete ptosis
loss of innervation of superior tarsal muscle by sympathetic fibers causes
constant partial ptosis
what causes Horner’s syndrome
lesion e.g. tumor eroding the cervicothoracic ganglion which leads to sympathetic function in the head
Horner’s syndrome is characterized by
pupillary constriction (miosis)- which is paralysis of the pupillary dilator muscle
partial ptosis- which is paralysis of the superior tarsal muscle
absence of ipsilateral sweating (loss of sweating of the face)
where do the rectus muscles of the eye originate from
a common tendinous ring at the apex of the orbit
where do the superior and inferior rectus muscles insert
anterior half of the eyeball - hence directed laterally
what is the movement and innervation of the:
superior oblique
lateral rectus
medial rectus
superior rectus
inferior rectus
inferior oblique
depresses eye, turns medially- trochlear (CN IV)
turns laterally -abducens (CNVI)
turns medially- oculomotor (CN III)
elevates- oculomotor (CN III)
depresses eye- oculomotor (CN III)
elevates eye, turns laterally- oculomotor (CN III)
what is strabismus
a vision disorder in which the eyes don’t properly align when looking at an object (the eye thats focused on an object can be altered)
strabismus can be categorized by
the direction of the turned or misaligned eye i.e.
inward turning (esotropia) outward turning (exotropia) upward turning (hypertropia) downward turning (hypotropia)
what are the 3 layers of the eye
outer fibrous layer
middle vascular (pigmented) layer
inner layer
a lesion at CN III will cause
complete ptosis (drooping of upper eyelid)
the external white fibrous coat of the eyeball consists of
sclera and cornea
whats the sclera
the white fibrous layer covering 5/6 of the eye
whats the cornea
the transparent structure forming the anterior 1/6 of the outer coat
the middle vascular pigmented coat of the eyeball consists of
the choroid
ciliary body
iris
whats the choroid and its function
outer pigmented and inner vascular layer which invests 5/6 of the eye
it nourishes the retina and darkens the eye
whats the ciliary body
the thickened portion of the vascular coat between the choroid and iris
what does the ciliary body consist of
ciliary ring
ciliary processes
ciliary muscles
whats the iris
the thin contractile circular pigmented diaphragm with central aperture pf the pupil
the internal nervous coat consists of
retina - which is the outer pigmented inner nervous
whats the posterior and anterior part of then internal nervous coat like
posterior part- photosensitive
anterior part- not photosensitive
what does the optic disc (blind spot) consist of
optic nerve fibers formed by axons of ganglion cells which connect to rods and cones
the optic disc has no
receptors hence is not photosensitive
