Lab 8: Eye and Ear Flashcards
1
Q
eye
A
- sensory organ that comprises a fluid filled globe (eyeball) with light-sensitive receptors that is contained within a bony cavity (orbit) of the skull
- orbit contains muscles that move the eye as well as well as fat, nerves, blood vessels, and the lacrimal apparatus
- orbit and eyeball are guarded anteriorly by 2 thin, moveable folds -> eyelids
2
Q
eyelids
A
- palpebrae
- help protect the eye from injury
- elliptical opening between them is the palpebral fissure
- where the eyelids meet they form rounded medial canthus and a more acute lateral canthus
- lateral canthus lies in direct contact with the eyeball -> medial doesnt
- lids are covered externally by skin and lined internally by a clear thin mucous membrane -> conjunctiva
- palpebral conjunctiva is continuous with the bulbar conjunctiva that covers the eyeball
- medial canthis is separated from eyeball by small pink space in the center of which is a small bump -> lacrimal caruncle
- lateral to lacrimal caruncle is a short curved fold of tissue -> plica semilunaris
- lacrimal punctum- black dot on the medial end of each eyelid -> opening to the lacrimal canal that leads to lacrimal sac
3
Q
sclera
A
- white of the eyeball
- covered by transparent bulbar conjunctiva
4
Q
cornea
A
- forms a transparent bulge on the front of the eyeball
- cornea is avascular
- has no lymphatic drainage
- deep to the cornea is the iris (pigmented)
- center of iris is pupil
- transparent
- anterior bulging of sclera
5
Q
bony orbit
A
- 7 bones
- frontal- makes up the superior margin and roof of the orbit
- zygomatic- makes up the lateral margin and part of the lateral wall
- maxilla- comprises the floor and much of the inferior and medial margins
- lacrimal- makes up the medial wall anteriorly
- ethmoid- makes up the medial wall posteriorly
- sphenoid- constitutes the back of the cavity and much of its lateral wall
- palatine bone- has a thin process that projects upward to contribute a tiny triangular wedge to the back of the orbital floor between the maxilla and ethmoid
- floor and medial wall of the orbit have comparatively thin walls separating the orbital cavity from the sinuses that occupy the maxilla and ethmoid bones
6
Q
optic canal
A
- pierces the lesser wing of the sphenoid
- conveys the optic nerve
7
Q
superior orbital fissure
A
- greater and lesser wings of the sphenoid are separated by the superior orbital fissure
- conveys the oculomotor, trochlear, ophthalmic division of trigeminal, and abducens nerves
8
Q
thin inferior orbital fissure
A
-a thin inferior orbital fissure separates the sphenoid and maxilla
9
Q
lacrimal bone
A
- has a sharp crest
- together with a crest along the frontal process of the maxilla, it defines a hollow known as the lacrimal fossa
- continuous inferiorly with the nasolacrimal canal -> opens into the nasal cavity below the inferior nasal concha
10
Q
eyelids: tarsal plates
A
- has a fibrous skeleton (tarsal plate) that is lined on the outside by muscle, superficial fascia, and skin and on the inside by modified sebaceous glands and a thin, transparent mucous membrane
- upper lid has a muscle that retracts it
- each tarsal plate is connected to the medial and lateral orbital walls by a ligament and to the orbital margin by a thin sheet of connective tissue -> orbital septum
- orbital septum keeps it in place
11
Q
orbicularis oculi
A
- external to the tarsal plate and orbital septum
- arise form the medial tarsal ligament
- sweep laterally in both lids to insert into the lateral tarsal ligament
- closes the eyelid
- muscles fibers near the margin of the lid are employed in blinking
- the remaining fibers are used to voluntarily close the lids
12
Q
levator palpebrae superioris
A
- muscle inserts into the upper margin of the superior tarsal plate
- elevate the lid
- active while the eyes are open
- innervated by oculomotor nerve (CN III)
13
Q
palpebral conjunctiva
A
- lining the eyelids
- continuous with the bulbar conjunctiva over the sclera of the eyeball
14
Q
lacrimal apparatus
A
- consists of a gland that produces tears and the tubes that drain this fluid form the surface of the eye
- lacrimal gland- excretory ducts
15
Q
lacrimal gland
A
- about the size of a an almond
- lies under cover of the superolateral margin of the bony orbit
- has numerous fine excretory ducts that open into the space between the palpebral and bulbar conjunctiva
- lacrimal gland is innervated by the greater petrosal nerve (branch of facial nerve)
- parasympathetic innervation of facial nerve
16
Q
lacrimal punctum
A
- tears from the gland flow across the front of the eye and are collected by a small opening -> lacrimal punctum
- at the medial end of each eyelid
- open into a small tube called the lacrimal canaliculus -> empties into lacrimal sac
- lacrimal punctum -> lacrimal canaliculus -> lacrimal sac -> nasolacrimal duct -> bony nasolacrimal canal -> nasal cavity
17
Q
lacrimal sac
A
- lies in the sulcus formed by the lacrimal bone and maxilla on the inferomedial corner of the orbit
- lacrimal canaliculus drains into lacrimal sac
- drains into the nasolacrimal duct
- nasolacrimal duct runs in the bony nasolacrimal canal -> opens below the inferior concha into the side of the nasal cavity
18
Q
extrinsic eye muscles
A
- 7
- extraocular
- 6 moves the eye
- one elevates the upper eyelid
- at the back of the orbit a tendinous ring spans the optic canal and the middle of the superior orbital fissure
- this common tendinous ring is the origin of 4 of the 6 muscles that move the eye
19
Q
levator palpebrae superioris
A
arises from the lesser wing of the sphenoid bone and runs across the roof of the orbit
- insert into the upper eyelid
- elevates the lid and is continuously active when the eyes open
- innervated by the oculomotor nerve (CN III)
20
Q
muscle that move the eyeball
A
- muscle action- movement in isolation, can be same as function or not
- medial rectus
- lateral rectus
- inferior oblique
- superior rectus
- superior oblique
- inferior rectus
21
Q
medial rectus
A
- arises from the common tendinous ring that runs forward
- insert into the sclera medial to the cornea
- action- move the cornea laterally (abduction)
- function is the same as action
- innervated by oculomotor nerve (CN III)
22
Q
lateral rectus
A
- arises from the common tendinous ring and runs forward
- insert into the sclera lateral to the cornea
- action- move the cornea lateral (abduction)
- function is the same as action
- innervated by abducens nerve (CN VI)
23
Q
inferior oblique
A
- arises from the front of the orbit floor, next to the nasolacrimal fossa
- runs laterally and then turns upward
- insert into the sclera lateral to the cornea
- action is to turn the cornea upward and lateral
- functions when the eye is already adducted to move the cornea upward
- innervated by oculomotor nerve (CN III)
24
Q
superior rectus
A
- arises from the common tendinous ring and runs forward
- insert into the sclera above the cornea
- its action is to turn the cornea upward and medially
- functions when the eyeball is already abducted to move the cornea upward
- innervated by oculomotor nerve (CN III)
25
Q
superior oblique
A
- arises from the sphenoid bone and runs along the orbit roof
- tendon passes through a fibrous pulley (trochlea) attached to the superomedial corner of the orbital rim and then turns backward and laterally
- insert into the sclera above the cornea
- action- to turn the cornea downward and lateral
- functions when the eyeball is already adducted to move the cornea downward
- innervated by the trochlear nerve (CN IV)
26
Q
inferior rectus
A
- arises from the common tendinous ring and runs forward
- insert into the sclera below the cornea
- action is to turn the cornea downward and medially
- functions when the eyeball is already abducted to move the cornea downward
- innervated by the oculomotor nerve (CN III)
27
Q
eyeball
A
- fluid filled structure
- contains light sensitive receptors
28
Q
3 layers of eyeball
A
- outer layer is a thick fibrous tunic -> the muscles that move the eyeball insert into it
- white opaque where it is known as sclera
- anteriorly this layer bulges outward in front of the pupil and becomes transparent cornea
- deep to the fibrous tunic is the thinner vascular choroid -> vascular
- anteriorly choroid layer becomes thickened by smooth muscle (ciliary muscle) to form the ciliary body
- in front of the ciliary body the choroid layer thins and forms the iris -> which contains smooth muscle fibers
- innermost layer is the retina
29
Q
iris
A
- may be pigmented by melanin
- if none is present -> blue
- surrounds an opening known as the pupil
- the muscles that control the size of the pupil are located in the iris
- contain the sphincter (constrictor) pupillae
30
Q
suspensory ligaments
A
- ciliary muscle of the ciliary body gives rise to elastic fibers which are the suspensory ligaments
- they attach to the periphery of the lens
31
Q
retina
A
- light sensitive layer
- surrounded by 2 concentric layers of tissue
- innermost layer of eye
- contains photoreceptors -> rods (black and white shades) and cones (color)
- in the center of the back of the retina is a yellow spot -> macula lutea- cones are concentrated here
- fovea centralis is a depression in the center of the macula lutea that contains cones and no rods
- where the optic nerve exits the eye the retina has no photoreceptors -> called the optic disc (blind spot)
- retina is supplied with blood by the central retinal artery -> runs into the optic nerve to enter the back of eye -> this is a branch of the ophthalmic artery -> comes from the internal carotid artery
32
Q
cavity of eye
A
- divided into 2 parts by lens
- behind the lends is the vitreous chamber -> filled with jellylike substance -> vitreous body
- space in front of the lens is filled with a clear fluid called -> aqueous humor
- this space is divided into two chambers by the iris -> the free margin of which rests upon the lens
- behind the iris is the posterior chamber -> produces aqueous humor and flows through the pupil into the anterior chamber where it is drained by a vein (canal of schelmm) that encircles the cornea
- in front of the iris is the anterior chamber
33
Q
the ear
A
- special sensory information related to hearing and equilibrium (balance)
- 3 regions: external ear, middle ear, inner ear
- all are involved in hearing
- only inner ear is involved in equilibrium
34
Q
external ear
A
- designed to collect sound waves
- lateral to ear drum
- auricle + external acoustic canal
- comprises the auricle and the external auditory (acoustic) canal
35
Q
middle ear
A
- designed to amplify sound waves by turning them into mechanical vibrations
- comprises an air filled tympanic cavity in the temporal bone -> almost completely surrounded by the petrous temporal bone
- tympanic cavity contains 3 bones that transmit vibrations from the outer to the inner ear
- it is bounded laterally by the tympanic membrane
- continuous anteromedially with the auditory (eustachian) tube (usually closed by opens during swallowing and yawning)
- connected posteriorly with the air cells of the mastoid process of the temporal bone
- tympanic cavity is continuous anteromedially with the auditory (eustachian) tube -> opens into the nasopharynx
- bony medial wall of tympanic cavity has 2 small openings: oval and round window -> communicates with inner ear
- middle ear contains the 3 auditory ossicles
36
Q
inner ear
A
- designed to translate mechanical vibrations from the middle ear into nerve impulses that result in hearing
- also translates head posture and movement into neural impulses that relate to the sense of balance
- comprises fluid filled cavities and a series of hollow tubes within the petrous temporal bone -> labyrinth
- bony tubes contain membranous sacs and are filled with fluids
- bony tubes are called the labyrinth bc they are complicated
- vestibulocochlear nerve (CN VIII) transmits information from the labyrinth to the brain
37
Q
tympanic membrane
A
- eardrum
- thin sheet of tissue that is concave laterally and convex medially where it is adherent to the malleus ) an ear ossicle)
- innervated by the auriculotemporal nerve (branch of mandibular division of the trigeminal) and the auricular nerve (branch of vagus)
- continuous with malleus
38
Q
auricle
A
- external ear
- funnels sound waves into the external acoustic meatus (lateral opening of the external auditory (acoustic) canal)
- framework of elastic cartilage
- curved outer rim- helix- originates just above the external auditory meatus and terminates in a fleshy lobe
- antihelix- second curve of auricle -> internal to helix, surrounds a hollow that leads into the external auditory meatus
- tragus- small flap that projects immediately anterior to the meatus
39
Q
external acoustic meatus
A
- auricle funnels sound waves into the external acoustic meatus (lateral opening of the external auditory (acoustic) canal)
- outer half of the external auditory (acoustic) canal is supported by cartilage
- inner half is formed by the temporal bone above and the tympanic bone below
40
Q
bones of middle ear
A
- auditory ossicles: 3 tiny bones
- form a chain from the tympanic membrane to the oval window
- from lateral to medial -> malleus, incus, stapes
- malleus- attached laterally to the tympanic membrane and medially to the incus
- incus is connected to the stapes which communicates with the labyrinth of the inner ear by the oval window
- auditory ossicles form a series of levers that serves to increase the force of sound waves vibrations 20-fold from the tympanic membrane to the oval window
41
Q
muscles of the middle ear
A
- tensor tympani
- stapedius
42
Q
tensor tympani: middle ear muscle
A
increases the tension to dampen the amplitude of vibration if a sound wave that impacts the tympanic membrane is too strong
- runs in a canal through the petrous bone adjacent to the auditory tube, to which it is attached
- inserts on the malleus
- innervated by the mandibular division of the trigeminal nerve (CN V3)
43
Q
stapedius: middle ear muscle
A
- if level of vibration that eventually reaches the stapes is too strong the stapedius dampens its piston-like movement in the oval window
- runs from the mastoid wall of the tympanic cavity
- insert on stapes
- innervated by the facial nerve (CN VII)
44
Q
bony labyrinth: inner ear
A
- cavity within the petrous temporal constitutes bony labyrinth
- filled with a fluid called perilymph
- housed within the bony labyrinth and surrounded by the perilymph are several membranous sacs and tubes that constitute the membranous labyrinth
- membranous labyrinth is filled with a fluid called endolymph
- divides into 3 parts: vestibule, semicircular canals, cochlea
- vestibule and semicircular canals -> equilbrium
- vestibule and cochlea -> hearing
45
Q
bony labyrinth: vestibule
A
- communicates with the footplate of the stapes via the oval window
- within the vestibule are 2 membranous sacs, the utricle and saccule
- static equilibrium
46
Q
bony labyrinth: semicircular canals
A
- dynamic equilibrium
- within the semicircular canals are the semicircular ducts -> continuous with the utricle
47
Q
bony labyrinth: cochlea
A
- communicates with the middle ear via the round window
- contains the cochlear duct (membranous labyrinth)
48
Q
equilibrium: vestibule
A
- static equilibrium
- saccule and utricle
- membranous labyrinth in the vestibule and semicircular canals is concerned with detection of head movement and equilibrium
- within vestibule -> 2 membranous sacs -> utricle and saccule -> concerned with maintenance of static equilibrium (head position) and detection of head tilting in the sagittal plane (acceleration or deceleration for ex.)
- utricle is the larger and more important
- each has a receptor region -> macula
- within the macula sensitive hair cells are embedded in a jelly-like otolithic membrane
- calcium carbonate crystals known as otoliths rest on this membrane
- otoliths press against hair when you tilt head -> register that your head is moving
49
Q
equilibrium: semicircular canals
A
- dynamic equilibrium
- emerging from the utricle are 3 membranous semicircular ducts contained within the bony semicircular canal
- they are concerned with the detection of dynamic equilibrium
- canals occupy different planes
- anterior canal: sagittal plane
- posterior canal: coronal plane
- lateral canal: horizontal plane
- near their origins at the utricle each semicircular ducts is enlarged to form an ampulla -> contains sensitive hair cells embedded is a mass of gelatinous material called the cupula
- rotation of head
- fluid presses against cupula and receptors tell the brain your body is going through a change in dynamic equilibrium
50
Q
oval window
A
-vestibule communicates with the middle ear via the oval window which houses the footplate of the stapes
51
Q
endolymphatic duct
A
- extending from the utricle and saccule is an accessory endolymphatic duct
- runs posteromedially through the petrous bone to emerge on its posterior surface under cover of the dura mater
- end of duct is known as the endolymphatic sac -> no function
52
Q
hearing: cochlea
A
- part of bony labyrinth
- coiled tube
- filled with perilymph
- housed within the cochlea is a membranous labyrinth tube known as the cochlear duct aka scala media -> filled with endolymph -> triangular cross section
- bony cochlea has a spur of bone that projects into the cochlear tube along its entire length
- this spur joins the apex of the triangular membranous duct -> divides the bony labyrinth into 2 parts: scala vestibuli and scala tympani
- at the apex of the cochlea the scala vestibuli and scala tympani are continuous with one another through a small opening known as the helicotrema
- within the cochlear duct is a sheet of hair cells that are the receptors for auditory sensations
- these cells form the spiral organ of corti -> lies against the basilar membrane
- tectorial membrane- projects over the hair cells as a tent (gelatinous)
- fluxuation of the lymph is translated into hearing bc of organ of corti -> cochlear branch of vestibulocochlear branch
53
Q
hearing: cochlea: scala vestibuli
A
- open to the vestibule at one end
- membranous sheet that separates the perilymph of the scala vestibuli from the endolymph of the cochlear duct is known as the vestibular membrane
54
Q
hearing: cochlea: scala tympani
A
- communicates at one end with the middle ear cavity via the round window
- round window is covered with a thin membrane
- membranous sheet that separates the perilymph of the scala tympani from the endolymph of the cochlear duct is known as the basilar membrane
55
Q
palpebral fissure
A
-elliptical opening between the palpebrae (eyelids)
56
Q
lacrimal apparatus path
A
-tears produced in lacrimal gland -> excretory ducts -> external surface of eye -> medial campus -> lacrimal punctum -> lacrimal canaliculus -> lacrimal sac -> nasolacrimal duct -> nasolacrimal canal ->
57
Q
adduction
A
- looking medially (towards nose)
- medial rectus
58
Q
abduction
A
- looking laterally
- lateral rectus
59
Q
elevation
A
- looking up
- superior rectus
- inferior oblique
60
Q
depression
A
- looking down
- inferior recuts
- superior oblique
61
Q
adduction and elevation/depression
A
- medial rectus and inferior oblique -> medial elevation
- medial recuts and superior oblique -> medial depression
62
Q
abduction and elevation/depression
A
- lateral rectus and superior rectus -> lateral elevation
- lateral rectus and inferior rectus -> lateral depression
63
Q
oval window
A
-continuation that opens to the inner ear
64
Q
rectus muscles
A
-originate at the common tendinous ring
