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ANP 300 > Lab 8: Eye and Ear > Flashcards

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
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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
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3
Q

sclera

A
  • white of the eyeball

- covered by transparent bulbar conjunctiva

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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
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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
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6
Q

optic canal

A
  • pierces the lesser wing of the sphenoid

- conveys the optic nerve

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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
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8
Q

thin inferior orbital fissure

A

-a thin inferior orbital fissure separates the sphenoid and maxilla

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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
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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
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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
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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)
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13
Q

palpebral conjunctiva

A
  • lining the eyelids

- continuous with the bulbar conjunctiva over the sclera of the eyeball

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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
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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
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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
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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
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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
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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)
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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
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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)
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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)
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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)
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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)
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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)
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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

ANP 300 (20 decks)

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