Ear

Question 1

fnctn

Answer 1

maintains balance (vestibular), perceives sound (auditory)

Question 2

parts of ear

Answer 2

mexternal (to tymp mem), middle, and inner (in petrous ridge of temp bone)

Question 3

external ear

Answer 3

-external acoustic meatus, tymp mem, and auricle gather sound and direct it to tymp mem

Question 4

how does cone of light project

Answer 4

anteriorly

Question 5

embryologic origins of tmyp mem

Answer 5

1st pharyngeal pouch (endoderm) and groove (ectoderm)

Question 6

fnctn of middle ear

Answer 6

transmits sound vibrations from tymp mem to inner ear via ossicles

Question 7

middle ear cavity

Answer 7

• tymp cavity:air spac in temp bone
• tymp cavity proper: medial to tymp mem
• epitympanic recess: sup to tymp mem and ossicles
• anteriorly: leads to auditory tube and nasopharynx
• posteriorly: aditus and antrum

Question 8

aditus

Answer 8

doorway into mastoid antrum and air cells, continuous with mastoid antrum and auditory tube

Question 9

auditory tube

Answer 9

• has bone and cart (sup and mid walls ant 2/3) parts
• inf and lat walls are mem

*tensing of tensor veli palatini opens tube

Question 10

middle ear boundaries

Answer 10

roof: tegmen tympani (bony)
floor: jugular wall-thin layer of bone separating cavity ad IJV
lat: tymp mem-attaches to manubrium of malleus
med: tymp cavity, inner ear labyrinth
ant: carotid wall-thin bone separating mid ear cavity and carotid canal
post: mastoid wall

Question 11

features in medial wall of middle ear

Answer 11

• promentory: from cochlea, facing tymp mem, covered by tymp plexus
• fenestra vestibuli: oval window, receives base of stpaes
• fenestra cochlea: round window, mem covered, inf to oval
• facial canal prom: CN VII inside
• lat semicirc canal prom

Question 12

openings in sup part of ant wall of mid ear

Answer 12

1. auditory tube

2. semicanal for tensor tymp m

Question 13

features of post wall of mid ear

Answer 13

1. pyramidal eminence: hollow bone, origin of stapedius m

2. aditus ad antrum: entrace to tymp antrum

Question 14

ossicles

Answer 14

• malleus, incus, stapes
• lined with simple squamous epi
• malleus and incus articulate
• incus and stapes articulate
• stapes attaches to tymp mem via oval window

Question 15

mm of middle ear

Answer 15

1. tensor tympani: in bony semicanal, insets onto handle of malleus, teses tymp mem, inn by CN V3 (from arch I)
2. stapedius: arise from cav inside pyramidal eminence
   - inserts into neck of stapes
   - inn by CN VII (from arch II)

Question 16

vessels of mid ear

Answer 16

• arterial supply via tymp brs of caroitd brs (ant tymp a from max a)
• accompanying vv (to sup petrosal sinus-intracranially, to pterygoid plexus of vv-extracranially)

Question 17

path of facial n and canal, and chorda tympani

Answer 17

• CN VII enters canal posteriorly and runs ant
• travels in medial wall of mid ear
• exits and stylomastoid foramen
• CN VII turns ar geniculate gang
• chorda tymp (ascends ant thru mid ear) comes off CN VII joins ling for special sensory of ant 2/3 tongue

Question 18

greater petrosal n

Answer 18

• br off geniculate gang of CN VII
• carries parasymp fibers to pterygopalatine gang
• joins deep petrosal n (symp) to make n or pterygoid canal

Question 19

tympanic plexxus of nn

Answer 19

• covers promentory, runs under mucosal lining, and supplies it
• formed by tymp br of CN IX (parasymp) and cartoticotympanic n (symp)

Question 20

lesser petrosal n

Answer 20

• br of tympanic plexus of nn
• continuation of tymp br of CN IX
• carries parasymp to otic gang (sits outside of foramen ovale, by CN V3)

Question 21

inner ear

Answer 21

• fluid filled chamber for hearing and equilibrium
• semicirc canals: controls balance and position
• cochlea: controls hearing
• oval window: beginning of transduction of sound (cochlea)
• round window: end of transduction of sound, vibrates –opposite oval window to perceive sound
• membraneous structures: semicirc canals, utricle and saccule

Question 22

transmission of sound

Answer 22

-waves are established in perilymph, cause vibration of basilar mem of spiral gang of corti