The Ear

Question 1

3 main sections of the ear

Answer 1

outer
middle
inner

Question 2

outer ear

Answer 2

pinna
external auditory meatus (EAM - ear canal)
tympanic membrane (ear drum)

Question 3

function of outer ear

Answer 3

collect and funnal sound into skull towards inner ear

Question 4

role of tympanic membrane

Answer 4

boundary between external and middle ear
○ Collection vibrations and pressure waves down the EAM and the TM vibrates and transfers them to middle ear

Question 5

shape of EAM

Answer 5

sigmoid shaped and not straight

Question 6

division of tympanic membrane

Answer 6

• Subdivided into anterior and posterior or superior and inferior
  
  • Quarters:
    ○ ASQ - anterior superior
    ○ AIQ - anterior inferior
    ○ PSQ - posterior superior
    ○ PIQ - posterior inferior

Question 7

parts of the tympanic membrane

Answer 7

handle of malleous (short process of malleous at top)

pars flaccida at top of membrane

pars tensa is around the handle of malleous

Question 8

middle ear

Answer 8

empty cavity sitting in the temporal bone

Question 9

middle ear connection to outside world

Answer 9

via a small Eustachian tube that enters the nasal canal cavity

Question 10

ossicles (bones) in the inner ear

Answer 10

malleus
incus
stapes

descending size from lateral to medial

Question 11

role of ossicles

Answer 11

transmit vibration from the tympanic membrane to the sensitive inner ear via an oval window

Question 12

role of middle ear

Answer 12

amplifying vibrations of tympanic membrane

impedance matching the vibration of air and liquid (from the outside world to fluid inside the inner ear)

Question 13

nerve transversing middle ear

Answer 13

facial nerve

Question 14

Tensor tympani

Answer 14

attaches to malleus and dampens very loud sounds

Question 15

Stapedius muscle

Answer 15

(1mm long)
○ Dampens and limits the vibrations/movements of stapes
○ Nerve to stapedius is literally called ‘nerve to stapedius’
○ Branch of facial nerve (7)
○ If nerve to stapedius is damaged e.g. in Bell’s palsy and the stapedius muslce doesn’t work then normal sounds will seem so loud

Question 16

where is the inner ear

Answer 16

petrous part of temporal bone

Question 17

role of inner ear

Answer 17

transduce vibration/sound into electrical activity or AP and to provide balance

Question 18

2 parts/layers of labyrinth

Answer 18

bony and membranous labyrinth

Question 19

fluid in the membranous labyrinth and its function

Answer 19

endolymph fluid - bathes the whole of the sensory epithelium inside the inner ear

Question 20

fluid between the bony and membranous labyrinth

Answer 20

perilymph

Question 21

where are endolymph and perilymph fluids

Answer 21

endolymph - in membranous labyrinth

perilymph - between bony and membranous labyrinth

Question 22

2 functional parts of the inner ear

Answer 22

cochlear - hearing
vestibular system - balance

Question 23

nerve wired to the special sensory organs of hearing and balance

Answer 23

vestibulocochlear nerve (CNVIII)

Question 24

vestibular system is responsible for…

Answer 24

balance

Question 25

vestibular system consists of...

Answer 25

2 sacs called the utricle and sacculle 3 semi-circular canals (horizontal, posterior, superior)

Question 26

what is at the end of the semicircular canals

Answer 26

swellings called ampulla

Question 27

where is the oval window

Answer 27

under stapes

Question 28

flow around the cochlear

Answer 28

- Scala vestibular (vestibular duct) ○ Carries vibrations to tip of cochlea - Scala tympani (deep to the bone) ○ Carries vibrations back to the round window

Question 29

role of endolymph in cochlear duct

Answer 29

in the cochlea duct - Lots of potassium ions so AP triggered well - If mixed with perilymph then the concentration of potassium ions lost and hearing effected.

Question 30

role of utricle

Answer 30

(detects horizontal movements) § Contains a macula

Question 31

role of sacculle

Answer 31

(detect vertical movements) § Contains a macula

Question 32

sensory organ of vestibular system

Answer 32

hair cell

Question 33

clusters of hair cells form...

Answer 33

modified sensory epithelium floating in the endolymph

Question 34

structure of hair cells in the vestibular system

Answer 34

clusters of hair cells form modified sensory epithelium floating in the endolymph each hair cell is connected to vestibular neuron consisting of a body and stereocilia projecting outwards (longest one is kinocilium) (encased in gel)

Question 35

hair cells are constantly doing what?

Answer 35

firing AP down their vestibular neurons towards the brain

Question 36

hair cells are found where?

Answer 36

in macula in utricle and sacculle

Question 37

what is special about the hair cells in the macula?

Answer 37

otoconia (crystals) on top of the gel layer that add inertia to the system and emphasise movements.

Question 38

direction of macula in utricle

Answer 38

dangle from roof

Question 39

role of macula in utricle

Answer 39

detect linear or horizontal acceleration

Question 40

direction of macula in sacculle

Answer 40

hang from wall

Question 41

role of macula in sacculle

Answer 41

detect vertical acceleration

Question 42

hair cells in the semicircular canals

Answer 42

cup shaped layer called cupula sensory epithelium called crista no otoconia

Question 43

role of crista

Answer 43

detect angular acceleration but only in the same plane as the movement

Question 44

when is horizontal canal stimulated

Answer 44

when you look left or right

Question 45

when is superior canal stimulated

Answer 45

when you look up or down

Question 46

when is posterior canal stimulated

Answer 46

lookup as laid down

Question 47

majority of info provided by semicircular canals is destined to go where?

Answer 47

extraocular eye muscles

Question 48

how does the majority of info provided by semicircular canals is destined to go to the extraocular eye muscles?

Answer 48

achieved in the brainstem by relays from the vestibular nuclei to the nuclei of CN3, 4 and 6.

Question 49

vestibulo-ocular reflex (VOR)

Answer 49

keep the vision and gaze fixed on the object despite the head, body or object moving.

Question 50

transduction of sound is conducted by what?

Answer 50

hair cells in the cochlear

Question 51

blood supply to the ear

Answer 51

○ Posterior and anterior to the EAM ○ Posterior auricular artery supplies posterior part of the ear ○ Anterior part (anterior to EAM) is supplied by superficial temporal artery ○ Both branches of external carotid artery ○ Posterior part of ear is innervated by branches from spinal level c2 and c3 and cervical plexus ○ Anterior ear is innervated by trigeminal nerve (3rd branch - mandibular branch), vagus and facial nerve