1.3 Special Sense Organs (Ear)

Question 1

What are the 3 distinct regions of the ear and their jobs:

Answer 1

External: sound collection​
Middle: sound transmission
Inner: sound reception / Vestibular (balance center

Question 2

What makes up the exte​rnal ear:

Answer 2

Pinna and external canal:

Pinna collects sound & funnels it into the external canal ending at the ​tympanic membrane

Question 3

What makes up the Middle ear:

Answer 3

The 3 ossicles / bones transmit vibrations across tymp​anic membrane

Question 4

What does the Tympanic membrane divide?

Answer 4

middle and outer ear

Question 5

helps equalize pressure in middle ear

Answer 5

eustachian tube

Question 6

What makes up the Inner ear:

Answer 6

Membranous labyrinth​ of fluid chambers (cells can detect sound waves here)

Question 7

What is the vestibular complex made up of?

Answer 7

• saccules
• Utricules
• 3 semi-circular canals

Question 8

Explain what this diagram is showing Part 1 of 4:

Answer 8

• Before neuro plate closure, the surface ectoderm is induced to thicken
• This thickening is the Auditory Placode

Question 9

Explain what this diagram is showing Part 2 of 4:

Answer 9

The auditory placode deepens and invaginates to form the ​auditory pit

Question 10

Explain what this diagram is showing Part 3 of 4:

Answer 10

• Auditory pit continues to fold in until the area of ectoderm separates from the surface by ‘pinching off ‘
• This now forms and becomes the auditory vesicle​

Question 11

Explain what this diagram is showing Part 4 of 4:

Answer 11

The Auditory vesicle induces the surrounding mesenchyme to form the cartilaginous ear capsule

Question 12

Differentiation of Auditory vesicle to form inner ear Part 1:

Answer 12

Dorso-ventral extension (elongation) of the Auditory Vesicle

Question 13

Differentiation of Auditory vesicle to form inner ear Part 2:

Answer 13

• Finally, the ‘body’ of the ​auditory vesicle is subdivided
• Forms Utricle and Saccule

Question 14

The utricle and saccule are important for?

Answer 14

linear movement

Question 15

External Ear development:

Answer 15

*Within the mesenchyme of the 1st visceral cleft (between the 1st VA and the hyoid arch) focal condensations appear

*These condensations each produce a nodular enlargement either side of the cleft

*Nodular enlargements coalesce and form primordium of the pinna

*Modified by differential outgrowth.

Question 16

Scutiform Cartilage characteristics​:

Answer 16

• Has a boot-like structure
• L shapes before the ​tympanic membrane
• animals get things stuck in here due to horizontal position

Question 17

cochlea function & how it detects sound to send to medulla

Answer 17

1) external sound waves travel through external auditory meatus hitting tympanic membrane
2) tympanic vibrates oval window transfering vibrations to ossicles
2) ossicles amplify sound shifting tectorial &basilar membranes against cochlear endolymph hair cells
3) Hair cells displace& bend stimulating organ of corti hair cells to covert sound vibrations into nerve impulses
4) CN VIII sends impulses to brain

Question 18

An indication​ that a hematomia has formed near auricular cartilage?

Answer 18

IF:
- hot
- swollen
- painful
- blood

Question 19

Where does the blood supply come from for the outer ear?

Answer 19

Most of the supply will​ come from carotid blood vessels and eventually go through ear

Question 20

what is the bony labyrinth?

Answer 20

vestibule as central chamber, semicircular canals, cochlea all with portion of membranous labyrinth inside them

Question 21

What could damage to the Chondra tympani cause? What nerve branch is this?

Answer 21

Could cause lose of sensation to 2/3 of the tongue
- Branch of VII

Question 22

cochlea function &how it detects sound to send to medulla

Answer 22

1) external sound waves travel through external auditory meatus hitting tympanic membrane
2) tympanic vibrates oval window transfering vibrations to ossicles
2) ossicles amplify sound shifting tectorial &basilar membranes against cochlear endolymph hair cells
3) Hair cells displace& bend stimulating organ of corti hair cells to covert sound vibrations into nerve impulses
4) CN VIII sends impulses to brain

Question 23

inner hair cells:

Answer 23

• 10- 25% of the cells with 90% of the innervation.
• Responsible for sound transmission converting sound mechanical energy to electrochemical signals.
• Not replaced hence can lead to deafness.
• fewer

Question 24

outer hair​​ cells:

Answer 24

-75-90% of cells with 10% of the innervation.
- Responsible to for somatic electromotility - amplification of the incoming sound waves. The cells can change length leading to amplification feedback.

Question 25

Hearing - the hair cell receptor

Answer 25

*Hair cells discharge in relation to the excursion of the basilar membrane
*The tips of the cilia are project c​lose to the tectorial membrane and so are flexed by sound vibrations
*Each cilium contains mechanically-gated non-selective cation channels. K+ is the main cation in endolymph

Question 26

condution causes of deafness

Answer 26

Blockage of sound transmission via:
- Otitis
- Wax
- Tumors
- tympanic rupture

Question 27

Which area do low frequencies stimulate on cochlea and why?

Answer 27

cochlea apex/top with narrow tip &is more flexible, loose & wider

Question 28

which area do high frequencies stimulate on cochlea & why?

Answer 28

cochlea base/ opening near oval window thats more stiff & narrow

Question 29

nerve causes of deafness

Answer 29

• congenital/genetic
  ex: (white cats with blue eyes, dalmatians)
• age: hair starts to die
• aminoglycoside antibiotics

Question 30

function of semi- circular canals

Answer 30

head rotates causing endolymph to flow through corresponding canal displacing cupula &bending hair cells in opposite directions innervating CN VIII

Question 31

what does post​erior semicircular canal detect?

Answer 31

head tilting

Question 32

what does Anterior semicircular canal detect?

Answer 32

head moving forwards & backwards (nodding)

Question 33

what does the lateral/horizontal semicircular canal detect?

Answer 33

horizontal head movement, control balance

Question 34

maculae control?

Answer 34

linear movement​ / acceleration

Question 35

components of vestibular complex, their orientation &trigger plane of movement

Answer 35

1) Saccular macule: vertical so vertical movements trigger
2) utricular macule: horizontal so horizontal movements trigger

Question 36

Explain macule role in linear acceleration

Answer 36

Head tilts cause gravity to shift otolithic membrane over sacculus relative to sensory epithelium displacing hair bundles in macula triggering impulses via CN VIII

Question 37

Unilateral vestibular signs:

Answer 37

Question 38

What do semicircular​ canals control?

Answer 38

balance