Ears

Question 1

External ear

Answer 1

Consists of the:
- Auricle (pinna)
- External acoustic meatus (Auditory canal)
- Hairs
- Sebaceous and ceruminous glands

Question 2

Tympanic membrane

Answer 2

• Also known as the eardrum
• Thin connective tissue membrane that transfers sound energy to the auditory ossicles
• Separate the outer and middle ear

Question 3

Middle ear

Answer 3

• Also known as the tympanic cavity
• Small air-filled, mucosa-lined cavity in the temporal bone spanned by the auditory ossicles

Question 4

Auditory ossicles

Answer 4

• Malleus
• Incus
• Stapes

Question 5

Pharyngotympanic tube

Answer 5

• Also called the Eustachian tube
• links the middle ear with the nasopharynx allowing pressure to be equal between the middle and external ear

Question 6

Inner ear

Answer 6

A bony labyrinth is a series of channels carved into the temporal bone including the:
- Scala vestibuli
- Scala tympani
- Filled with perilymph (similar to CSF)

Question 7

Membranous labyrinth

Answer 7

Made up of membranous ducts within the bony labyrinth such as the scala media
Filled with endolymph (contains more K+ than perilymph)

Question 8

Cochlea

Answer 8

• Spiral and snail-shaped
• Extends from the anterior part of the vestibule and contains the cochlear duct which houses the spiral organ (Organ of Corti), the receptor organ used for hearing

Question 9

Three chambers of the bony cochlea

Answer 9

• Scala vestibuli: (next to the oval window)
• Scala media: Cochlear duct
• Scala tympani: terminates the round window
• Basilar membrane: the door of the cochlear duct that is important for sound reception

Question 10

Organ of Corti

Answer 10

These are hair cells that detect vibrations between he basilar membrane and the tectorial membrane

Question 11

Sound

Answer 11

Produced by a vibrating object and propagated by the molecules of the medium

Question 12

Frequency

Answer 12

• Number of waves that pass a given point in a given time
• Measured in Hertz (Hz)
• Low frequency = long wavelength and high frequency = short wavelength

Question 13

Amplitude (height)

Answer 13

• Reveals a sound’s intensity (loudness) in a wave
• Measured in decibels (dB)

Question 14

Sound transmission

Answer 14

• Sound enters the auditory canal, causing the eardrum to vibrate
• Vibrations go from the ossicles to the oval window on the vestibule (amplified about 20-fold), producing a pressure wave within the perilymph

Question 15

Resonance

Answer 15

• This is tuned to specific frequencies on the basilar membrane
  In the cochlea:
• Fibres close to the oval window are short and stiff and respond to high frequencies
• Fibres close to the apex resonate with low frequencies