Section 4

Question 1

The ear is divided into three sections:

Answer 1

• inner ear
• middle ear
• external ear

Question 2

Describe briefly the external ear

Answer 2

• represents the structure of the ear you can touch
• sound waves from the environment travel through the external auditory canal to reach the tympanic membrane, causing it to vibrate
• ceruminous glands are microscopic and secrete ear wax

Question 3

What is the tympanic membrane?

Answer 3

• AKA the eardrum
• marks the boundary between the external and middle ear
• transmits sound from the external environment to the ossicles of the middle ear

Question 4

What impact is the perforated tympanic membrane likely to have on hearing?

Answer 4

• The effect is decreased or disrupted hearing

Question 5

Briefly describe the middle ear

Answer 5

• located within the temporal lobe
• spans from the tympanic membrane to the oval window
• sound waves involved with hearing are also transmitted through the middle ear

Question 6

Describe the parts of the middle ear

Answer 6

• Ossicles: small bones located in the middle ear
• Tympanic cavity: chamber in the temporal bone
• Round and oval windows: Areas at which the middle ear connects to the inner ear
• Eustachian tube: Connects the middle ear to the nasopharynx

Question 7

What are the ossicles, and what muscles are attaches to them?

Answer 7

• The ossicles are three small bones located in the middle ear
• they help transmit sound waves to the receptors in the inner ear
• the muscles attached to the ossicles (the tensor tympani and the stapedius) function to dampen very loud noises

Question 8

What are the three ossicles?

Answer 8

• Malleus (hammer): the most lateral ossicle that is attached to and behind the tympanic membrane
  -Incus (anvil): sits between the malleus and the stapes
• Stapes (stirrup): the smallest bone and sits in the oval window. It is about 1/3 the mass of the other ossicles. (also looks like a stirrup)

Question 9

What are the labyrinths, and where are they?

Answer 9

• Both the cochlea and vestibular apparatus are structured as two channels in the bone, called labyrinths (the membranous and bony labyrinths)
• the membranous labyrinth is within the bony labyrinth
• both labyrinths are filled with fluids that allow us to hear (cochlea) or become aware of and monitor the position of our head (vestibular apparatus)
• the membranous labyrinth is filled with endolymph and the bony labyrinth is filled with perilymph

Question 10

What is the vestibular apparatus and what is it composed of?

Answer 10

• The vestibular apparatus contains the receptors for equilibrium
• Composed of three structures:
  1. semicircular canals: detect rotational movement (head moving up and down, side to side and tilting)
  2. utricle
  3. saccule: detect positional movement (head moving from one point in space to another, with respect to gravity and linear acceleration)

Question 11

What is the cochlea and what is it composed of?

Answer 11

• contains the receptors for hearing
• composed of three ducts: the vestibular duct, the tympanic duct, and the cochlear duct

Question 12

Describe the organs of Corti

Answer 12

• A specialized structure integral to hearing
• Found in the cochlear duct of the cochlea
• made up of specialized cochlear hair cells that rest on a basilar membrane
• when the membrane is moved by sound waves, the hair cells fire an impulse, which is sent to the brain via CN VIII for interpretation