Exam 2 Flashcards
What is an otoscope?
A handheld device w/ a light used for looking through the ear canal or nose.

What is the role of the eustachian tube?
Equalizes pressure so that the pressure behind the eardrum equals the pressure in front of it. (Auditory tube in picture)

Medial wall of the middle ear
- AKA Labyrinthine Wall
- Deep inside the ear; inner ear behind it
- Oval & round windows
- communicate w/ cochlea
- Pic: fenestra cochlea = round window; fenestra vestibuli = oval window

Lateral wall of the middle ear
- AKA tympanic wall
- Formed by the tympanic membrane
- First thing an audiologist would see when looking into the ear

Superior wall of the middle ear
- AKA tegmental wall
- Formed by a thin layer of bone, the tegmen tympani
- Roof of the cavity
- Separates middle ear cavity from cranial cavity
- Infection that spreads through superior wall causes meningitis.

Inferior wall of the middle ear
- Formed by the fundus tympani, a thin bony plate
- Lies above the jugular fossa (hole where the jugular bulb goes in) w/ the jugular bulb (holds jugular vein)

Anterior wall of the middle ear
- AKA carotid wall
- Connects to the back of the throat through the eustachian tube
- Contains the internal carotid artery (goes through carotid canal close to the anterior wall)

Posterior wall of the middle ear
Communicates with mastoid air cells through an opening, the aditus

Tympanic membrane: position & size
- Held in a groove called the tympanic sulcus
- Inclined at 55º angle
- Total area: 85 mm2
- Active area: 55 mm2

Tympanic membrane: layers
- Outer: epithelial, like our skin. Continuous w/ the ear canal skin
- Middle: fibrotic. Fibrous bridge between epithelial & mucosal. Gives the membrane flexibility, allowing it to move. Inactive portion lacks this.
- Inner mucosal: lining of nose continous with the back of the throat & eustachian tube. Secretes mucous when it’s stimulated
Tympanic membrane: Pars Tensa
Active portion of the tympanic membrane (55 mm2)

Tympanic membrane: Pars Flaccida
- AKA Sharpnell’s Membrane
- Inactive portion of the tympanic membrane (remaining 30 mm2)

Tympanic membrane: Cone of light
Reflection of light from the umbo to the lower surface of the eardrum that shows up when viewing eardrum through otoscope (inferior-anterior).

Tympanic membrane: Chorda Tympani Nerve
- Branch of facial nerve (7th)
- Sensory: supplies anterior 1/3 of tongue
- Motor: supplies muscles of facial expression
Tympanic membrane: umbo
Point of maximum retraction of the TM where the handle of the malleus attaches.

Middle ear ossicles
- Malleus, incus & stapes
- Serially connected
- Form an ossicular chain
- Suspended by 6 ligaments
- Handle of malleus attached to TM

Malleus
- AKA hammer
- Manubrium = handle
- (Blue arrow indicates umbo)
- 25 mg

Incus
- AKA anvil
- 25 mg

Stapes
- AKA stirrup
- Footplate rests on oval window of medial wall
- 2.5 mg (smallest bone in the body)

Area of tympanic membrane vs. oval window
- TM (active area) is 55 mm2
- Oval window is 3.2 mm2
- TM is 17x larger
- translates to functional gains
Ligaments of the malleus
- 3 ligaments:
- Superior: attaches to head
- Lateral: attaches to neck
- Anterior: attaches to anterior (lateral) process

Ligaments of the incus
- 2 ligaments:
- superior: attaches to body
- posterior: attaches to short process

Ligaments of the stapedius
Annular ligament: holds footplate onto oval window

Tensor tympani
- Attached to the handle of the malleus
- Held by semicanal for tensor tympani on medial wall
- Innervated by the trigeminal nerve (5th)
- Reflex contraction to loud sounds
- Increases tension of TM for sounds of 85-90 dB SPL or greater and < 1000 Hz

















