Download The Ear

The Ear
Marlene Arceo
Leonardo Cabrera
Isaac Brabb
Melanie Weyers
General functions of the ear
1. Two Main Functions:
i.
ii.
Assist with balance of individual
Collect sounds and relay them to the brain
Outer ear
1. Structure:
i. Made of tough cartilage covered by skin
ii. Contains external acoustic meatus
a) Secrets cerumen (protects ear canal)
b) Guarded by hair
c) Ends at the tympanic membrane (eardrum)
Outer ear (Cont.)
1. Function:
i.
ii.
Auricle
a)
Collects sound waves travelling through air
b)
Directs sound waves into external acoustic meatus
c)
Sound waves travel through tube all the way to the
tympanic membrane
Tympanic Membrane
a)
Semitransparent membrane covered by thin layer of skin
on outside / mucous on inside
b)
Oval margin / cone shaped
c)
Moves back and forth in response to sound waves
d)
Whatever sound wave enters the canal becomes processed
and moves on to middle ear
Middle ear
-An air-filled,
membrane lined
space internal to the
eardrum/tympanic
membrane and
external to the oval
window of the
cochlea
-couples sound from
air to the fluid via the
oval window
Middle earEustachian Tube
• Links the nasopharynx to the middle ear
• Remains closed under normal conditions
1. Pressure Equalization
a)
When pressure inside middle ear is
different form pressure of atmosphere,
the tube can be opened from yawning,
swallowing, or chewing because it lets
small amounts of air and equalizes the
pressures
2. Mucus Drainage
a)
Eustachian tube allows fluid/mucus to
drain out of the ear.
Middle Ear-OSSICLES
1. 3 small, movable bones
• Vibrate when the eardrum/tympanic
membrane vibrates from sound waves
entering the ear canal
a)
Hammer (malleus)
i.
ii.
b)
Anvil (incus)
i.
c)
Bone connected to inside of the
tympanic membrane and to the
incus/anvil
Transmits sound vibrations to the
incus
Second bone connected to hammer
to the stapes
Stirrup (stapes)
i.
ii.
The third U-shaped bone connected
to the stirrup and to cochlea
Smallest bone in the body
Muslces
• Tympanic/Acoustic Reflex: muslces contract in
response to loud sounds, thereby reducing the
transmission of sound to the inner ear
• Stapedius muscle-(smallest skeletal muscle in the body)
connects to the stapes and is controlled by the facial
nerve
• Stapetensor tympanic muscle-connects to the base of
the malleus and is under the control of the medial
pterygoid nerve
Nerves
• horizontal and chorda tympani branches of the facial
nerve pass through the middle ear space
• Damage to the horizontal branch during surgery can
lead to partial mastoid process paralysis
Inner Ear (video)
Inner Ear
1. Location:
a) Within temporal bone
2. Functions:
a) Hearing and balance
3. Structures:
a) “Bony Labyrinth”
b) “Membranous
Labyrinth”
c) Round Window
d) Eighth Cranial Nerve
e) Contains perilymph and
Endolymph Fluid
Bony vs. Membranous
Labyrinth
1. Bony Labyrinth
2. Membranous Labyrinth
a) Ducts created by the grooves and
channels in the temporal bone
b) Larger
c) Contains Perilymph
d) Ex: Outer Tire of a Bike
a) Located INSIDE of the Bony
Labyrinth
b) Smaller
c) Contains Endolymph
d) Ex: Inner tube of Bike Tire
Perilymph vs. Endolymph
Fluid
1. Perilymph Fluid
a) Similar composition
to CSF
b) Rich in Sodium
c) Located in Bony
Labyrinth
d) Shock buffer
e) Helps transmit waves
to membranous
labyrinth
2. Endolymph Fluid
a) Where actual perception of
balance, equilibrium, and sound
take place
b) Rich in Potassium
c) Located in Membranous
Labyrinth
Cochlea
1. Snail like structure for hearing
2. Converts sounds and vibrations from the external
environment into electrical impulses
3. Transduction
i.
When vibrations are made into impulses able to be
interpreted by the brain
ii. Vibrations stimulate oval window, causes the fluid to move
through cochlea to the Organ of Corti
a) Sensory nerve “hair-like” receptors in the cochlea
4. Sensory cells in the cochlea perform transduction and the
electrical impulse travels to the brain via Cochlear nerve
Cochlea
Semicircular Canals
1. Mainly for balance and steadiness
2. Contains Perilymph and Endolymph
3. When the body (especially the head) changes
position, endolymph moves, hair cells in the canal
sense the movement and relay the information to the
brain.
a)
Helps sense movement of the body and maintain balance
Semicircular Canals
Vestibule
1. Regulates balance and equilibrium
a) Connects the semicircular valves and the cochlea
2. Also contains hair cells that sense changes in the waves and
flow of Endolymph fluid to help maintain balance
3. Vestibular nerve relays information to regulate balance and
equilibrium
a) Does not require conscience changes from the cerebrum
b) The body will automatically adjust itself
4. These help detect Lateral/Horizontal movement
a) Saccule: Inferior Portion of Vestibule
b) Utricle: Superior Portion of Vestibule
Vestibule
Round Window
1. Location:
a) Inner ear between the
middle ear and the cochlea
2. Senses vibrations from
middle ear, then indents
into the inner ear to
stimulate waves and
movement of perilymph
fluid.
3. Release to decrease
pressure within the ear
Static equilibrium
1.
Organs involved are located within utricle and saccule
2.
Utricle and saccule contain hair cells that project vertically or horizontally
depending between utricle and saccule
3.
Hair contacts sheet of gelatinous material that ahs calcium carbonate crystals
embedded
4.
The hair cells have nerve fibers wrapped around their bases
5.
Gravity stimulates hair cells to respond (i.e. bending head)
6.
Gelatinous material sags in response to gravity
7.
Stimulates hair cells, signal associated nerve fibers
8.
Nerve impulses travel to the CNS
9.
Informs brain of head’s position
10. Brain responds bye sending motor impulses to skeletal muscles which maintain
balance
Static equilibrium
Dynamic equilibrium
1.
3 semicircular canals that are responsible for detecting changes
in motion.
2.
In each canal there is an ampulla
3.
Communicates with utricle
4.
Contains sensory organ crista ampullaris
5.
Also contains sensory hair cells
6.
When the head or torso moves, the semicircular canals move as
well
7.
This causes the hairs to bend, stimulating associated nerve fibers
and as a result impulses travel to the brain.
Dynamic equilibrium
Ménière’s Disease
• Disease of the inner ear that causes vertigo (severe dizziness),
ringing in the ears, hearing loss, and feeling of congestion in the
ear.
• Usually affects only one ear
• Symptoms can be caused by:
1.
2.
The buildup of fluid in compartments of the ear (labyrinth)
It interferes with the normal balance and hearing signals between the
inner ear and the brain
• How is it diagnosed:
1.
2.
3.
Medication to treat dizziness
Limit salt in diet / taking diuretics
Inject antibiotics (gentamicin) into the middle ear
Ménière’s Disease
Otitis
•
General term for infection or inflammation of the ear.
•
Classified according to whether it occurs suddenly for a short time or repeatedly over a long period of time
•
Otitis Externa
•
•
•
1.
When it involved the outer ear and ear canal
2.
Also called swimmers ear
Otitis Media
1.
Involves the middle ear
2.
Also called ear infection
Acute Ear Infection
1.
Often painful
2.
Starts suddenly / short period of time
Chronic Ear Infection
1.
Ear infection does not go away / keeps reoccurring
2.
Can cause long term ear damage
OTITIS MEDIA VS
NORMAL MIDDLE EAR
Works Cited
Centers for Disease Control and Prevention. Centers for Disease Control and
Prevention, 30 Sept. 2013. Web. 31 Mar. 2014.
"Ears and Hearing." InnerBody. N.p., n.d. Web. 31 Mar. 2014.
The Editors of Encyclopædia Britannica. "Vestibule (ear)." Encyclopedia Britannica
Online. Encyclopedia Britannica, n.d. Web. 31 Mar. 2014.
"Ménière's Disease." [NIDCD Health Information]. N.p., n.d. Web. 29 Mar. 2014.
"Neuroscience for Kids - The Ear." Neuroscience for Kids - The Ear. N.p., n.d. Web.
31 Mar. 2014.
"Special Senses II: The Ear." Special Senses II: The Ear. N.p., n.d. Web. 31 Mar.
2014.
"X. The Organs of the Senses and the Common Integument. 1d. 4. The Internal
Ear or Labyrinth. Gray, Henry. 1918. Anatomy of the Human Body." X. The
Organs of the Senses and the Common Integument. 1d. 4. The Internal Ear or Labyrinth.
Gray, Henry. 1918. Anatomy of the Human Body. N.p., n.d. Web. 31 Mar. 2014.