Transcript How Are Ear Tubes Inserted?

Chapter 8
Special Senses
The Ear
 Houses two senses
 Hearing
 Equilibrium (balance)
 Receptors
 Sound receptors
 Mechanoreceptors
 Both stimulated by the movement of fluid
Anatomy of the Ear
 The ear is divided into three major
areas
 Outer (external) ear
 Middle ear
 Inner (internal) ear
Outer (external) Ear
 Involved in
hearing only
 Structures of
the external
ear
 Pinna
(auricle)
 External
auditory canal
The External Auditory Canal
 Short, narrow chamber in the temporal
bone of the skull
 Lined with skin
 Ceruminous (wax) glands are present
that secrete earwax or cerumen
 Sound waves entering the canal
eventually hit the tympanic membrane
or eardrum and cause it to vibrate
 Canal ends at the eardrum, which
separates the outer from the middle ear
The Middle Ear or Tympanic Cavity
 Air-filled cavity within the temporal bone
 Only involved in the sense of hearing
 Pharyngotympanic (auditory) tube
 Runs obliquely downward to link the
middle ear cavity with the throat
 Allows for equalizing pressure during
yawning or swallowing
 Tube is otherwise collapsed
Bones of the Tympanic Cavity
 3 of the smallest
bones in the body
span the cavity
(ossicles)
 Malleus (hammer)
 Incus (anvil)
 Stapes (stirrup)
Bones of the Tympanic Cavity
 Vibrations from
the eardrum
moves the
malleus
 These 3 bones
transfer sound
to the inner ear
Inner Ear or Bony Labyrinth
 A maze of bony chambers within the
temporal bone
 Cochlea
 Vestibule
 Semicircular
canals
Inner Ear or Bony Labyrinth
 Includes sense organs for hearing &
balance
 Filled with perilymph
Mechanism of Equilibrium
 Equilibrium has two functional parts
 Static equilibrium
 Receptors in the vestibule
 Dynamic equilibrium
 Receptors in the semicircular canals
Static Equilibrium
 Maculae – receptors within the vestibule
 Report on the position of the head with
respect to the pull of gravity when the body
is not moving (static = rest)
 Anatomy of the maculae
 Hair cells are embedded in the otolithic
membrane
 Otoliths (tiny stones) float in a gel around
the hair cells
 Movements cause otoliths to bend the hair
cells  sends impulses along the vestibular
nerve to the cerebellum of the brain
Function of Maculae
Dynamic Equilibrium
 Responds to angular or rotatory movements
of the head
 Crista ampullaris – receptors found within the
semicircular canals
 Tuft of hair cells are covered with a
gelatinous cap called the cupula
Dynamic Equilibrium
 During angular head
movements
 The cupula stimulates the
hair cells
 An impulse is sent via the
vestibular nerve to the
cerebellum
Mechanism of Hearing
 Organ of Corti
 Located within the cochlea
 Hearing receptors  hair cells on the
basilar membrane
 Gel-like tectorial membrane is capable of
bending hair cells
 Cochlear nerve attached to hair cells
transmits nerve impulses to auditory cortex
on temporal lobe
Hearing- Anatomy of the Cochlea
Mechanisms of Hearing
 Vibrations from sound waves move
tectorial membrane
 Hair cells are bent by the membrane
 An action potential starts in the
cochlear nerve
 Continued stimulation can lead to
adaptation
Chemical Senses: Taste & Smell
 Both senses use chemoreceptors
 Stimulated by chemicals in solution
 5 types of taste receptors
 Smell (olfactory) receptors
 Sensitive to a much wider range of
chemicals
 Receptors for both senses complement
each other and respond to many of the
same stimuli
Olfaction – The Sense of Smell
 Olfactory receptors are in the roof of
each nasal cavity
 Neurons with long cilia (olfactory hairs)
 Chemicals must be dissolved in mucus for
detection
 Impulses are transmitted via the
olfactory nerve
 Interpretation of smells is made in the
olfactory cortex of the brain
Olfactory Epithelium
The Sense of Taste
 Taste receptors 
Taste buds (Widely
scattered throughout
the oral cavity)
 Location of taste
buds
 Most are on the
tongue
 Soft palate
 Inner surface of
the cheeks
The Tongue and Taste
 The tongue is covered with 3 types of
projections called papillae
 Sharp or Filiform papillae – no taste buds
 Fungifiorm papillae – rounded with taste
buds
 Circumvallate papillae – large papillae
with taste buds
 Taste buds are found on the sides of
papillae
Structure of Taste Buds
 Gustatory cells
 Have gustatory hairs (long microvilli)
 Hairs are stimulated by chemicals
dissolved in saliva and transmit impulses
to the brain
Structure of Taste Buds
 Impulses are carried to the gustatory
complex by several cranial nerves
because taste buds are found in
different areas
 Facial nerve
 Glossopharyngeal nerve
 Vagus nerve
Anatomy of Taste Buds
Taste Sensations
 Sweet receptors
 Sugars
 Saccharine
 Some amino acids
 Sour receptors
 Acids
 Bitter receptors
 Alkaloids
 Salty receptors
 Metal ions
 Umami
 Glutamate- “Beef taste” of steak
 Chipped
or broken teeth
 Infection

And possibly death
Girl who almost died from a brain
abscess following a tongue piercing
 She had part of her skull removed
to relieve pressure caused by the
infection
 She can still feel the soft spot
where the skull is missing
 Rare, but real


Blood loss


There is also the possibility of hitting and
damaging a nerve


The tongue contains large blood vessels, and you're in
trouble if one of them is perforated. You could end up
having to have the vessel closed surgically in hospital.
Imagine life with a tongue that doesn't work properly!
Lingering pain

Cases of neuralgia - severe, long-lasting nerve pain
 Hepatitis

or HIV
Unsterile instruments are a great way to spread
these and other infections
Still not convinced?
If
you must do this, be sure to go
to a reputable clinic, and be very
sure that they do things properly:
autoclave sterilization and gloves.
As we had tried to teach you with
tattooing, be a smart consumer!
Developmental Aspects of the
Special Senses
 Formed early in embryonic development
 Eyes are outgrowths of the brain
 All special senses are functional at birth
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 8.42
Normal
slight
severe ear infection
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How Are Ear Tubes Inserted?
Ear tubes are inserted through an outpatient surgical procedure called a myringotomy. A
myringotomy refers to an incision (a hole) in the ear drum or tympanic membrane. This is
most often done under a surgical microscope with a small scalpel (tiny knife), but it can
also be accomplished with a laser. If an ear tube is not inserted, the hole would heal and
close within a few days. To prevent this, an ear tube is placed in the hole to keep it open
and allow air to reach the middle ear space (ventilation).
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Ear Tube Surgery
A light general anesthetic (laughing gas) is administered for young children. Some older
children and adults may be able to tolerate the procedure without anesthetic. A
myringotomy is performed and the fluid behind the ear drum (in the middle ear space) is
suctioned out. The ear tube is then placed in the hole. Ear drops may be administered
after the ear tube is placed and may be necessary for a few days. The procedure usually
lasts less than 15 minutes and patients awaken quickly. Sometimes the otolaryngologist will
recommend removal of the adenoid tissue (lymph tissue located in the upper airway
behind the nose) when ear tubes are placed. This is often considered when a repeat tube
insertion is necessary. Current research indicates that removing adenoid tissue concurrent
with placement of ear tubes can reduce the risk of recurrent ear infection and the need
for repeat surgery.
 Vertigo-website
 Tinnitus-website
 Adaptation:
decreasing sensitivity
 Threshold: minimal amount of stimulus
needed to illicit a response.
 Taste:

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Adapt: complete 1-5 minutes
Threshold: bitter lowest (poisons), sour, salt &
sweet
 Smell:
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Adapt: 50% after 1 sec.
Threshold: very low 1/25,000,000,000mg/ml.