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The Special Senses
• Special Senses: Organs and sensory receptors
associated with touch, vision, hearing, taste,
and smell
• Organs include – eyes, ears, nose, tongue, and
sensory receptors of the skin
The Eye
• 10 Facts about the Eye Video
• One inch in diameter sphere
• Protected by:
– Orbital socket /Skull
– Eye lashes and brows
– Lacrimal glands – produce tears which
moisten and cleanse the eye
– Conjunctiva- mucous membrane which
lines eyes and covers front of eye to provide
protection and lubrication
3 layers of eye
1. Sclera
2. Choroid coat
3. Retina
Anatomy of the Eye
3 Layers
Sclera: white of the
• Maintains the shape
of the eye
• Extrinsic muscles responsible for
moving the eye
within socket, are
attached to outside
of sclera
3 layers of eye (cont’d)
2. Choroid layer
– Middle layer of eye
– Vascular
3 layers of the eye (cont’d)
3. Retina – innermost
layer of the eye
Many layers of nerve cells
which transmit light impulses
to optic nerve
2 types of special cells: rods
and cones
Cones – sensitive to bright
light and color - responsible
for color vision
Rods – sensitive to dim light
Ophthalmoscope: used to examine
Fovea Centralis
• Retina viewed through
ophthalmoscope, dark
disc is macula . Within
macula is fovea centralis
which contains cones for
color vision.
• Blind spot (optic disc) –
contains no rods or cones
therefore no visual
Optic Nerve
• 4. Optic Nerve - Cranial Nerve II = responsible
for vision
Vitreous Humor
• 5. Vitreous humor – transparent, jellylike
substance filling posterior chamber of eye
• Helps maintain eyeball’s spherical shape
• 6. Lens- located behind
• Sits in between anterior
and posterior chamber of
• Function is to refract or
bend light as it passes
through – to focus images
on the retina
• Lens held in place by
suspensory ligaments
• 7. Iris – colored muscular layer. Behind cornea
and in front of choroid coat. Contains 2
muscles which control size of pupil and
regulates amount of light entering eye
– 8. Intrinsic muscles – sphincter papillae
– And suspensory ligaments and ciliary body (lens)
• 9. Pupil – opening in center of iris. Light
passes into eye through pupil
Aqueous Humor
• 10. Aqueous humor – water fluid in anterior
chamber of eye
• 11. Cornea – clear,
circular area on front
center of sclerotic coat
• Has pain and touch
receptors making it
sensitive to foreign
particles that come in
contact with its surface
• 12. suspensory
ligaments – holds lens
in place
• 13. ciliary bodies –
smooth muscle
controlling shape of
• 14. Conjunctiva – thin membrane lining the
eyelids and covers part of the eye (anterior
• Secretes mucous to lubricate eye
• Cow Eye Dissection
• Exploratorium Cow Eye Dissection
• Identify and describe your table partner’s:
pupil – how does the pupil react to light/dark
upper lid
lower lid
lacrimal duct (lacrimal canaliculus)
Review of Structures of Eye
• Structures of Eye Video
Application: BS&F pg 180-181
Define the following vision disorders:
Vision Disorders
• Presbyopia – lens loses elasticity resulting in decreased
ability to focus on close objects – usually onset at 40 yo
• Hyperopia – farsightedness – eyeball shorter than
normal – prescription lenses
• Myopia – nearsightedness – eyeball elongatedprescription lenses
• Amblyopia – dimness of vision in one eye, lazy eye. Tx:
covering good eye to strengthen weak eye. If not tx by
8 or 9 yo blindness may occur
• Astigmatism – irregular curvature of cornea or lens
resulting in blurred vision or eye strain – prescription
Vision Disorders (cont’d)
• Strabismus – cross eyes – extrinsic muscles of
eye don’t coordinate activity. Can be corrected
by eye exercises or surgery.
Color blindness
Cone cells of retina
More prevalent in males than females
Red-green – inability to distinguish between
the two colors most common
Vision Simulations
Vision Disorders
• Night blindness – difficult to see at night due
to defect in rod cells
• Color blindness – inability to distinguish colors
– usually heredity
Vision Testing
• Snellen Chart
• Kindergarten eye chart
Vision Testing
• Illiterate Eye Chart
Vision Testing
• Near Vision Chart
Vision Testing
• Ophthalmascope
Eye Injuries
• Chemical or solutions – rinse eye with eye
wash or water
• Fragments or particles – do not attempt to
remove or rub eye, report to supervisor and
seek medical attention
Define the following disorders and S&S and Tx:
Macular degeneration
Detached retina
Eye Disorders
Lens becomes cloudy
Usually as a result of aging
Sometimes by trauma
Leading cause of blindness
in world
Sx: blurred vision, gradual
vision loss, yellowing of
colors, halos around lights
Tx: lens implant
Cataract Surgery
• cataract surgery video
• Pink eye
• Highly contagious
• Viral or bacterial or
• Redness, pain, itching,
• Tx.: antibiotics
Increased intraocular pressure
Excess aqueous humor
Common after 40
2nd leading cause of blindness
Sx – loss of peripheral vision, halos around
lights, limited night vision
• Tx. – medication, surgery
Macular Degeneration
Major cause of blindness
Effects 10% of elderly
Disease of macula – part of retina
Caused by damage to blood vessels which
nourish retina
• S&S: blurred, distorted vision
• Tx: currently no cure
Detached Retina
• Result of aging or traumatic injury
• Tear in the retina
• Loss of peripheral vision followed by loss of
central vision
• Tx: early detection important. Laser surgery
• Hordeolum
• Tiny abscess at base of
• Caused by inflammation
of a sebaceous gland of
• S&S: red, painful,
• Tx: warm, wet
Diabetic Retinopathy
• Damage to retina due to long term diabetes
• Swelling and leaking of vessels that supply
blood to retina
• S&S: pt sees red spots
• Tx: Early detection – laser surgery
Vitreous Floaters
• Small, irregular shaped specks in vision field
• Caused by tiny chunks of gel-like vitreous
humor breaking off and floating in aqueous
• Distracting, not a cause for alarm
• Sudden, multiple floaters with flashes of light
can be sign of retinal detachment
Pathway of light through the eye
• The images in the light “hit” the cornea -> pupil >lens
• The light rays are bent or refracted ->retina >rods and cones pick up the stimulus -> optic
nerve -> optic chiasm (where the two optic
nerves cross) -> optic tracts -> occipital lobe of
the brain for interpretation
(Cornea – pupil-lens-retina-optic nerve-occipital
The Ear
• Special sense organ designed to pick up sound
waves and send the impulses to the auditory
center of the brain
3 anatomical regions of ear:
• External ear – outer - hearing
• Middle ear – tympanic membrane (eardrum) hearing
• Internal ear – inner – hearing and balance
The Outer Ear
• Pinna- collects sound waves and directs them
into the auditory canal to the eardrum or
tympanic membrane, which separates the
outer and middle ear
• The auditory canal is lined with sebaceous or
ceruminous glands that secrete a waxlike
substance called cerumen – cleans, protects
the ear, and lubricates
Outer Ear
• Pinna or auricle –
• Collects sound waves
and directs them to the
auditory canal
• external auditory
meatus or auditory
• Pinna- collects sound waves and directs them
into the auditory canal
• From auditory canal to the tympanic
membrane (eardrum), which separates the
outer and middle ear
• The auditory canal is lined with sebaceous
glands that secrete a waxlike substance called
cerumen – protects the ear (ear wax)
Sound waves enter auricle -> external
auditory canal -> vibrate on tympanic
The Middle Ear
• The middle ear- cavity in the temporal bone
• It connects with the pharynx (throat) by means of
a tube called the Eustachian tube
• The tube equalizes the ear pressure in the
middle ear on both sides of tympanic membrane
– A chain of 3 tiny bones called Ossicles is found in the
middle ear
• Malleus (Hammer)
• Incus (Anvil)
• Stapes (Stirrup)
Malleus, Incus, Stapes – transmit and
amplify sound waves
What happens when we yawn:
• A way to help bring pressure in the pharynx,
Eustachian tube, and middle ear to same level
as pressure outside the ear
• Involuntary – yawn before we’re born
• How Stuff Works: Yawning
• Psychological? Physiological?
Inner Ear
• Most complex portion of ear
• Separated from middle ear by membrane
called oval window
• Vestibule – first section – acts as entrance to 2
other parts of inner ear.
• Cochlea – snail shell shaped – contains,
delicate, hairlike cells, which make up Organ
of Corti
• Organ of Corti – receptor of sound waves –
transmits impulses from sound waves to the
auditory nerve
temporal lobe
interpreted as hearing
• Semicircular canals – located in inner ear –
contain liquid and delicate, hairlike cells that
bend when liquid moves with head and body
movements, maintains our sense of balance
and equilibrium
Pathway of Hearing
• Sound waves -> pinna (auricle) -> auditory
canal -> tympanic membrane -> ossicles ->
stimulate the receptors on the cochlea ->
cochlear nerve (part of vestibulocochlear
nerve) -> temporal lobe of the brain for
Ear disorders
• Otitis media – middle ear
– Infants/children
Eustachian tube not developed
– Bacteria or virus
– Pain, pus, swelling, fever
External Otitis
Swimmer’s ear
Bacterial or fungal
Caused by immersion in contaminated water
S&S: pain, fever, temporary hearing loss
Prevention: throughly cleaning and drying ear
canal with alcohol based solution after
Ear disorders
• Ostosclerosis
– a chronic, progressive disease in which the stirrup
becomes spongy and then hardens
– results in hearing loss
Ear disorders
• Meniere’s disease
– Affects the semicircular canals of the inner ear
– Causes vertigo (dizziness)
– May cause N/V and tinnitus (ringing or buzzing in
the ear)
– Treatments include medications for s/s
• Ringing in ear
• Hair cells in Organ of Corti that stimulate the
auditory nerve are damaged
• Normally, movement of hair cells triggered by
sound waves
• If damaged, hair cells move randomly, generating
ringing in the ear
• Most common cause: exposure to loud noise
(including music)
• Common and growing disorder: 50 million
Inner Ear Infection
Labyrinthitis – infection of inner ear
Inflammation & swelling of inner ear
Semicircular canals
Vertigo (dizziness) and N&V
Ear disorders
• Presbycusis- deafness due to aging
• Hearing loss can result from exposure to loud
noise, conductive loss, and sensorineural
• Hearing aids
• Differentiate between swimmer’s ear, middle
ear infection, inner ear infection.
• Swimmer’s ear – external otitis media –
bacterial or fungal – pain, fever, temp hearing
• Otitis Media –middle ear infection – bacterial
or viral – pain, swelling, pus – common in
children bc Eustachian tube not fully
• Using your smartphone, work with your table
partner to research the following:
• Research products OR services available for
deafness or otitis media.
• What products and/or services are available?
• Discuss findings with your table partner
• Be prepared to share your findings with class
What is a cochlear implant?
Tongue (Taste)
• A mass muscle of tissue which has structures
called papillae
• There are taste buds for sweet, sour, salty, and
bitter that are stimulated by the flavors of
Tongue/Taste facts
• Facial, glossopharyngeal, and vagus nerves
transmit taste sensations to brain
• Flavor is a combination of taste, smell, texture
or consistency, and temperature
• 75%-90% of what we taste is actually due to
what we smell
• Parietal lobe – taste/smell sensations
Lab: What is difference bw taste and
Hold your nose, chew jelly bean. What flavor is
jelly bean? Describe what you taste.
Let go of your nose. Continue chewing jelly
bean. What happens? Did you get a sudden
rush of flavor? Can you better identify flavor of
jelly bean?
What did you learn from this simple
Tongue disorders
• Hairiness- over growth of the normal
• Discoloration- tongue may appear black if the
person takes bismuth preparations for an
upset stomach
• Infection- may be the result of tongue
• Cancer- sores, lumps, discoloration, etc
Hairy tongue, smoker’s tongue,
cancer of tongue
The Nose (Smell)
• Detects about 10,000 smells
• The specialized patch of tissue called the
olfactory epithelium has the receptors that
send stimuli to the olfactory nerve
• Smell accounts for about 90% of what we
think of taste
• Inflammation of mucous membranes that line
nasal passages
• Most common cause – common cold
• Allergies, chemical odors, illegal drugs
Why do I get a runny nose?
• Inflammation of nasal membranes causes
release of histamines
• Histamines – molecules which trigger a
reaction that produces congestion and
• Tx: removing or minimizing irritant,
antihistamines (decrease production of
Nose disorders
• Rhinitis- inflammation of the lining of the nose
• Nasal polyps- growths in the naval cavity
• Deviated nasal septum- a bend in the cartilage
structure of the septum
• The sense of touch is due to very sensitive
neurons that respond to pressure, heat, cold,
touch, and pain
• Each receptor perceives only one type of
Careers related to Special Senses