Sense organs

Special Sense organs

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Sense Organs
Copyright © 2016 by Elsevier Inc. All rights reserved.
By: Iffat Aisha

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Special Sense Organs
Your senses are means of detecting and interpreting stimuli
of you external environment.
These are the sense of taste, sight, hearing, touch and smell.
A sensory organ is a specialised organ that allows for the
reception of a stimulus, the formation of an impulse and it’s
transmission to the brain for interpretation.
The main sense organs are your eyes, ears, olfactory organs in
your nose, taste buds on your tongue and your skin.
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The Skin
Theskinistheouterlayerofvertebrateanimals.Itsmajor
functionsareprotection,temperatureregulationandtoact
asasenseorgan.
Twomajorlayersoftheskin:epidermisanddermis.
Epidermis
Theepidermisistheouterrenewablelayeroftheskin.
MalpighianLayer:Thisisthebaselayer,whichisconstantly
producingnewcellsbymitosis.Thenewcellsarepushed
towardsthesurface.Thedarkpigmentmelaninisproduced
here.
GranularLayer:Theproteinkeratinaccumulatesinthecells
givingthemagranularappearance.Thecellsfinallydie.
CornifiedLayer:Thisisthesurfacelayerofdeadkeratinised
cells,whichisconstantlybeingeroded.

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Functions of the Skin
Protection
Prevents excessive loss of water (the cornified layer of
the epidermis is waterproof).
Prevents the entry of pathogens.
‘Sebum oil’ keeps the skin intact preventing it from
‘cracking’.
Sebum from the sebaceous glands contain anti-
microbial chemicals.
Melanin gives protection against the damaging UV rays
of sunlight.
The dermis and adipose tissue protect against
mechanical injury.

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Functions of the Skin
Energy Storage
There is a layer of fat storage adipose tissue below the
dermis of the skin.
Fat is also a poor conductor of heat and so the skin
acts as a heat insulator.
This fat layer also acts as a shock absorber protecting
against mechanical damage.
The Skin is a Homeostatic Organ!

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•Outer layer of our skin,
•It is the tough, protective
outer layer.
•It is about as thick as a
sheet of paper over most
parts of the body.
•Constantly flaking off
and being renewed

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Middle layer of skin
The dermis contains….
1.Nerve endings-howthings feel
2.Blood vessels-carryblood
3.Oil glands-Produce Sebum
4.Sweat glands-produce sweat

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Bottom layer
1.made mostly of fat
2.helps your body stay warm
3.absorb shocks
4.Each hair on your body grows
out of a tiny tube in the skin
called a follicle
5.Every follicle has its roots way
down in the subcutaneous layer
and continues up through the
dermis.

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The Skin
1. Epidermis
2. Dermis
3. Subcutaneous
5. Sweat Gland
4. Oil Gland
6. Hair
Nerves
7.
Blood Vessels
8.
Fat Cells 9.

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Special Senses: Vision (Cont.)
Conjunctiva
Mucous membrane covering the front surface of the
sclera and also lines the eyelid
Kept moist by tears found in the lacrimal gland
Lens
Transparent body behind the pupil
Focuses light rays on the retina
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Special Sense Organs
Copyright © 2016 by Elsevier Inc. All rights reserved.

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Special Senses: Vision
Structure and function of the eye (Figure 10-2)
Sclera
Tough outer coat; “white” of eye; cornea is transparent part
of sclera over iris
Choroid
Pigmented vascular layer prevents scattering of light; front
part of this layer made of ciliarymuscle and iris, the
colored part of the eye; the pupil is the hole in the center of
the iris; contraction of iris muscle dilates or constricts
pupil
Retina (Figure 10-4)
Innermost layer of the eye; contains rods (receptors for
night vision) and cones (receptors for day vision and color
vision)
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The Eye
Copyright © 2016 by Elsevier Inc. All rights reserved.

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Cells of the Retina
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Special Senses: Vision (Cont.)
Structure and function of the eye
Eye fluids
Aqueous humor: In anterior chamber in front of the lens
Vitreous humor: In posterior chamber behind the lens
Visual pathway
Innermost layer of retina contains rods and cones
Impulse travels from the rods and cones through the bipolar
and ganglionic layers of retina (Figure 10-4)
Nerve impulse leaves the eye through the optic nerve; the
point of exit is free of receptors and is therefore called a blind
spot
Visual interpretation occurs in the visual cortex of the
cerebrum
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The Ear
The ear has two major functions:
Hearing: detection of vibrations, their frequency
(pitch) and amplitude (loudness).
Balance: detection of direction of motion,
acceleration and head position related to gravity.
It is divided into three sections, the outer ear, middle
earand inner ear.

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Special Senses:
Hearing and Equilibrium
The ear functions is hearing, equilibrium and balance.
External ear
Auricle (pinna)
External auditory canal
Curving canal 2.5 cm (1 inch) in length
Contains ceruminous glands
Ends at the tympanic membrane
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The Ear
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Hearing and Equilibrium
Middle ear
Within the middle ear, a mechanical linkage is provided
between the tympanic membrane and the membrane
closing the vestibular window by three auditory ossicles
(bones).
1.Incus–hammer
2.Malleus–anvil
3.Stapes –stirrup
Middle ear separated by inner ear by membranes that close
the vestibular (oval) window and cochlear (round) window
Middle ear communicates with the pharynx by way of the
auditory tube (Eustachian tube)
Auditory tube allows for pressure equalization
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Special Senses:
Hearing and Equilibrium
Inner ear
Can be divided into two parts according to function
1.Vestibular portion which is sensory for position and balance
and receivesbranch of cranial nerve VIII (vestibulocochlear)
2.Cochlear portion which is sensory for sound and receives the
cochlear nerve, a branch of cranial nerve VIII
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Inner Ear
Bony labyrinth filled with perilymph.
Subdivided into the vestibule, semicircular canals, and cochlea.
Membranous labyrinth filled with endolymph
Copyright © 2016 by Elsevier Inc. All rights reserved.

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The Inner Ear
Copyright © 2016 by Elsevier Inc. All rights reserved.
The receptors for balance in the semicircular canals are called cristae
ampullares.
Specialized hair cells on the organ of Corti respond when bent by the
movement of surrounding endolymph set in motion by sound waves.

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Effect of Sound Waves in the Ear
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Special Senses: Taste
Receptors are chemoreceptor's called taste buds.
Two cranial nerves (VII and IX) carry gustatory
impulses.
Most pathologists list four kinds of “primary” taste
sensations: Sweet, sour, bitter, and salty.
Metallic and umami (meaty) tastes are also unique
and may soon be added to the list of “primary” taste
sensations
Nasal congestion interferes with stimulation
of olfactory receptors and thereby dulls taste
sensations
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Special Senses: Taste ( Tongue)
-Humans have four kinds of
taste buds.
-They can detect four kinds of
tastes:
sweet, sour, salty and bitter.

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Special Senses: Taste ( Tongue)
Gustatory and olfactory senses work together
to permit creation of many other taste sensations
Copyright © 2016 by Elsevier Inc. All rights reserved.

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Eat
Speech
Taste
The tongue moves and
pushes a small bit of
food along with saliva
into your esophagus,
which is a food pipe
that leads from your
throat to your
stomach.
•The top of your tongue is covered with a layer of bumps
called papillae
•. Papillae help grip food and move it around while you chew.
•They contain your taste buds, so you can taste everything.

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The Sense of Taste
There are four primary taste qualities: bitter, sour,
salty, sweet.
Most tastes are combinations of these.
The taste receptors are collected in groups of about ten
in the taste buds.
Taste buds are present on the tongue’s edges and upper
surface.
Taste buds are also present on the soft palate and on
the back of the pharynx.
Certain regions of the tongue are more sensate to a
particular primary tastes than others.

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The Sense of Smell
The olfactory region is high up in the nasal cavity
about 5 cm
2
in area with about 20,000 receptors.
Stimulatory chemicals must be volatile and soluble in
water.
There are 50 primary smell qualities but in
combination they can produce over 3,000 different
odours.
Prolonged exposure to a particular chemical causes
fatigue of that sensation.

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Special Senses: Smell
Receptors for fibers of olfactory or cranial nerves lie in
olfactory mucosa of nasal cavity
Olfactory receptors are extremely sensitive but easily adapt
(become fatigued)
Odor-causing chemicals initiate a nervous signal that is
interpreted as a specific odor by the brain
Copyright © 2016 by Elsevier Inc. All rights reserved.

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Integration of Senses
Sensations are all perceived in the brain, not at individual
receptors scattered throughout body.
Severe nasal congestion can interfere with the stimulation of
olfactory receptors by food odors in the mouth, which leads
to dull flavor sensations.
Smell sensations are often powerful triggers of memory.
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Structures of the ear
The OUTER EAR
________________: (pinna) Collects sound waves
________________: sound waves pass through to the
ear drum.
Ear Lobe
Ear Canal

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Structures of the ear
Ear Drum
Ossicles
The MIDDLE EAR
________________: thin membrane that vibrates( stretched across the
ear canal)
________________: three small bones which help carry the sound
waves (hammer, anvil, and stirrup)

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Structures of the ear
Cochlea
Semicircular
Canal
The Inner EAR
________________: coiled tube in the inner ear (snail shaped) filled with liquid and
hair like cells.
________________: three small tubes in the inner ear which control your balance
________________: carries impulses from the ear to the brain
Auditory Nerve

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How does it all work?
1.____________________ are collected in the outer ear.
2.Sound waves pass through our _________________ and cause our
ear drum to vibrate.
3.These _________________________ are sent to our inner ear by
the ossicles. (small bones in the middle ear)
4.The vibrations reach the ______________________. The fluid in
the cochlea begins to move, this motion results in the hair cells
sending a signal along the auditory nerve to the brain.
5.Our __________________ receives these impulses and interprets
them as a type of sound.
Sound Waves
Ear Canal
Vibrations
Brain
Cochlea

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Ear Problems
1.____________________ in the middle ear are the most
common ear problems. Germs from colds in the nose or
throat can spread through the Eustachian tube in the
middle and inner ear.
2.Hearing loss and deafness-This can result from injury,
disease, birth defects, and very loud noises.
•___________________________: is someone who is
specially trained to test and help with the problems
related to hearing loss.
Audiologist
Infections

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Structures of the eye
Cornea
Iris
Cornea
Optic
Nerve
________________: Transparent coating which covers
the iris and the pupil at the front of the eye.
________________: The colored part of the eye that
regulates the amount of light entering the eye.

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Structures of the eye
Pupil
Lens
________________: The opening at the center of the iris.(hole)
________________: A clear part of the eye behind the iris that helps
to focus light, or an image on the retina
Optic Nerve
Cornea

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________________: The light-sensitive tissue lining at the back of the
eye. The retina converts light into electrical impulses that are sent to
the brain through the optic nerve)
________________: A bundle of more than one million nerve fibers
that carries visual messages from the retina to the brain.
Optic Nerve
Structures of the eye
Retina
Optic Nerve
Corne
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How does it all work?
1.____________________ bounce off an object you are looking at.
2.Light then enters through the outer part of the eye, called the
___________________.
3.Next, light rays go through an opening called the _____________.
4.Light passes through the lens on its way to the back of the eye.
5.The retina sees the world upside down, but the ___________ turns
it right side up.
6.When you look at an object, each eye sees a slightly different
picture. The brain combines the images into one picture.
Light Rays
Cornea
Pupil
Brain

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Eye Problems
1.____________________ It can cause redness, itching, inflammation
or swelling, and a clear or white, yellow, or greenish gooey liquid to
collect in the eyes.
2.____________________ someone can see stuff that's near, like a
book, but has trouble seeing stuff that's far away.
3.____________________ someone can see stuff that's far away, but
has trouble seeing up close, like reading the print in a book.
4.____________________ A misshaped cornea or lens causing
objects to look blurry
Pinkeye
Farsighted
Nearsighted
Astigmatism

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Eye Care
1.Visiting an ____________________ (a medical
doctor who specializes in examining, diagnosing,
and treating eyes)at least every 2 years
2.Wearing sunglasses
3.Wearing protective eyewear whenever you play
sports
4.Take breaks from the computer, video games, or
watching TV
1.staring for a long time —can strain your eyes.
5.Never share eye glasses or eye care products
ophthalmologist

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