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Integumentary System
Turn to your neighbor…what is
the integumentary system?
Skin
Glands
Hair
Nails
FUNCTION: Act as a protective barrier to
the outside world.
Body Bucket
retains body fluids
protects against disease
eliminates waste products
regulates body temperature

Basically, holds all your “stuff” from falling
out or getting contaminated.
How skin protects…
Serving as a barrier against infection and
injury
Helping to regulate body temperature
Removing waste products from the body
Providing protection against ultraviolet
radiation from the sun
Producing vitamin D
Three main layers
Epidermis
Dermis
Hypodermis
Sensory receptors
Perceives sensations such as:
Pressure
Heat
Cold
Pain
All of which are then transmitted to the
nervous system.
EPIDERMIS
Outer most layer of skin
Composed of many sheets of flattened, scaly
epithelial cells
Thin layer of skin made mostly of dead cells
Undergoes rapid cell division
New cells are produced pushing older cells
to the surface of the skin
The older skin begins making keratin
There are no blood vessels in the epidermis
which is why a small scratch will not cause
bleeding
Keratin
Is a tough fibrous protein
Forms basic structure for hair, nails and
calluses
Eventually, the keratin-producing cells die
and form a tough, flexible waterproof
covering on the surface of the skin
Melanin (a dark brown pigment)
Skin pigment
Both light skinned and dark skinned
people have roughly the same number of
melanocytes (cells that produce pigment)
The difference in our skin color is caused
by the amount of melanin the melanocytes
produce and distribute.
Amount of Melanin
Dependent on two factors
Heredity
Length of time skin is exposed to
ultraviolet radiation
Role – absorption of ultraviolet
radiation
DERMIS
Middle thick layer of the skin
composed of living cells
Contains: blood vessels, nerve
endings, glands, sense organs,
smooth muscles, and hair follicles
Helps control body temperature
Body temperature
On cold days, the blood vessels
(arteries) narrow/constrict
• Decreases surface area in order to
conserve body heat
On hot days the blood vessels
(arteries) widen/expand
• warming the skin and increasing heat
loss
Goose Bumps
Tiny muscle fibers attach to hair
follicles contract and pull hair
upright when you are cold or afraid
producing what we call “goose
bumps”
Dermis contains two major glands
Sweat glands
Secretions are stimulated by nerve impulses that
cause the production of sweat when the
temperature of the body is raised
They help cool the body off
Oil glands
Produce oily secretion known as sebum that
spreads out along the surface of the skin and
keeps the keratin rich epidermis flexible and
waterproof
Hypodermis
This layer is beneath the dermis
A layer of fat and loose connective tissue
that insulates the body and acts as an
energy reserve.
What causes blisters and calluses?
the rubbing of the separate skin
layers
the epidermis and the dermis
separate
tissue fluid may collect between the
layers
skin prone to this pressure will create
an area of thicker epidermis causing
a callus
Burns
Severity ranges from minor to fatal
First degree burns
Only the superficial epidermis is affected
Painful but no blistering
Causes death of epidermal cells
Second degree burns
Deeper layers of the epidermis are charred
Inflammations, blisters and painful
…burns continued
Third degree burns
The entire epidermis is charred or burned away,
and the burn may extend into the dermis
Not usually painful at first if the receptors in the
dermis have been destroyed
Extensive third degree burns
Loss of skin
Potentially life threatening because the natural
barrier has been destroyed exposing tissue that
is extremely susceptible to infection and
dehydration
Hair
Produced by cells at the base of the
structures called hair follicles
Hair follicles – tube like pockets of
epidermal cells that extend into the dermis
Individual hairs are actually large columns
of dead cells that have been filled with
keratin
Hair gets color from melanin
Protects and insulates the body
Nails
 Grow from rapidly divided cells known as the nail
matrix or nail root
 Nail matrix is located near the tips of the fingers and
toes
 During cell division, the cells fill with keratin and
produce a tough, strong platelike nail that covers
and protects the tips of the fingers and toes
 The pinkish color comes from the blood vessels in
the nail bed
 Nails grow at a rate of 0.5 to 1.2 mm per day
Finger nails grow faster than toe nails
Diagram of the skin
Fun Facts
Human body’s largest organ
Integumentary derived from a Latin word
meaning “to cover”
The outer layer of dead skin cells is shed
or washed away once every 14 to 28 days