Transcript Skin, Hair, Nails - Sleeping Dog Studios

Skin,
Hair, &
Nails
Skin:
•The
skin, which makes up about
15% of your total body weight,
is the largest organ of the
body.
•Many
specialized structures
are found in the skin, which
along with the hair and nails,
forms the integumentary
system.
Skin:
•The
skin protects the body
from injury, provides the first
line of defense against, helps
regulate body temperature, and
prevents the body from drying
out through evaporation.
•The
skin is made mostly of
connective tissue and layers of
epithelial tissue.
•The
two primary layers of skin
are epidermis and the dermis.
•Epidermis
•The
epidermis is the outermost
layer of the skin.
•About
as this thick as a sheet of
paper, the epidermis is made of
several layers of epithelial cells.
•The
part of the epidermis you
see when you look in a mirror is a
thin layer of flattened, dead
cells that contain keratin.
Epidermis
•Keratin
is a protein that makes skin
tough and waterproof.
•The
cells of the epidermis are
continuously damaged by the
environment.
•They
are scraped, ripped, worn away
by friction, and dried out because of
moisture loss.
•Your
body deals with this damage
not by repairing cells, but by
replacing them.
•The
outermost cells of the skin
are continuously shed and replaced
by a layer of actively dividing cells
at the base of the epidermis.
•As
new skin cells form, they
migrate upward and produce large
amounts of keratin.
•These
cells are shed about a
month after they reach the
surface.
•The
inner layer of the epidermis
also contains cells that produce
the pigment melanin.
•Melanin
ranges in color from
yellow to reddish brown to black,
and it helps to determine skin
color.
•People
with more melanin tend to
have darker skin, and people with
less melanin usually have lighter
skin.
•Melanin
also absorbs UV
(ultraviolet) radiation protecting
the skin from exposure to
sunlight.
•Exposure
to UV radiation
increases the production of
melanin.
•This
is why some people become
“tan” after exposure to UV
radiation.
•However,
UV radiation has also
been shown to cause skin cancer,
especially in people with light skin.
•Thus
you should avoid excessive
exposure to sunlight and wear
sunscreen when outdoors.
Dermis
•The dermis is the functional
layer of the skin that lies just
beneath the epidermis.
•Connective tissue in the
dermis makes the skin tough
and elastic.
•The dermis contains many
nerve cells, blood vessels, hair
follicles, and specialized skin
cells.
Dermis:
Sensations of touch,
temperature, and pain originate
in nerve cells.
The dermis also contains many
tiny muscles that are attached to
hair follicles in your skin.
When you get cold, these
muscles contract and pull the
hair shafts upright, helping to
insulate the body.
These muscles also cause goose
bumps on the skin surface.
Temperature regulation
•A
network of blood vessels in the
dermis provides nourishment to the
living cells of the skin.
•These
blood vessels also help
regulate by temperature by either
radiating heat into the air or
conserving heat.
Temperature regulation
•If
your body gets too hot, blood vessels
just under the skin dilate so that blood
flows near the surface, releasing heat
from the body.
•This
is why people with light
complexions turn red during strenuous
exercise.
•If
your body gets too cold, the blood
vessels constrict, keeping blood away
from the surface and reducing heat loss.
•Sweat
glands in the dermis also help
remove excess body heat.
•The
evaporation of sweat from the skin’s
surface removes heat more efficiently
than the dilation of blood vessels.
•Most
sweat is about 99% water and 1%
dissolved salts and acids.
•Certain
sweat glands located in body areas
with dense hairs, such as the armpits, also
secrete proteins and fatty acids.
•Because
these substances provide a rich
food source for bacteria, stale sweat
often releases the offensive odor of
bacterial waste products.
•Subcutaneous
tissue, located beneath
the skin just under the dermis, is a layer
of connective tissue made mostly of fat.
•Subcutaneous
tissue acts as a shock
absorber, provides additional insulation
to help conserve body heat, and stores
energy.
•Subcutaneous
tissue also anchors the
skin to underlying organs.
•The
thickness of subcutaneous tissue
varies in different parts of the body. For
example, the eyelids have very little while
the buttocks and thighs have a lot.
•The
pads of subcutaneous tissue in the
soles of the feet may be more than 6mm
thick.
Hair and Nails:
•Hair and nails are derived from the
epidermis.
•Hair follicles produce individual
hairs, which help protect and
insulate the body. Hair is made
mostly of dead, keratin-filled cells.
•A shaft of hair grows up from the
hair follicle and up from the skin’s
surface.
•Each hair on your head grows for
several years. Than the follicle
enters a resting phase for several
months and the hair is eventually
shed.
Hair and Nails:
•Hair color is primarily
determined by the presence
of the pigment melanin.
•Blonde hair and red hair
typically contain less melanin
than brown hair or black hair.
•Remember that hair color is a
polygenic trait, one controlled
by multiple genes.
Nails:
•Nails are produced by specialized
epidermal cells located in the
light, semicircular area at the
base of each nail.
•These cells become filled with
keratin as they are pushed
outwards by new cells.
•Nails protect the tips of the
fingers and toes and continue to
grow throughout life.
•The
skin is continuously exposed to
damaging factors such as insect bites,
microorganisms, and ultraviolet radiation.
•Injuries
such as scrapes and blisters
are often minor and usually heal rapidly
without permanent scarring.
•Burns,
however, can be very serious and
can result in permanent scarring.
•Some
skin disorders are a result of
changes that occur within the body over
time.
Acne:
•The most common skin problem
for teenagers is acne, a chronic
inflammatory condition that
involves the skin’s oil-producing
glands.
•Oil glands in the dermis release
sebum, an oily secretion that
lubricates the skin.
•Sebum is released through
ducts, or pores, into nearby hair
follicles.
•These oily glands are especially
active during adolescents.
Acne:
Acne is caused by excessive
secretion of sebum, which blocks
pores with oil, dirt, and bacteria.
Makeup and other cosmetic tissues
can contribute to clogging.
As a result, the surrounding tissue
becomes infected and inflamed, and
the pores accumulate pus, producing
pimples.
Serious acne may need to be treated
using antibiotics. Although acne can
not be prevented, it can be managed
with proper skin care.
Skin Cancer:
•Skin
cancer can result from genetic
mutations caused by overexposure
to UV radiation.
•The
most common types of skin
cancer are carcinomas, which
originate in skin cells that do not
produce pigments.
•If
they are detected early
carcinomas can be treated.
Skin Cancer:
•A small percentage of skin cancers are
caused by mutations that occur in
pigment-producing cells.
•These cancers, called malignant
melanomas, grow very quickly and
spread easily to other parts of the
body.
•About 8 out of 10 skin cancer deaths
are from malignant melanomas.
•You can reduce the risk of skin cancer
by avoiding over exposure to either
natural or artificial UV radiation and by
using protective sunscreens.