THE INTEGUMENTARY
SYSTEM
C14L3
HUMAN SKIN
Integumentary System
skin
hair
nails
Skin Stats …
Approx. 28 hundred sq. inches
(about 18 sq. feet) of skin cover the
body
Average thickness is 1/8 inch
Weighs 6-9 pounds (6% of the body
weight)
Skin is the largest organ of the
human body
A piece of skin the size of a
quarter contains:
1 yard of blood vessels
4 yards of nerves
25 nerve endings
100 sweat glands
more than 3 million cells
FUNCTIONS OF THE SKIN
Protection
Sensory Response
Temperature Regulator
Excretion
Manufacture
Absorption
Protection
(a mechanical shield)
Your skin is one of your body’s major
defenses. The skin does not permit
significant amounts of substances like water
in or out of the body. It keeps your body
from drying out.
Bacteria, viruses, and many common
chemicals that you constantly touch would
be very harmful if they penetrated into the
body. Skin is an effective barrier to most of
them.
Protection
(a mechanical shield)
Perspiration and oils secreted by the skin
provide a form of chemical protection which
is acidic and sometimes has enzymes that
inhibit the growth of certain
microorganisms.
Sensory Response
Nerve receptors for pressure,
temperature, and pain are in the
skin. Communication between
your body and the outside world.
The more sensory receptors there
are in an area of skin, the more
sensitive it is.
Temperature Regulator
The amount of blood being
carried to the surface of the
skin is regulated to control
the amount of thermal
energy released. Blood vessels in skin
dilate when you need to cool off and
constrict when you need to conserve
heat. Also evaporation of sweat cools
the body.
EXCRETION
(Secretion)
A small amount of body wastes is
excreted with sweat.
sweat glands – move moisture to the
surface to cool, also give off certain
wastes to help keep the body clean
oil glands (sebaceous) – coat the skin
with oils to keep it from drying out.
VITAMIN MANUFACTURE
The skin produces small amounts of
vitamin D if exposed to sunlight.
Vitamin D helps
it absorb calcium
and phosphorous
to promote bone
growth.
As little as 15-20 minutes of
sunlight 2-3 days a week will
produce sufficient vitamin D.
ABSORPTION
The skin can absorb some
chemicals, a few
drugs, and a
small amount
of oxygen.
Layers of the Skin
1
2
3
Epidermis (1)
Dermis (2)
Hypodermis (3)
Epidermis
the outermost layer of the skin has dead cells
at the surface and living cells underneath
contains nerve endings (example: pain
receptors)
the older cells of the epidermis fill with a
waxy substance called keratin and die
approximately every 25 days (faster for some
people and in some areas of the body) a
completely new epidermis covers the body
Epidermis
The epidermis produces melanin, which is a
pigment that protects the body by absorbing
some of the Sun’s damaging ultraviolet rays.
Dermis
the inner, much thicker layer of the skin;
giving skin strength, nourishment, and
flexibility.
contains: connective tissues
blood vessels
nerve endings
sweat glands
hair follicles
oil glands
Hypodermis layer
consists of loosely arranged fat
cells and fibers
the fat cells help to cushion and
insulate you body
and store energy
Skin
Skin Color
Pink color of a person's skin is his blood
showing through.
Other colors are the results of pigments.
dark pigment - melanin
yellowish pigment - carotene
Melanin
Melanin is produced by special cells
(melanocytes) in the skin.
Freckles
Freckles are clumps of cells that contain
more melanin that the rest of the skin.