THE INTEGUMENTARY
SYSTEM
Chapter 24A
HUMAN SKIN
Skin Stats …
Approx 1.9 square meters (about 18
sq. feet) of skin cover the body
Average thickness is 1/8 inch (1-2
mm)
Weighs 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
Sensation
Heat Control
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.
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
mircroorganisms.
SENSATION
(Communication)
Nerve receptors for touch,
pressure, temperature, and pain
are in the skin. Communication
between your body and the
outside world.
HEAT CONTROL
The amount of blood being carried
to the surface of the skin is
regulated to control the amount of
heat lost to the atmosphere. 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.
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
Epidermis (1)
Dermis (2)
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
Dermis
the inner, much thicker layer of the skin
contains: connective tissues
blood vessels
nerve endings
sweat glands
hair follicles
oil glands
Nerve Receptors
Cold
Heat
Touch
pressure
Subcutaneous layer
not actually a part of the skin
consists of loosely arranged fat cells and
fibers
the fat cells help to cushion and insulate
you body
the fibers attach the skin to the muscles
under it
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.
Albinism
People with albinism do not have the
ability to make melanin and thus cannot
tan.
Callus
a thickened
epidermis
which helps
protect the
deeper layers
of the skin
Blisters
Blisters are not a form of protection, but a
response to injury.
Friction causes
layers of skin to
separate and
water collects in
the space between
the separated layers.
Boils
Boils are bacterial infections (the raised
portion of skin is filled with pus)
Burns
Burns are classified by how deeply they
penetrate the skin’s surface.
First Degree
Second Degree
Third Degree
First Degree
(superfiecial)
involves only the epidermis
Second Degree
(partial thickness)
involves the epidermis and some of the
dermis
Third Degree
(full thickness)
destroys the epidermis, dermis, and into the
subcutaneous tissues
Burns
Burns are classified by how deeply they
penetrate the skin’s surface.