Integumentary System
The integumentary system, consisting of the skin, hair and
nails, act as a barrier to protect the body from the outside
world. It also functions to retain body fluids, protect against
disease, eliminate waste products, receive sensory input, and
regulate body temperature.
OBJECTIVES:
1. Describe the functions of the skin.
2. Distinguish between the two layers that form the skin.
3. Identify two types of glands found in the skin, and
describe their functions.
4. Describe the structure of nails.
5. Describe the structure of hair.
Skin
1. SKIN AND ITS ACCESSORY ORGANS-THE HAIR, NAILS, AND A
VARIETY OF GLANDS, MAKE UP THE INTEGUMENTARY SYSTEM.
2. The Skin is the human body's largest organs.
3. The word INTEGUMENT comes from a LATIN word that means to
COVER.
4. THE MOST IMPORTANT FUNCTION OF THE INTEGUMENTARY
SYSTEM IS PROTECTION.
5. IT PERFORMS THIS FUNCTION BY: (The SIX Main Functions of the
Integumentary System)

A. SERVING AS A BARRIER AGAINST INFECTION AND
INJURY.

B. HELPING TO REGULATE BODY TEMPERATURE.

C. REMOVING WASTE PRODUCTS FROM THE BODY.

D. PROVIDING PROTECTION AGAINST ULTRAVIOLET
RADIATION FROM THE SUN.

E. PRODUCING VITAMIN D.

F. SENSORY RECEPTION.
6. Because the skin contains several types of
sensory receptors, it serves as the gateway
through which sensations such as PRESSURE,
HEAT, COLD, AND PAIN ARE
TRANSMITTED TO THE NERVOUS
SYSTEM.
7. The skin is composed of two main layers - The
EPIDERMIS and DERMIS.
Epidermis
1. The OUTER most layer of skin is known as the EPIDERMIS. It is
composed of many sheets of flattened, scaly epithelial cells. This is a thin
outer layer of skin.
2. Its layers are made of mostly DEAD CELLS.
3. Most of the cells of the epidermis undergo rapid cell division (MITOSIS).
4. As new cells are produced, they push older cells to the surface of the
skin. The older cells become flattened, lose their cellular contents and
begin making KERATIN.
5. KERATIN IS A TOUGH FIBROUS PROTEIN AND FORMS THE
BASIC STRUCTURE OF HAIR, NAILS, AND CALLUSES.
6. In animals keratin forms cow horns, reptile scales, bird feathers, and porcupine
quills.
7. Eventually, the keratin-producing cells (KERATINOCYTES) DIE AND
FORM A TOUGH, FLEXIBLE WATERPROOF COVERING ON THE
SURFACE OF THE SKIN. Our thickest epidermis in on the palms and
soles.
8. THIS OUTER LAYER OF DEAD CELLS IS SHED OR WASHED AWAY
ONCE EVERY 14 TO 28 DAYS.
9. The Epidermis contains MELANOCYTES, CELLS THAT
PRODUCE MELANIN, A DARK BROWN PIGMENT.
10. BOTH LIGHT SKINNED AND DARK SKINNED
PEOPLE HAVE ROUGHLY THE SAME NUMBER OF
MELANOCYTES, THE DIFFERENCE IN OUR SKIN
COLOR IS CAUSED BY THE AMOUNT OF MELANIN
THE MELANOCYTES PRODUCE AND DISTRIBUTE.
11. The amount of melanin produced in Skin depends on TWO
Factors - Heredity and the Length of Time the Skin is Exposed
to Ultraviolet Radiation (Tanning).
12. Melanin is important for protection, by absorption of
Ultraviolet Radiation from the sun. All people, but especially
people with Light Skin, need to minimize exposure to the sun
and protect themselves from its Ultraviolet Radiation, which can
Damage DNA in Skin Cells and lead to deadly forms of Skin
Cancer such as MELANOMA CANCER.
13. THERE ARE NO BLOOD VESSELS IN THE EPIDERMIS,
WHICH IS WHY A SMALL SCRATCH WILL NOT CAUSE
BLEEDING.
Dermis
1. THE DERMIS IS THE INNERMOST THICK LAYER OF
THE SKIN COMPOSED OF LIVING CELLS. IT LIES
BENEATH (DEEP TO) THE EPIDERMIS.
2. The outer (superficial) region of the Dermis consists of areolar
connective tissue. This region’s surface area is greatly increased
by the formation of DERMAL PAPILLAE, which project up
into the epidermis to supply the epidermis with important
compounds from blood vessels and contain several different
types of sensory receptors. The Dermal Papillae form the
EPIDERMAL RIDGES, which form our fingerprints that help
us to grip objects.
3. The inner (deep) region of the Dermis consists of dense
irregular connective tissue, adipose tissue, BLOOD VESSELS,
NERVE ENDINGS, GLANDS, SENSE ORGANS, SMOOTH
MUSCLES, AND HAIR FOLLICLES.
4. The Dermis helps us to control our body temperature:
A. On a cold day when the body needs to conserve
heat, the Blood Vessels in the Dermis NARROW.
B. On hot days, the Blood Vessels WIDEN, warming
the skin and increasing heat loss.
C. Tiny Muscle fibers called ARRECTOR PILI attach
to Hair Follicles contract and pull hair upright when
you are cold or afraid, producing what is commonly
called Goose Bumps.
5. The Dermis contains TWO major types of GLANDS:
SUDERIFEROUS OR SWEAT GLANDS AND
SEBACEOUS, OR OIL GLANDS.
6. These Glands PASS through the Epidermis and
RELEASE THEIR PRODUCTS AT THE SURFACE
OF THE SKIN.
7. SUDERIFEROUS (SWEAT) GLANDS
PRODUCE THE WATERY SECRETIONS KNOWN
AS PERSPERATION OR SWEAT, WHICH
CONTAINS SALT, WATER, AND OTHER
COMPOUNDS.
8. These secretions are stimulated by nerve impulses that
cause the production of sweat when the temperature of
the body is raised. They help to cool the body.
9. SEBACEOUS GLANDS, (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.
10. The production of Sebum is controlled by Hormones.
11. Oil Glands are usually connected by Tiny Ducts
(Exocrine Glands) to Hair Follicles. Sebum coats the
surface of the skin and the shafts of hair, preventing
excess water loss and lubricating and softening the Skin
and Hair.
12. Sebum is mildly toxic to some Bacteria - protection.
13. If the Ducts of Oil Glands become clogged with
excessive amounts of Sebum, Dead Cells, and Bacteria,
the Skin disorder ACNE can result.
14. Other glands in the dermis include
CERUMINOUS GLANDS and MAMMARY
GLANDS.
CERUMINOUS GLANDS produce and a
waxy secretion known as CERUMEN and are
found in the outer ear canal. Cerumen and hair
form a sticky barrier to foreign invaders.
MAMMARY GLANDS are modified
suderiferous glands that produce milk in nursing
(lactating) mothers. The production and
ejection of milk is controlled by hormones.
Hypodermis
Beneath the Dermis is the HYPODERMIS, OR
SUBCUTANEOUS LAYER (SUB Q), A
LAYER OF ADIPOSE AND AREOLAR
CONNECTIVE TISSUE THAT CONNECTS
THE SKIN TO THE UNDERLYING
MUSCLES AND BONES. IT INSULATES
THE BODY AND ACTS AS AN ENERGY
RESERVE. The Hypodermis also contains the
large blood vessels that supply the skin.
Hair and Nails
1. HAIR IS PRODUCED BY CELLS AT THE BASE OF
STRUCTURES CALLED HAIR FOLLICLES. (Figure 45-15)
2. Hair Follicles are tubelike pockets of Epidermal Cells that extend
into the Dermis.
3. Individual hairs are actually large columns of DEAD Cells that
have filled with KERATIN..
4. Rapid cell growth at the base of the Hair Follicle in the HAIR
ROOT causes hair to grow longer. Hair gets its color from
Melanin.
5. Hair Follicles are in close contact with Sebaceous Glands. The
oily secretions of these Glands help maintain the condition of
each individual hair.
6. Hair protects and insulates the body.
7. Most individual hairs grow for several years and then fall out.
8. NAILS GROW FROM AN AREA OF
RAPIDLY DIVIDING CELLS KNOWN AS
THE NAIL MATRIX or NAIL ROOT.
9. THE NAIL MATRIX IS LOCATED NEAR
THE TIPS OF THE FINGERS AND TOES.
10. 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.
11. Nails rest on a Bed of tissue filled with Blood
Vessels, giving the nails a Pinkish Color.
12. Nails grow at a rate of 0.5 to 1.2 mm per day,
with fingernails growing faster than toenails.