The Integumentary System
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Skin and derivatives
Sweat Glands
 Oil Glands
 Hair
 Nails
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Amazing Facts About Skin
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The skin is waterproof.
The outer surface is made of dead cells.
House dust is 90% skin flakes!
Skin is the largest organ in the body!
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It weighs 2.5 kg.
Skin is elastic.
If you laid skin on a flat surface, it would have an
area of 2 square meters!
Your hair stands on end and you develop
“goosebumps” when the muscles in the hair
follicles contract b/c you’re cold or scared.
Skin Functions
Integument – means covering
 Functions are mostly protective:
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Mechanical damage – ex. Cuts
 Chemical damage
 Thermal damage – burn
 UV radiation – sunlight
 Bacteria
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Also insulates and cushions internal
organs.
Skin Functions
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Waterproof
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Temp. regulation
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Keeps water in and keeps water out
Capillaries and sweat glands both release
heat from the body
Excretion
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Sweat – releases toxins
Makes proteins and vitamin D
 Contains sensors to feel touch,
temperature, pain
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Structure of the Skin
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The skin is composed of two kinds of tissue:
The outer epidermis is made of stratified
squamous epithelium
 The underlying dermis is made up of
connective tissue
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The epidermis and dermis are firmly
connected.
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A burn or friction may cause them to separate
resulting in a blister.
Structure of the Skin
Deep to the dermis is the subcutaneous
tissue, or hypodermis, which is mostly
adipose tissue (fat).
 It is not considered part of the skin, but it
does protect the organs.
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absorbs shock and insulates the deeper
tissues from extreme temperature changes
Epidermis
The epidermis is composed of 5 layers
called strata.
 The epidermis has no blood supply of its
own, it is avascular.
 Most cells are keratin cells, which
produce keratin
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Keratin – fibrous protein that makes the
epidermis tough & protective
Epidermis
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Melanin – pigment that ranges in color
from yellow to brown to black
Produced by special cells called
melanocytes
 When the skin is exposed to sunlight, the
melanocytes produce more of the
melanin pigment and tanning occurs.
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Freckles and moles are seen where
melanin is concentrated in one spot.
Epidermis
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Excessive sun exposure eventually
damages the skin.
By causing the elastic fibers to clump,
leathery skin forms.
 It depresses the immune system.
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Overexposure to the sun can also
damage DNA of skin cells, which
leads to skin cancer.
Dermis
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The dermis is the strong, stretchy envelope that
holds the body together.
When you purchase leather goods, you are buying
the treated dermis of animals.
The dermis varies in thickness
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very thick on palms of hands and soles of the feet,
but is quite thin on the eyelids.
The dermis contains blood vessels, sweat and oil
glands, pressure receptors, touch receptors,
temperature receptors and pain receptors.
Dermis
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Collagen fibers are found throughout the dermis.
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They are responsible for the toughness of the dermis
and give the skin its elasticity.
The dermis is supplied with blood vessels that play a
role in maintaining body temperature.
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When body temperature is high, the capillaries become
swollen and the skin is reddened and warm. This
allows body heat to radiate from the skin surface.
If the environment is cool and body heat must be
conserved, blood bypasses the dermis capillaries
allowing the internal body temperature to remain
constant.
Appendages of the Skin
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The skin appendages include oil and sweat
glands, hairs and hair follicles, and nails.
Each of these appendages arises from the
epidermis and plays a role in maintaining
homeostasis.
Includes:
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Oil (Sebaceous) Glands
Sweat Glands
Hair and Hair Follicles
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Nails
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Sweat and Oil Glands
Sweat and oil glands are exocrine
glands (they secrete substances) that
release their secretions to the skin
surface through ducts.
 These glands reside in the dermis.
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Oil Glands
Oil glands are found all over the skin,
except on the palms of the hands and the
soles of the feet
 Their ducts usually empty into a hair
follicle, but some open directly onto the
skin surface.
 The product of the sebaceous glands is
called sebum.
 Sebum keeps the skin soft and moist
and keeps the hair from becoming brittle.
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Oil Glands
Sebum also contains chemicals that kill
bacteria, so it is important in preventing
the bacteria present on the skin surface
from invading deeper skin regions.
 if a sebaceous gland’s duct becomes
blocked by sebum, a whitehead appears
 if the accumulated material oxidizes and
dries, it darkens, forming a blackhead
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Sweat Glands
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Widely distributed in the skin
More than 2.5 million per person
2 types of sweat glands:
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Eccrine glands – more numerous and found
all over the body, produce sweat to regulate
body temperature and inhibit the growth of
bacteria present on the skin surface
Apocrine glands – larger than eccrine glands,
ducts empty into hair follicles, confined to the
axillary (armpit) and genital areas of the body
Hair and Hair Follicles
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Millions of hairs scattered all over the body
Hair is a flexible epithelial structure produced
by a hair follicle.
The part of the hair enclosed in the follicle is
called the root.
The part projecting from the surface of the scalp
or skin is called the shaft.
A hair is formed by division of the epithelial cells
in the growth zone, called the hair bulb, at the
bottom of the follicle.
Hair and Hair Follicles
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The bulk of the hair shaft, like most of the
epidermis, is dead material and almost entirely
keratinized protein.
Each hair consists of a central core called the
medulla.
The medulla is surrounded by a bulky cortex
layer.
The cortex is enclosed by the outermost cuticle.
Hair pigment is made by melanocytes in the
hair bulb, and varying amounts of different types
of melanin (yellow, rust, brown, black) combine
to produce all varieties of hair color from pale
blond to black.
Hair and Hair Follicles
Humans are born with as many hair
follicles as they will ever have.
 Hairs are among the fastest growing
tissues in the body.
 Hairs have muscles called arrector pili that
connect the hair follicle to the dermis.
 When these muscles contract, the hair is
pulled upright causing “goosebumps”.
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Nails
Scalelike modification of the epidermis, like
the hoof or claw of other animals
 Nails are mostly nonliving material, like
hairs.
 Nails are transparent and nearly colorless,
but they look pink because of the rich blood
supply in the underlying dermis.
 The white crescent in the nail is called the
lunula.
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• It is a thickened area of the nail.
Homeostatic Imbalances of
the Skin
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The skin is only about as thick as a paper
towel! But, when the skin is seriously
damaged, nearly every system in the body is
affected.
The skin can develop more than 1000
different disorders.
The most common skin disorders result from
allergies or bacterial, viral, or fungal
infections.
Less common problems are burns and skin
cancers, but these are also more serious.
Infections and Allergies
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Athlete’s foot: a fungus infection of the skin
on the foot, between the toes
Boils: inflammation of hair follicles and
sebaceous glands, common on the back of the
neck
Cold sores: small fluid-filled blisters on the
lips/mouth caused by herpes simplex (virus)
infection; the virus localizes in a nerve under
the skin where it remains inactive until fever,
UV radiation, or emotional upset
Infections and Allergies
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Dermatitis: itching, redness, and swelling of
the skin that results in blistering; caused by
exposure of the skin to chemicals that provoke
allergic reactions (such as poison ivy)
Impetigo: lesions that form around the mouth
and nose; caused by a highly contagious
bacterial infection
Psoriasis: a chronic condition that may be
hereditary; reddened lesions of the skin,
attacks are triggered by trauma, infection,
hormonal changes and stress
Burns
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A burn is tissue damage and cell death caused by
intense heat, electricity, UV radiation, or certain
chemicals (such as acids).
When the skin is burned, the cells are destroyed. 2
life threatening problems result:
 The body loses its supply of fluids because they seep
from the burned surfaces. This results in dehydration
and electrolyte imbalance. Fluids (including blood)
must be administered to the patient.
 Infection is the leading cause of death in burn victims
since pathogens, such as bacteria and fungi, easily
invade areas where the skin has been destroyed.
Burns
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To determine how
much of the body
surface is burned, the
rule of nines is used.
The body is divided
into 11 areas. Each
accounts for 9% of
the total body surface
area, plus 1% for the
genital region.
Burns
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Burns are classified according to the severity as
first, second, or third-degree burns.
In first-degree burns, only the epidermis is
damaged.
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the area becomes red and swollen, not usually
painful
ex. sunburn (usually)
Second-degree burns involve injury to the
epidermis and the upper region of the dermis.
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the skin is red and painful, blisters appear
regrowth of the epithelium can occur
Burns
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Third-degree burns destroy the entire
thickness of the skin
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also called full-thickness burns
burned areas appear blackened or graywhite in color
the burned area is not painful since the
nerve endings in the area are destroyed
regeneration is not possible, skin
grafting must be done cover the
underlying tissues
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Burns are considered critical if any of
these conditions exist:
• Over 25% of the body has 2nd degree burns
• Over 10% of the body has 3rd degree burns,
or
• There are 3rd degree burns of the face,
hands, or feet.
Skin Cancer
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Numerous types of tumors
Most are benign and do not spread
However, some skin tumors are malignant, or
cancerous, and they tend to invade other areas of
the body.
Skin cancer is the single most common type of
cancer in humans.
Most important risk factor – overexposure to
ultraviolet radiation
Frequent irritation of the skin by infections or
chemicals – also a predisposing factor for skin
cancer
3 Types of skin cancer
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Basal Cell Carcinoma – the least
malignant and most common skin cancer
Cancer lesions occur on sun-exposed
areas of the face
 Appear as shiny, dome-shaped nodules
that later develop a central ulcer with a
“pearly” beaded edge.
 Slow growing
 99% of cases are cured when lesion is
removed surgically.
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Squamous Cell Carcinoma
Most often on the scalp, ears, hands,
and lower lip
 Scaly, reddened, and round elevation
that forms an ulcer w/ a raised border
 Grows rapidly and may spread to the
lymph nodes if not removed.
 Also sun-induced
 Curable if treated early with surgery or
radiation.
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Malignant Melanoma
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Cancer of melanocytes
Melanoma accounts for only 5% of skin cancers.
However, its incidence is increasing rapidly and it
is often deadly.
Melanoma usually appears as a spreading brown
to black patch that spreads rapidly to surrounding
lymph nodes and blood vessels.
The chance for survival is about 50%.
Early detection helps to increase this chance.
Skin Cancer Detection
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ACS suggests that everyone examines skin for new
moles/spots, especially people who are frequently
exposed to the sun.
ABCD rule for recognizing melanoma.
Asymmetry – two sides of mole do not match
 Border irregularity – borders of the lesion are not
smooth
 Color – the spot contains areas of different colors
 Diameter – the spot is larger than 6mm in diameter
(pencil eraser)
http://www.cancer.org/docroot/lrn/lrn_0.asp
http://www.skincancer.org/
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