Study Guide for the
Integumentary System
Thursday, November 29, 2012
Integumentary System
Slap me some skin!
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Integumentary System
• The integumentary system consists of the skin, aka
cutaneous membrane, and its accessory structures:
glands, hair, nails, muscle and nerves
• It is made up of different types of tissue that perform
specific functions
• It is the heaviest organ with the largest surface area
• Approximately 640,000 sensory receptors connected to
the spinal cord
• An area of skin the size of a quarter contain roughly 3
million cells, 100 sweat glands, 50 nerve endings, and 3
feet of blood vessels
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The Biochemical/Physiological/Anatomical functions
of the skin: also discussed as “What does the Skin do
for Us?”
1. It helps our body control it internal and external temperature.
2. It is the first line of protection for our body. An intact skin keeps
foreign matter out.
3. It is the receiver of sensation through the sensory nerves that reside
in the skin.
4. It is involved in excretion . . . Sudoriferous glands assist in the release
of certain salts and waste products of the cells.
5. It contributes to our immune function as the pH of both sweat and
sebum are hostile to foreign organisms and their presence assists in
preventing hostile organisms from entering the body.
6. It is a reservoir for blood. About 8 to 10% of the blood in the body is
in the skin at any given time.
7. The skin is involved in the processing of Vitamin D, a Vitamin
necessary to health and well-being.
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Integumentary System
Structure of the skin
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The epidermis is the
superficial part of the skin
•
Deep to the epidermis is a
layer of connective tissue
called the dermis
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Glands, hair and nails
Deep to the dermis is the
subcutaneous layer
(hypodermis)
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Consists of loose connective tissue
and adipose tissue
This layer separates the skin from the
underlying muscle, bone, and other
structures
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Integumentary System
Epidermis
•
The most superficial layer of
the skin
•
Composed of stratified
squamous epithelium
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Separated from the dermis by
a basement membrane
•
Four types of skin cells in the
epidermis:
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Keratinocytes
Melanocytes
Merkel Cells
Langerhans cells
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Integumentary System
Epidermis
Keratinocytes
• Make up 90% of the epidermis
• Lie in many distinct layers and
produce a tough, fibrous protein
called keratin
• Keratin helps to protect the skin
from heat, microorganisms, and
chemicals
Melanocytes
• Pigment cells that are responsible
for the color of the skin
• Form 8% of all skin cells
• Manufacture melanin
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Integumentary System
Epidermis
Merkel Cells
• Specialized cells found
predominantly in skin of the digits,
lips and around hair follicles
• In close contact with touch
receptors and stimulate these
sensory nerves endings
Langerhans cells
• Type of immune cells involved in
defense mechanisms
• Form 2%-8% of the epidermal cells
• Protect the skin from pathogens
and destroy abnormal cells that
are present on the skin
• Play a role in allergic skin reactions
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Integumentary System
Epidermis
• For convenience, we
separate the epidermis
into five layers:
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Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum germinativum (or
basale)
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Integumentary System
Epidermis
Stratum Germinativum
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Single layer
Consists of cuboidal or columnar
epithelium
Attached to basement membrane
Its folds are known as epidermal
ridges and extend into the dermis
Dermal papillae are the ridges,
which form a pattern that can be
seen a whorls and loops in the
palms and soles of the hands and
feet
This layer contains germinative or
basal cells, which multiply rapidly
and replace cells in the superficial
layer
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Integumentary System
Epidermis
Stratum Spinosum
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Consists of 8 to 10 layers of cells
located immediately above the
stratum germinativum
These cells have a spiny
appearance, hence the name
As cells multiply in stratum
germinativum, they are pushed
upward in the stratum spinosum
Langerhans cells and keratinocytes
are located in this area
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Integumentary System
Epidermis
Stratum Granulosum
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Consists of three to five layers
Granular appearance when viewed
under a microscope
Contain a granular protein called
keratohyalin
Lamellar granules, which release a
lipid-rich secretion into spaces
between the cells to help slow the
loss of fluids, is also found here
As cells manufacture keratohyalin,
they become flatter and thinner
Cell membranes become thicker
and impermeable to water
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Integumentary System
Epidermis
Stratum Lucidum
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Translucent in color
Consist of densely packed, flat cells
that are filled with keratin
More prominent in the palms of the
hands and soles of the feet
Stratum Corneum
• Most superficial layer
• Consist mostly of dead cells and
keratin
• Keratinization/cornification – the
transformation from live cells to dead
cells in the epidermis
• 15 to 30 layers of cells
• 15-30 from germinativum to
corneum
• Cells remain in stratum corneum for
2 week before being shed
• Excessive friction of this layer
thickens up and forms calluses
• About 500mL of water per day is lost
via the skin
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Integumentary System
Dermis
• The dermis is the
connective tissue layer that
lies deep to the epidermis
• Accessory structures (sweat
glands and hair follicles) are
located in the dermis.
• It contains a network of
blood vessels, nerve
endings, and nerves
• We can divide the dermis
into two layer:
• Papillary layer
• Reticular layer
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Integumentary System
Dermis
• The collagen and elastic fibers
in the dermis impart strength,
elasticity, and extensibility of
the skin
• The consistency and texture of
the skin is due to water
content and these fibers
• The water content helps
maintain the flexible and
resilient properties of the skin,
or skin turgor
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Integumentary System
Dermis
Lines of Cleavage In the Skin
• This is the pattern of the
collagen and elastic fibers
bundles
• It denotes the lines of tension
in the skin
• It also denotes crease lines and
the direction in which the skin
will stretch the most
• Important for MTs as we
manipulate the structures of
the skin and its underlying
structures through these
patterns.
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Integumentary System
Subcutaneous
• The subcutaneous or
hypodermis lies deep to the
dermis
• It is largely composed of
connective tissue interwoven
with the connective tissue of
the dermis
• This layer stabilizes the skin,
yet allows for a little
movement
• The subcutaneous layer
separates the skin from the
deep fascia that surrounds
muscles and organs
• The subcutaneous layer can
also be called superficial fascia
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Integumentary System
Nerve Supply
• The blood vessels and glands in
the skin are supplied by
autonomic nerves
• In addition, there are a vast
number of sensory receptors
that respond to:
• Touch
• Pressure
• Pain
• Cold
• Heat
• There are more receptors
present in areas that are more
sensitive to sensations, like the
face, lips and fingers
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Integumentary System
Nerve Supply
• The sensory nerves from a specific
area of the skin enter a particular
segment of the spinal cord
• The area of skin supplied by the
nerves from a particular spinal
segment is known as the
dermatome of that segment
• Damage to a spinal nerve results in
loss of sensation in its specific
dermatome
• Each part of the body is mapped
out in the area of the brain that
perceives sensations
• Many consider the skin an
extension of the brain that allows
the mind to interact with the
physical world through touch
• During prenatal development, both
the skin and the nervous system
are derived from the same
embryonic layer (ectoderm)
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Integumentary System
Blood Circulation
• 8% to 10% of the total blood flow in
the body can be found in the skin
• Heat loss from the body is
regulated by the alternation of the
volume of blood in the skin
• The arteries supplying the skin
form a network where the
subcutaneous layer meets the
dermis, known as the cutaneous
plexus
• Branches from these arteries
supply the adipose tissue located in
the subcutaneous layer
• These branches form another
network where the dermis meets
the epidermis, known as the
papillary plexus
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Integumentary System
Functions of the Skin
• Protecting the underlying
organs and tissues from
damage
• Excreting items like salt, water
and organic wastes that are
lost through sweat
• Maintaining body temperature
• Detecting changes in the
surrounding environment with
its sensory receptors
• Synthesizing vitamin D
• Store nutrients
• Acting as a reservoir of blood
in case it needs to be diverted
for systemic needs
• Its most important function is
to reflect emotional states,
regardless of disease
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Integumentary System
Functions of the Skin
Protection
• The skin protects the internal
organs and other structures of the
body from environmental factors,
most commonly UV radiation
• Melanin protects the skin from
sunburn
• UV radiation exposure can damage
fibroblasts located in the dermis
• This leads to faulty
manufacturing of connective
tissue and wrinkling of the
skin
Temperature Regulation
• The extremities are cooler than the
rest of the body
• In general, body temperature must
be within a narrow range
• Proper enzyme function is
dependant on the body’s ability to
maintain this narrow temperature
range
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Integumentary System
Functions of the Skin
Absorption
• The skin can absorb or excrete
certain substances
• Vitamin D synthesized in the skin
is transported to the liver and
then to the kidneys
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Vitamin D increases calcium
absorption in the intestines
and is an important hormone in
calcium metabolism
A lack of vitamin D can lead to
rickets in children and
osteomalacia in adults
• Substances that are also lipidsoluble can penetrate the
epidermis, therefore allowing for
a slower absorption rate
• Systemic adverse effect can be
produced if drugs are
transmitted transdermally for
prolonged periods
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Integumentary System
Skin Color
• Changes in skin color may indicate
health problems or other
circumstances
• Melanocytes contain the enzymes
required for converting the amino acid
tyrosine into melanin
• The pigment melanin is then packaged
inside the cell in smell vesicles called
melanosomes
• They are then transferred along the
processes that extend into the
superficial layers of the skin
• In the superficial layers, the vesicles
are transferred into other cells,
coloring them temporarily
• They eventually fuse with lysosomes
are then destroyed
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Integumentary System correction undelined below
Skin Color
Effects of Blood Flow on Skin Color
• The color of skin is a result of the
oxygenated hemoglobin in the red
blood cells
• When blood flow is reduced
temporarily , the skin becomes pale
• When pressure is applied to the
skin, the blood in the vessels of
that area stagnates
• Oxygen in the hemoglobin is used
by the tissue and the hemoglobin
becomes darker as a result of
deoxyhemoglobin formation,
visually a bluish hue called cyanosis
• It is more prominent in the lips,
tongue, conjunctiva, and beneath
the nails
• When exposed to the cold, the
blood vessels constrict to conserve
heat
• When exposed to heat, the blood
vessels dilate to dissipate heat
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Integumentary System
Accessory Structures
• Glands of the integumentary
system include:
• Sweat glands
• Sebacous glands
• Ceruminous glands
Sweat glands
• Also known as sudoriferous glands,
are coiled tubular glands that are
surrounded by a network of
capillaries
• Located in the dermis
• They discharge secretions directly
on the surface of the skin or the
hair follicles
• Sweat is 99% water, the rest 1% is
sodium chloride, electrolytes, lactic
acid, some nutrients, and waste
products
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Integumentary System
Accessory Structures
Sweat glands
• Most of the skin’s sweat glands
are eccrine sweat glands
• They are located over the
entire body—approx. 2 to 5
million
• The highest concentration lies
in the forehead, palms and
soles of the feet
• There are also apocrine sweat
glands, which are located in
the armpits, around the
nipples, the beard area and in
the groin
• These glands do not
become active until
puberty, when they
secrete a cloudy, sticky
secretion with a
characteristic odor
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Integumentary System
Accessory Structures
Sebaceous glands
• These are located close to hair
follicles and discharge their
secretions onto these follicles
• In other areas, they discharge onto
the skin surface
• They secrete an oily substance and
are often called the oil glands
• Sebum is a mixture of lipids,
proteins, and electrolytes
• Sebum does several things:
• Provides lubrication
• Protects the keratin of hair
• Conditions the skin
• Prevents the excess
evaporation of water
• Acne is a result of the blockage of
the sebaceous ducts and
inflammation of the glands and
surrounding area
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Integumentary System
Accessory Structures
Ceruminous Glands
• Ceruminous glands, which are
specialized, lie in the external
auditory canal
• Modified sweat glands, they
secrete cerumen or earwax
• Earwax protects the ear from
foreign particles
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Integumentary System
Mammary Glands
• Mammary glands are the glandular
tissue of the breast
• They are modified
sudoriferous/sweat glands
• The breasts are largely made up of
fat and connective tissue, scattered
with immature glands
• During pregnancy, hormones
enlarge the glands, which then
occupy a major portion of the
breast
• Each gland consists of 15 to 20
compartments (lobes) which are
separated by fat tissue
• Each lobe has many smaller
compartments called lobules
• Alveoli are the milk-secreting
glands in the breast
• The alveoli open into larger ducts,
eventually coming out through the
nipple
• Surrounding the nipple is a circular
pigmented area known as the
areola
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Integumentary System
Accessory Structures
Hair
• Hair is found in the skin almost all
over the body
• It originates in the hair follicles, which
is found in the dermis
• Hair is made up of soft and hard
keratin-giving it texture and color
• The hair bulb contains a network of
capillaries and nerves
• A strip of smooth muscle, the arrector
pili muscle, extends from the upper
part of the dermis to connective
tissue surrounding the hair
• Two types of hair in the body:
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Vellus hair: fine and fuzzy
Terminal hair: deeply pigmented
Nails
• The body of a nail is composed of
dead cells that are packed with keratin
• The nail protects the tips of fingers
and toes
• Nail beds are formed at the nail root,
an epithelial fold deeply located near
the periosteum of the bones
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How does the skin react to
inflammation?
• Inflammation is the reaction of living tissue to
injury and is easily seen on the surface of the
skin
• Inflammation helps to heal wounds and
prevents and combats infection by helping the
body adapt to stressors
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Integumentary System
Inflammation
• White blood cells are triggered into
action
• Immediately after the injury, they
accumulate along the blood vessel
walls, known as margination or
pavementing
• The next stage is emigration: the
wbc’s squeeze through the
widening gap between the cells of
the capillary wall
• They then reach the injured region
• Chemotaxis is the process by which
the wbc’s are attracted to this
region
• On reaching the site, they destroy
the cells and other structures that
are deemed foreign, known as
phagocytosis
• A phagosome is formed
when the injured tissue is
surrounded and taken into
the cytoplasm of the
phagocyte
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Integumentary System
Inflammation
Causes of Inflammation
• Physical
• Burns
• Extreme cold
• Trauma
• Chemical
• Poisons, either acid or
organic
• Infection
• Bacteria
• Viruses
• Fungi
• Parasites
• Immunologic circumstances
• Vascular or hormone
disturbances
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Video 1
Video 2
Video 3
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Effects of massage on the Integument
• Massage can help realign collagen fibers in the
dermis during and after healing of deep skin
wounds.
• Massage can increase blood flow locally and
facilitate the removal of toxins released by
injured tissue and speed up healing.
• Massage will also speed up the absorption of
drug near the injection site.
• Massage can reduce pain perceived by the brain.
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