INTEGUMENTARY
SYSTEM
INTRODUCTION
The integumentary system is made up of the
skin, hair, nails, and various glands
- when something goes wrong with your skin, it
is apparent right away
- physicians pay attention to the skin because any
changes could be signs of a disorder or
problem with another body system
STRUCTURE AND FUNCTION
The integument has 2 major components:
1. CUTANEOUS MEMBRANE- or skin; an
organ composed of the EPIDERMIS
(superficial epithelium) and underlying
connective tissues of the DERMIS
2. ACCESSORY STRUCTURES- include hair,
nails, and a variety of exocrine glands
- below the dermis is the SUBCUTANEOUS
LAYER, which attaches integument to deeper
structures (muscle and bone)
There are 5 major functions of the integument:
1. Protection- skin protects underlying tissue and
organs from impact, chemicals, infection;
prevents loss of body fluids
2. Temperature maintenance- skin regulates
heat gain or loss to environment
3. Making and storing of nutrients- epidermis
makes vitamin D, which aids in uptake of
calcium; dermis contains large amounts of
lipids (fats) in adipose tissue
4. Sensory reception- receptors detect pain,
pressure, and temperature stimuli and relay
that info. to the nervous system
5. Excretion and secretion- excretes salts, water,
organic wastes; produces milk
EPIDERMIS
The EPIDERMIS consists of stratified squamous
epithelium
- WHAT DOES STRATIFIED MEAN?
- in THICK SKIN (palms of hands and soles of
feet) there are 5 layers
- in THIN SKIN (covers rest of body) there
are only 4 layers
STRATA OF EPIDERMIS
STRATA IS ANOTHER NAME FOR LAYERS
In order from the basement membrane toward
the surface are:
Stratum germinativum
Intermediate strata (3 layers)
Stratum corneum
STRATUM GERMINATIVUM
- deepest epidermal layer
- attached to basement membrane by a type of
desmosome
- basement membrane separates the
epidermis from the dermis
- this layer forms EPIDERMAL RIDGES which
extend into the dermis, increasing area of
contact between the 2 regions
- contours of the skin follow these ridge
patterns
- these ridges in the palms and soles increase
surface area of the skin, and help ensure grip
Ridge patterns are GENETICALLY
DETERMINED, and do not change over a
lifetime
   FINGERPRINTS!
You also find large stem cells (germinative cells)
in the stratum germinativum, so this is the
layer where new cells are generated and begin
to grow
- these cells replace those lost or shed at the
surface
- also contains MELANOCYTES- receptors
provide info. about objects touching the skin;
make MELANIN- a pigment that colors the
epidermis
INTERMEDIATE STRATA
- made up of 3 layers; each becoming specialized
to form outer protective covering of skin
- find the protein KERATIN here:
* extremely durable and water-resistant
* coats the surface of the skin, forms basic
structure of hair, calluses, and nails
STRATUM CORNEUM
- outermost layer
- consists of 15-30 layers of flattened, dead
epithelial cells that have large amounts of
keratin  these cells are said to be
KERATINIZED
- dead cells in each layer are tightly connected
by desmosomes  are usually shed in sheets
rather than individually
TIMELINE
It takes about 2-4 weeks for a cell to move from
the stratum germinativum to the stratum
corneum
- cell is removed from its oxygen and nutrient
supply, is filled with keratin, and finally dies
- dead cells usually remain in the stratum
corneum for about 2 weeks before they are
shed
- as these layers are lost, they are replaced from
below
SKIN COLOR
Skin color is caused by interaction between:
1. epidermal pigments
2. dermal blood supply
PIGMENTATION
The epidermis has varying amounts of the two
pigments CAROTENE and MELANIN
CAROTENE- orange-yellow pigment that
normally accumulates in dermal cells
- these pigments are found in vegetables such as
carrots (eating a large amount of carrots can
turn your skin orange!)
- can be converted to vitamin A which is required
for normal maintenance of epithelial tissue
MELANIN- brown, yellow-brown, or black
pigment produced by melanocytes
- melanocytes make and store melanin and inject
it into the epithelial cells of the stratum
germinativum and intermediate strata
- this colors the entire epidermis
Melanocyte activity increases after sunlight
exposure
FRECKLES- represent areas of larger-thanaverage melanin production
- most abundant on surfaces exposed to sun
ULTRAVIOLET (UV)
RADIATION
A small amount of UV radiation is beneficial
because it stimulates the making of vitamin D3
- too much UV radiation produces burns
- melanin helps to prevent skin damage by
absorbing UV radiation before it can reach the
deep layers of the integument
- despite this protection, long-term damage
can result, even in individuals with dark
skin
EFFECTS OF UV EXPOSURE:
- alterations in underlying connective tissue can
cause premature wrinkling
- skin cancers can result from chromosomal
damage to stem cells
* one major consequence of depletion of the
ozone layer has been an increase in rates of
skin cancer
* WEAR SPF OF AT LEAST 15; HIGHER
FOR BLONDES AND REDHEADS
DIFFERENCES IN SKIN
COLOR
Differences in skin color between individuals is
not due to the number of melanocytes, but to
the different levels of melanin production
- in the inherited condition albinism melanin
is not produced by melanocytes
DERMAL CIRCULATION
- Blood having a lot of oxygen is bright red, and
blood vessels in the dermis give the skin a
reddish tint that is most obvious in lightskinned individuals
- when vessels are dilated (during
inflammation), red tones become more
pronounced
- when vessels are constricted (frightened), skin
becomes pale
- during a prolonged reduction in circulation,
blood loses oxygen and becomes dark red, then
blue  CYANOSIS
VITAMIN D3
Limited exposure to the sun is beneficial:
- epidermal cells in stratum germinativum
and intermediate strata convert a steroid
into VITAMIN D3
- this is modified and converted into a hormone
called CALCITRIOL which is essential for the
absorption of calcium and phosphorus by the
small intestine
- deficiency of vitamin D3 causes abnormal
bone growth
SKIN CANCER
BASAL CELL CARCINOMA- malignant cancer
that originates in the stratum germinativum
- most common type
SQUAMOUS CELL CARCINOMAS- less
common
- metastasis seldom occurs in either; survival
is good
MELANOMAS- seldom-occurring and lifethreatening
- usually begin from moles, but may appear
anywhere in the body
- can grow rapidly and metastasize through
the lymphatic system
- survival depends on when condition is detected
and treated
- AVOIDING UV RADIATION CAN
PREVENT ALL 3 TYPES OF CANCER
The Dermis
The Dermis
The dermis lies below the epidermis and has 2
main components:
Papillary layer
Reticular layer
PAPILLARY LAYER
- consists of loose connective tissue that supports
and nourishes the epidermis
- contains capillaries and nerves supplying the
surface of the skin
RETICULAR LAYER
- deeper layer
- consists of interwoven meshwork of dense,
irregular connective tissue
- boundary between reticular and papillary
layers is indistinct
- collagen fibers of reticular layer extend into the
subcutaneous layer
- reticular layer provides support and
attachment for dermis while allowing
flexibility
OTHER DERMAL
COMPONENTS
The dermis contains all of the cells found in
connective tissue proper (macrophages,
fibroblasts, etc)
- accessory organs such as hair follicles and
sweat glands extend into the dermis
- other systems communicate with the skin
through the dermis
Ex: reticular and papillary layers contain blood
vessels, lymph vessels, and nerve fibers
- blood vessels provide nutrients and
oxygen, and remove CO2 and wastes
- blood and lymph vessels help local tissues
defend and repair themselves after injury or
infection
- nerve fibers control blood flow, adjust gland
secretion rates, and monitor nerve receptors
The Subcutaneous Layer
Subcutaneous Fat
The dermis is connected to the subcutaneous
layer by an extensive network of connective
tissue fibers
- the subcutaneous layer is not actually part of
the integument, but is important in stabilizing
position of the skin in relation to underlying
tissue
- this layer contains many fat cells (adipose)
- these adipose cells provide infants and small
children with a layer of “baby fat” which reduces
heat loss, and acts as a shock absorber to prevent
injury
- as we age, we accumulate this fat in different places:
* Men- around neck, upper arms, lower back,
buttocks
* Women- breasts, buttocks, hips, thighs
* Both accumulate in abdominal area
- the subcutaneous layer is very elastic, has large
blood vessels, and contains no vital organs
Accessory Structures
HAIR FOLLICLES
Hair covers the body almost everywhere
EXCEPT:
Sides and soles of feet
Palms
Sides of fingers and toes
Lips
STRUCTURE OF HAIR
- hair follicles project into the dermis and often
into the subcutaneous layer
- walls of each follicle contain all the cell layers
found in epidermis
- the epithelium at the base of a follicle
surrounds the HAIR PAPILLA- a peg of
connective tissue containing capillaries and
nerves
- hair is formed by the repeated divisions of
epithelial stem cells surrounding the papilla
- as daughter cells are pushed to the surface, the
hair lengthens and the cells become keratinized
and die
- the point at which this occurs marks the
boundary of the HAIR ROOT and HAIR
SHAFT
- hairs grow and are shed according to a HAIR
GROWTH CYCLE based on the activity of
hair follicles
- generally, a hair in the scalp grows from 2 to 5
years at a rate of about 0.3 mm per day, and
then its follicle may become inactive for some
time
- when another growth cycle begins, the old
hair is pushed toward the surface to be shed
- differences in hair length between individuals
depends on variations in growth rate and in the
length of the hair growth cycle
- other differences in hair appearance result from
size of follicles and shape of hairs
FUNCTIONS OF HAIR
- there are approximately 5 million hairs on the
human body
- the 100,000 hairs on the head protect the
scalp from UV light, cushion a light blow to
the head, and insulate the skull
- hairs guarding the entrance to the nostrils and
ears, as well as the eyelashes, defend against
entry of foreign particles and insects
- each hair follicle as a sensory nerve associated
with it  you can feel a single hair move :
early warning system
- smooth muscles called ARRECTOR PILI
MUSCLES are connected to the hair follicle
- when stimulated, they pull on follicle and cause
hair to stand up- “goose bumps”
HAIR COLOR
- hair color depends on differences in type and
amount of pigment produced by melanocytes
in the papilla
- color is genetically determined
- color may also be influenced by hormonal or
environmental changes
Ex: pigment production decreases with age,
and color of hair lightens
- white hair results from lack of pigment,
and the presence of air bubbles in the hair
shaft
- as number of white hairs increases,
individual’s color is described as GRAY
- on average, about 50 hairs are lost from the
head per day
SEBACEOUS GLANDS
Sebaceous glands are a type of exocrine gland
that discharge a waxy secretion into hair
follicles and onto the skin
- contraction of arrector pili muscles squeezes
the sebaceous glands, forcing the secretions
into the hair follicles and onto the surrounding
skin
- the secretion is called SEBUM- it lubricates
the hair and inhibits growth of bacteria
Sebaceous glands are very sensitive to changes
in concentrations of sex hormones
- secretions increase at puberty
- an individual with large sebaceous glands
may be prone to ACNE
- in acne, sebaceous glands become blocked and
secretions accumulate causing pimples to form
SWEAT GLANDS
The skin contains 2 types of sweat glands:
Apocrine sweat glands
Merocrine sweat glands
APOCRINE GLANDS
- secrete their products into hair follicles in the
armpits, around the nipples, and in the groin
- at puberty, these glands begin discharging a
sticky, cloudy secretion that becomes odorous
when broken down by bacteria
- antiperspirant works by contracting the
sweat gland openings and decreasing the
quantity of secretions
MEROCRINE GLANDS
- far more numerous than apocrine glands
- the skin of an adult contains 2-5 million
merocrine glands
- palms and soles have the highest number
- merocrine glands are coiled tubular glands that
discharge their secretions directly onto the
surface of the skin
- secretions are called PERSPIRATION- cool
the surface of the skin and reduce body
temperature
When a person sweats in the hot sun, all
merocrine glands are working together:
- blood vessels beneath the epidermis are flushed
with blood- skin becomes red
- skin surface is warm and wet, and as the
moisture evaporates, the skin cools
- if body temperature falls too low, perspiration
stops, blood flow to the skin decreases, and the
cool, dry surfaces release little heat to the
environment
SWEAT IS 99% WATER
- but also contains salts, organic nutrients, and
waste products such as urea
- is what gives sweat a salty taste
- when all merocrine glands are working
together, perspiration can exceed 1 gallon per
hour
- you must drink fluids to replenish this loss
OTHER TYPES OF SWEAT GLANDS:
- mammary glands produce milk
- ceruminous glands in the ear produce ear
wax
NAILS
Nails form on dorsal surface of fingers and toes,
and protect the exposed tips and help limit
their distortion when they are subjected to
mechanical stress
STRUCTURE
- visible NAIL BODY made up of a mass of
dead, keratinized cells
- it extends below the surrounding epithelium
- nail body covers an area of epidermis called the
NAIL BED
- nail production occurs at the NAIL ROOT- an
epithelial fold that you cannot see from the
surface
- a portion of the stratum corneum extends over
the exposed nail nearest the root, forming the
CUTICLE
- underlying blood vessels give nails their pink
color
-
-
vessels may be obscured near the root,
leaving a pale crescent known as the
LUNULA
nail structure
CONTROL OF
HOMEOSTASIS
The integumentary system can respond directly
and indirectly to many local influences or
stimuli
Ex: when skin is subjected to mechanical
stresses, stem cells in the stratum
germinativum divide more rapidly to increase
the thickness of the epithelium 
CALLUSES FORM
INJURY AND REPAIR
Skin can regenerate because stem cells are
present in epithelial and connective tissue
components
- speed and effectiveness of skin repair depends
on the type of wound
* an INCISION (slender, straight cut) may
heal quickly
* an ABRASION (scrape) may take longer
to heal because it involves a greater area
4 STAGES OF SKIN
REGENERATION
1. When damage extends though epidermis and
into the dermis, bleeding occurs
2. Blood clot or SCAB that forms temporarily
restricts the entry of additional
microorganisms
- clot is made up of protein called FIBRIN
- cells of stratum germinativum rapidly divide
and migrate along sides of the wound to
replace missing epidermal cells
- phagocytes patrol damaged area and clear
away debris and pathogens
3. Dermal repairs must occur before epithelial
cells can cover the surface
- fibroblasts and connective tissue stem cells
divide to produce mobile cells that invade
deeper areas of injury
- capillaries follow the fibroblasts, providing a
circulatory supply
- combination of blood clots, fibroblasts, and
capillary network is called GRANULATION
TISSUE
- over time, the clot dissolves and number of
capillaries decreases
- fibroblast activity leads to formation of
collagen fibers and ground substance
4. Scar tissue is formed
- dermis will contain many collagen fibers and
few blood vessels
- damaged hair follicles, glands, muscle cells,
and nerves are seldom repaired
BURNS
Burns result from exposure of skin to heat,
radiation, electrical shock, or strong chemical
agents
- severity reflects depth of penetration and total
area affected
FIRST-DEGREE BURN
- superficial cells of epithelium are killed
- deeper areas of the epidermis and papillary
dermis are injured
- area appears inflamed and is tender
SECOND-DEGREE BURN
- superficial and deeper cells of epidermis are
killed; dermis may be affected
- reticular layer of epidermis may be injured, but
most accessory structures are unaffected
- blisters are present; very painful
THIRD-DEGREE BURN
- all epidermal and dermal cells are killed
- subcutaneous layer and deeper tissues and
organs are injured
- skin is charred; individual has no sensation
at all
AGING
SOME CHANGES THAT OCCUR WITH
AGING:
1. Skin injuries and infections become more
common- epidermis thins
2. Sensitivity of immune system reducedimmune cells are decreasing in number
3. Muscles become weaker, bone strength
decreases- decline in vitamin D3 production
4. Sensitivity to sun exposure increases- less
melanin produced
5. Skin becomes dry and scaly- sebum and
perspiration production decreases
6. Hair thins and color changes- follicles stop
functioning; again decreased melanin
production
7. Sagging and wrinkling of skin- dermis
becomes thinner and elastic fiber network
decreases
8. Ability to lose heat decreases- blood supply to
dermis is reduced; sweat glands become less
active
- more prone to overheating
9. Skin repairs slowly