UNIT II: THE INTEGUMENTARY SYSTEM - LAB
OUTLINE
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
OVERVIEW
ANATOMY OF THE SKIN, HAIR, AND NAILS
THE SKIN
A. Epidermis: 4 or 5 Layers
1. Layers of Cells in the
Epidermis
2. Thick and Thin Skin
3. Cells of the Epidermis
B. Dermis
1. Two Tissue Layers
2. Subcutaneous Tissue
3. Fibers
4. Nutrition
5. Nerve Endings
GLANDS
A. Major Glands of the Skin
1. Types of Sweat Glands
2. Other Glands
HAIR
A. Hair Structure
1. Hair Follicle
B. Three Types of Hair
C. Hair Color and Texture
D. Hair Growth
1. Hair Growth Follicle
NAILS
PHYSIOLOGY OF THE INTEGUMENTARY SYSTEM
A. Functions of the Skin
B. Injuries to the Skin
C. Diagnostic Tests used to Diagnose
Integumentary System Disorders
D. Integumentary System Disorders
1. Disorders
ADDITIONAL REPRESENTATIVE DISEASES AND
DISORDERS OF THE INTEGUMENTARY SYSTEM
●
damage from abrasion on the skin’s
surface
■ reduces water loss through the skin
○ Deep layer: dermis
■ Loose/areolar connective tissue
over dense irregular connective
tissue
■ responsible for most of the strength
of the skin
The hypodermis is adipose connective tissue; it is
not part of the skin, but it attaches the skin to the body
(muscle or bone)
○ Subcutaneous tissue, a layer of loose
connective tissue
THE SKIN
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In the adult human body, the skin makes up about
16% of the body weight and covers an area of
1.5-2m2.
Largest organ system in the human body.
Protects the inner organ, in need of daily care and
protection to maintain its health.
The skin’s primary role is to help protect the rest of
the body’s tissues and organs from physical damage
(such as abrasions), chemical damage (such as
detergent), and biological (such as microorganism).
Cutaneous membrane - Is the technical term for the
skin.
Made up of 3 general layers:
● Epidermis
○ Contains cells that produce pigment
and protect immune system
● Dermis
○ Contains nerve endings oil and
sweat glands, and hair follicles
● Subcutaneous layer/hypodermis
○ Made up of fat, connective tissue
and larger blood vessels
Accessory structures:
● Hair
● Gland
● Nails
OVERVIEW
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The integumentary system is composed of the skin,
hair, nails, and cutaneous glands.
its appearance can also indicate physiological
imbalances not just for vanity’s sake
ANATOMY OF THE SKIN, HAIR, AND NAILS
●
The skin is the largest organ of the body.
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It is composed of two layers:
○ Superficial layer: epidermis
■ Stratified squamous epithelial tissue
■ multiple cell layers of the epidermis
protects against the potential
Fig. Skin anatomy
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
EPIDERMIS: 4 OR 5 LAYERS
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Stratified squamous epithelium (multiple layers of
cube-shaped cells in the basal layer and
progressively flattened toward the surface).
○ Though the epidermis is stratified, it is not as
thick as the dermis.
○ The Epithelium can be non-keratinized
(moist) or keratinized.
■ Non-keratinized - the surface cells
retain new clues and are attached
to the cytoplasm.
■ Keratinized - the cytoplasm at the
surface is replaced by a protein
called “keratin”, and the cells are
dead. It is separated from the
underlying dermis by the basement
of the membrane.
● Called “keratinocytes”
● It makes cells durable. It is
the
durability
of
the
keratinocytes that gives the
epidermis its ability to resist
abrasion and reduce water
loss.
Other cells in epidermis: melanocytes, Langerhans
cells, and Merkel cells
○ Melanocytes produce the pigment melanin,
which contributes to skin color.
○ Langerhans cells are part of the immune
system.
○ Merkel cells are specialized epidermal cells
associated
with
the
nerve endings
responsible for detecting light touch and
superficial pressure.
Contains no blood vessels
○ The living cells of the dermis receive
nutrients and excrete waste products by the
diffusion of the substances between the
epidermis and the capillaries of the dermis.
4-5 strata (regions) (stratum: singular)
○ The number of strata of the skin varies
depending on the location in the body.
Fig. Layers of the epidermis
LAYERS OF CELLS IN THE EPIDERMIS
Stratum basale/germinativum
● simple cuboidal epithelial tissue.
● The deepest stratum of the epidermis
● A single layer of simple cuboidal or columnar
epithelial cells.
○ Actively divides to make new epidermis
○ Deepest layer of the epidermis
● So cells have structures that hold them to on another
or
to
the
basement
membrane
by
hemidesmosomes; while desmosomes hold the
keratinocytes together
○ The
connections
formed
by
the
hemidesmosomes and desmosomes provide
structural strength to the epidermis.
○ Keratinocytes are strengthened internally by
keratin fibers (intermediate filaments) that
insert into the desmosomes
● Functions:
○ Mechanically bind the cells together.
○ Help form a permeability barrier.
○ Provide a mechanism for intercellular
communications.
● Keratinocyte stem cells of the stratum basale undergo
mitotic divisions approximately every 19 days.
○ One (1) daughter cell remains a stem cell in
the stratum basale and divides again.
○ But other daughter cells are pushed toward
the surface and become keratinized.
○ It takes approximately 50-56 days for the cell
to reach the epidermal surface and will cast
off.
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
Stratum spinosum
● superficial to the basale
● Consists of 8-10 layers of many-sided cells
○ The cells of this stratum are pushed to the
surface, they flatten, then the desmosomes
break apart and new desmosomes are
formed. This particular desmosome is an
epithelial cell that has cell surface
glycoprotein which attaches to other
glycoproteins located on adjacent cells and
on the basement membrane. Among these
glycoprotein connections between cells,
there are some relatively strong adhesive
structures called “desmosomes”.
○ Desmosomes - consist of adhesive
glycoproteins that bind cells together and
intracellular proteins attached to the
immediate filaments that extend in the
cytoplasm of the cells. Many desmosomes
are found in the epithelial tissues that are
subjected to stress such as of the stratified
squamous epithelium of the skin. They hold
the keratinocytes together.
○ Hemidesmosome - similar to the one-half of
the desmosomes attached to the epithelial
cells to the basement membrane. During this
preparation for microscopic observation, the
cells usually shrink from one another except
where they are attached by desmosomes
causing the cells to appear spiny, hence the
name Stratum Spinosum.
● During preparation for microscopic observation, the
cells usually shrink from one another, except where
they are attached by desmosomes, causing the cells
to appear spiny—hence the name stratum spinosum.
● As keratinocytes progressed through this stratum
additional
keratin
fiber
and
lipid
defiled
membrane-bound organelles known as the Lamellar
bodies formed inside the cells.
Stratum granulosum
● Consists of 2-5 layers of somewhat flattened,
diamond-shaped cells.
● The long access of these cells is oriented parallel to
the surface of the skin.
● So this stratum derived its name from the presence of
protein granules of Keratohyalin which accumulate in
the cytoplasm of the keratinocytes. The lamellar
bodies which formed as the cells pass through the
stratum Spinosum move to the plasma membrane,
and release their lipid contents into the extracellular
space.
● Inside the keratinocyte, a protein envelope formed
beneath the plasma membrane. So in the most
superficial layers of the stratum granulosum, the new
clues and other organelles degenerate and the
keratinocytes die. Unlike other organelles, the keratin
fibers and keratohyalin granules within the cytoplasms
do not degenerate.
Stratum lucidum
● Found only in thick skin
● Is a thin, clear zone above the stratum granulosum,
found only in thick skin
● Consists of several layers of dead keratinocytes with
indistinct boundaries.
○ so the keratin fibers are present but the
keratohyalin which was evident has
dispersed around the keratin fiber and the
cells appear somewhat transparent.
● The stratum lucidum is present only in a few areas of
the body.
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
THICK AND THIN SKIN
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Stratum corneum
● composed of dead, keratin-filled cells that flake off
(exfoliate)
● The last and most superficial stratum of the
epidermis is the stratum corneum.
● Composed of 25 or more layers of dead
overlapping squamous cells joined by the
desmosomes.
○ Eventually, the desmosomes break apart,
and the cells are shed from the surface of
the skin.
■ Excessive shedding of the stratum
corneum of the scalp results in
dandruff.
■ Skin cells are continually shed from
other areas as others rub against
the body or as the skin is washed.
● Consist of cornified cells which are dead
keratinocytes with a hard protein envelope and filled
with protein keratin
○ Keratin: mixture of keratin fibers and
keratohyalin.
○ The envelope and keratin are responsible for
the structural strength of the stratum
corneum.
● The type of keratin found in that skin is soft keratin.
● Another type of keratin is hard keratin, which can be
found in nails and the external part of the hair.
○ Cells containing hard keratin are more
durable than cells with soft keratin, and they
are not shed off.
● Lipids are released from the lamellar bodies
surrounding the skin cells.
○ Lipids are responsible for many of the skin’s
permeability characteristics.
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Skin is characterized as thick or thin based on the
structure of the epidermis.
THICK SKIN - has all 5 epithelial strata
○ Can be found in areas subject to the
pressure of friction such as the palm of the
hands, soles of the feet, and the fingertips.
THIN SKIN - covers the rest of the body and is more
flexible than the thick skin. The stratum lucidum is
generally absent in the thin skin.
○ Each stratum in the thin skin contains fewer
layers of cells than found in the thick skin.
○ Example:
Stratum
granulosum
frequently
consists of only 1 or 2 layers of cells, than the 3-5
layers of cells in thick skin.
○ Hair can only be found in thin skin.
The entire skin (both the epidermis and dermis) varies
in thickness from 0.5 mm on eyelids to 5mm on the
back of the shoulders.
The term “thick and skin” only refers to the
epidermis and should not be used when total skin
thickness is considered.
○ It is actually the variation in the thickness of the
dermis that accounts for most of the difference in
total thickness.
■ For example, the skin of the back is thin,
whereas that of the palm of the hand is
thick skin. However, because the dermis of
the skin of the back is greater than that of
the palm.
If the skin is subjected to friction or pressure, an area
called “Calluses” often forms when the stratum
corneum of the epidermis increases in thickness.
○ The increased number of cell layers provides
added protection to the area that experiences
more mechanical stress. The skin over bony
prominences developed a cone-shaped structure
called a “corn”. The base of the corn is at the
surface, but the apex extends deep on the
epidermis, and the pressure on the acorn may be
painful.
○ Calluses and corns can be developed in thin and
thick skin.
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
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soles of the feet, contain less
melanin
○ To produce melanin, the enzyme tyrosinase
converts the amino acid tyrosine to
dopaquinone.
■ Dopaquinone can be converted to a
variety of related molecules, most
of which are brown to black
pigments but some of which are
yellowish or reddish
Tactile Cells
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CELLS OF THE EPIDERMIS
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Keratinocytes
○ KERATINIZATION: As keratinocytes move
from the deeper epidermal layers to the
surface, the cells change shape and
chemical composition
■ the cells eventually die and produce
an outer layer of dead, hard cells
that resists abrasion and forms a
permeability barrier
■ IMPORTANCE: determining skin
disease
which
result
from
malfunction
○ Make up the majority of epidermal cells
○ Grow and divide pushing the older cells up
toward the surface
○ Produce and fill themselves with keratin (a
hard, waterproof protein) as they move
toward the surface
○ Stratum corneum contains the keratinocytes
that have completely filled with keratin and
died
○ This process is called cornification.
Melanocytes
○ irregularly shaped cells with many long
processes that extend between the
keratinocytes of the stratum basale and the
stratum spinosum
■ Cells stay in the stratum basale
○ Produce skin pigments called melanin.
■ provides
protection
against
ultraviolet light from the sun
■ MELANIN
PRODUCTION:
determined by genetic factors
(primarily responsible for the
variations in skin color among
different races and among people of
the same race), exposure to light,
and hormones
○ NOTE that the number of melanocytes in the
skin is relatively the same for all humans,
regardless of race.
○ Keratinocytes take in melanin-filled vesicles
called melanosomes by endocytosis
○ Melanocytes may not be evenly distributed
across the skin, and denser patches of these
cells account for freckles and moles
■ Large amounts of melanin are
found in certain regions of the skin,
such as freckles, moles, the
nipples, the areolae of the breasts,
the axillae, and the genitalia
■ Other areas of the body, such as
the lips, palms of the hands, and
●
Receptors for fine touch
Found in the stratum basale associated with
nerve cells in the underlying dermis
Dendritic Cells
○ Immune system cells found in the stratum
spinosum and the stratum granulosum
○ Alert the body’s immune system to the
invasion of pathogens
Fig. Melanin concentration visual difference
Fig. Epidermis cells visual
DERMIS
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Referred to as "true skin."
Connective tissue
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
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The dermis contains:
○ Fibers
■ Collagen: main type of protein fiber
of the extracellular matrix, but
elastic and reticular fibers
○ Nerve endings (varied in structure and
function)
■ (1) free nerve endings for pain, itch,
tickle, and temperature sensations
■ (2) hair follicle receptors for light
touch
■ (3) Pacinian corpuscles for deep
pressure
■ (4)
Meissner
corpuscles
for
detecting simultaneous stimulation
at two points on the skin
■ (5) Ruffini end organs for sensing
continuous touch or pressure
○ Cutaneous glands
○ Hair follicles
○ papillae
○ Blood vessels
■ allow for nutrient and waste
exchange to the cells of the dermis
and the living cells of the epidermis
Cells of the dermis:
○ Fibroblasts
○ a few adipocytes
○ Macrophages
If the skin is overstretched, the dermis may rupture
and leave lines that are visible through the epidermis
○ These lines of scar tissue, called stretch
marks, can develop in the skin of individuals
who have experienced rapid growth
Composed of two tissue layers :
○ Superficial papillary
TWO TISSUE LAYERS
1. Dermal Papillae
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2.
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Deeper reticular layer
papillary layer derives its name from
projections that extend toward the epidermis
Cone-like projections of dermis that fit into
recesses of epidermis
Possess blood vessels, touch receptors
Loose connective tissue with thin fibers
that are somehow loosely arranged
Contain blood vessels that:
■ supply the overlying epidermis with
oxygen and nutrients
■ Remove waste products
■ aid in regulating body temperature
Under the thick skin of the palm of the hands
and sole of the feet lie in parallel curving
ridges
■ Ridges
shape
the
overlying
epidermis into pattern called
friction ridges
■ The impressions left on surfaces by
this friction form fingerprints and
footprints and this Improve grip of
hands and feet
■ Everyone has unique friction
ridge patterns, even identical twins.
Reticular Layer
○ Main layer of dermis
■ Composed of dense irregular
tissue connective tissue
○ Continuous with the subcutaneous tissue
and forms a mat of irregularly arranged
fibers that is resistant to stretching on many
directions
○ The elastic and collagen fibers are oriented
more in some directions than in others and
produce cleavage lines, or tension lines, in
the skin
■ important for health professionals to
understand cleavage line directions
because an incision made parallel
to the cleavage lines is less likely to
gap than an incision made across
them
■ The development of infections and
the formation of scar tissue are
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
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reduced in wounds where the
edges are closer together.
Intramuscular injections are used for
injecting most vaccine and certain antibiotic
Subcutaneous injection - insulin injection
SUBCUTANEOUS TISSUE
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Sometimes called as hypodermis
○ Not part of the skin
○ Deep to the skin
Attaches the skin to underlying bone and muscles and
supplies the skin with blood vessels and nerves
○ Consists of loose connective tissue with
collagen and elastic fibers
Main type of cells within the subcutaneous tissue are:
○ fibroblasts, adipocytes, and macrophages
Half of the body’s stored lipids are the subcutaneous
tissues
○ Function in insulation and padding and as a
source of energy
Can be used to estimate total body fat by pinching
the skin at selected locations and measuring the
thickness of the skin fold and underlying
subcutaneous tissue
○ The thicker the fold, the greater the amount
of total body fat
Amount of adipose tissue in the subcutaneous tissue
varies with age, sex, and diet
○ responsible for some of the differences in
body shape between individuals of the same
sex
■ Children - more adipose “chubby
baby”because
they
have
proportionately more adipose tissue
than adults
■ Adult male - less adipose than
female
■ Adult female - more adipose than
male; over thighs, buttocks & breast
Types of Injections:
○ Intradermal injection - used for the
tuberculin skin test, goes into the dermis. It
is administered by drawing the skin taut and
inserting a small needle at a shallow angle
into the skin.
○ Subcutaneous injection - extends into the
subcutaneous tissue; an insulin injection is
one example. A subcutaneous injection is
achieved by pinching the skin to form a
“tent,” into which a short needle is inserted.
○ Intramuscular injection - reaches a muscle
deep to the subcutaneous tissue. It is
accomplished by inserting a long needle at a
90-degree angle to the skin. Intramuscular
injections are used for injecting most
vaccines and certain antibiotics.
FIBERS
○
Composed of fibrous connective tissue made
by fibroblasts
■ Collagen: strength and toughness
■ Elastic fibers: extensibility and
elasticity
NUTRITION
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Nutrition is one of the many factors required
for the maintenance of overall skin health.
Am impaired nutritional status alters the
structural integrity and biological functions of
skin resulting in an abnormal skin barrier
and/or dry skin.
The importance of micro nutrients such as
certain vitamins and minerals for skin health
has been highlighted in cell culture, animal
and clinical studies. These micro nutrients
are employed not only as active compounds
in therapeutic agents for treating certain skin
diseases but also as ingredients in cosmetic
products.
There are nutritional status dependent on
both macro and micronutrients as vital for
skin health. Proper nutritional intake
compliments factors in regulating skin barrier
function.
Vitamin A and vitamin C are important for
healthy skin because they are necessary for
collagen production.
Vitamin A
■ Green and yellow vegetables, dairy
products, and liver
Vitamin C
■ Fruits and green vegetables.
■ Calcium is responsible for the
differentiation of keratinocytes as a
major cell type in epidermis.
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
NERVE ENDINGS
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Estrogen
and
production.
testosterone
increase
sebum
Pressure, pain, warm, and cold receptors
are in deeper parts of the dermis.
Lamellated and tactile corpuscles are for
pressure and touch.
Free nerve endings are for pain.
Receptor nerve endings may surround a
hair follicle.
Sweat Glands
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Also known as sudoriferous glands
Two types:
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TYPE OF SWEAT GLANDS
GLANDS
MAJOR GLANDS OF THE SKIN
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Sebaceous glands produce sebum (oil)
Sweat glands
Sebaceous Glands
● Located in the dermis
● oil-producing
● simple or compound
produce sebum
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Apocrine sweat gland
Eccrine/Merocrine sweat gland
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Eccrine/Merocrine sweat glands
○ Most common type of sweat gland
○
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○
alveolar glands that
SEBUM: oily, white substance rich in lipids
which is associated during puberty where
various hormones cause to produce lot of
sebum and this contributes to oily skin
■ If a duct of sebaceous glands is
clogged with sebum, a white heads
result. If allowed to dry and oxidize,
it will become darker forming a
black head.
■ If the sebaceous glands are
infected, it will result in a
moderate/severe form of acne.
● Excess sebum can block or
plug the ducts of the glands
forming a comedo (pimple).
The condition is called acne.
● Most common occurrence is
during puberty when sex
hormone levels rise.
Classified as Holocrine glands
○ Because sebum is released by the lysis and
death of secretory cells
Empty sebum into hair follicles
○ release their secretions into the upper part of
the hair follicles through a duct
Functions to moisturize the skin and hair
○ secretion of sebum onto the hair and
surrounding skin prevents drying and
protects against some bacteria
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Simple, coiled, tubular glands that open
directly onto the surface of the skin through
sweat pores.
distributed over the majority of the areas of
the body
■ most numerous in the palms of the
hands and soles of the feet
not found on the margin of the lips, the labia
minora, and the tips of the penis and clitoris
Secrete sweat onto skin surface directly
Clear, watery perspiration
Activated with increase in body temperature
Functions to cool the body through
evaporation
Divided into two parts:
■ Deep coil portion (located in the
dermis)
● Produces an isotonic fluid
that is mostly water but
also contains some salts
(NaCl), and small amounts
of ammonia, uric acid,
urea, and lactic acid.
■ Duct (passes to the skin surface)
● Asthis fluid moves through
the duct, sodium chloride
moves by active transport
from the duct back into the
body thereby conserving
salts.
● so the resulting hypo
osmotic fluid that leaves
the duct is called sweat.
So
when
the
body
temperature starts to rise
above normal the sweat
glands produce sweat
Page 8 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
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which evaporates and
cools
the
body.
(thermoregulation)
sweat
can
also
be
released in the palms
soles and axillary as a
result of emotional stress.
Apocrine sweat gland
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Simple, coiled, tubular glands that open into
the hair follicle superficial to the opening of
the sebaceous glands.
Typically larger and more productive than
eccrine glands
Characterized by a simple cuboidal
epithelium
Secretion
contains
protein,
lipid,
carbohydrates, ammonium, and other
organic compounds.
■ Contains 3 Methyl-2 hexanoic acid
● essentially odorless body
odor due to bacterial
decomposition when first
released but are quickly
metabolized by bacteria to
cause body odor.
●
Many mammals use scent
as
a
means
of
communication
Becomes active in puberty as a result of sex
hormones
■ Physiology says that the activity of
apocrine sweat glands may signal
sex maturity.
Empty secretion into hair follicle
Located in axillary and genital regions
(scrotum,labia majora, and around the anus)
Milky sweat due to proteins and fats
●
Mammary gland
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Modified apocrine sweat glands located in
the breast (In breast tissue)
normally only functional in lactating women
■ Produces milk (in female);
■ Nourishes an infant
non functional form (in males)
Regulated in the endocrine system and
becomes functional in response to the
hormonal changes associated in giving birth.
OTHER GLANDS
●
HAIR
Ceruminous gland
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Produce cerumen or earwax
Found in external auditory canal
■ Keep foreign particles and insects
out of auditory canal
Modified eccrine sweat glands located in the
ear canal.
■ Ear wax is composed of the
combined secretions of ceruminous
glands and sebaceous glands.
■ Cerumen and hair in the ear canal
protect the tympanic membrane
by preventing dirt and small insects
from moving too deeply into the ear
canal
● However, an accumulation
of cerumen can block the
ear canal and make
hearing more difficult.
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presence of hair is one of the characteristics of all
mammals
○ if the hair is dense and covers most of the
body surface, it is called fur
○ In humans, hair is found everywhere on the
skin except the palms, the soles, the lips, the
nipples, parts of the external genitalia, and
the distal segments of the fingers and toes.
The three types of hair are lanugo, vellus, and
terminal.
A hair can be divided into three sections: the bulb, the
root, and the shaft.
HAIR STRUCTURE
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●
change as a person ages
There are three layers to a hair :
○ the inner medulla - central acces of the hair.
Consist of two or three layers of cells
containing soft keratin
○ the cortex - cells constrain hard keratin.,
Surrounds medula. Contains the bulk of the
hair. Covered by the cuticle
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UNIT II: THE INTEGUMENTARY SYSTEM - LAB
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the cuticle- single layer of cells that
constrain hard keratin. The Edges are
overlapping.
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Keratinocytes: produce the hair and form
the hair matrix
Melanocytes: provide pigment for the hair
HAIR FOLLICLE
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tube-like invaganiation of the epidermins that extends
to the dermis
Hair develops and grows with each hair follicle
Consists of dermal root shift and epithelial root
shifts
○ Dermal root shift is the portion of the
dermis that surrounds the epithelial root shift.
○ The Epithelial root shift is divided into
external and internal parts.
■ EXTERNAL: At the opening of the
follicle, the external epithelial root
shift, has all the starta found in the
thin skin.The deeper in the hair
follicle, the number of cells
decreases until the hair bulb, only
stratum basale is present. This
arrangement of epidermal cells has
important consequences for skin
repair. So if the epidermis and
superficial
part
dermis
are
damaged, the keratinocyte stem
cells in the stratum basale of the
undamaged part of the hair follicle
can be the source of the hair
epithelium
■ INTERNAL: has raised edges that
mesh closely with the raised edges
of the hair cuticle and this
arrangement holds the hair in place.
When a hair is pulled out, the
internal epithelial root sheath
usually comes out as well and is
plainly visible as whitish tissue
around the root of the hair.
Contains the hair root
Formed by the stratum basale
Arrector pili muscle
○ Associated with each hair follicle are these
smooth muscle cells
■ extend from the dermal root
sheath of the hair follicle to the
papillary layer of the dermis
○ The hair follicle and the hair inside it are at
an oblique angle to the surface of the skin
○ Contracts and raises the hair in the follicle on
end
■ PROCESS: When the arrector pili
muscles contract, however, they
pull the follicle into a more
perpendicular position, causing the
hair to “stand on end.”
■ Movement of the hair follicles
produces raised areas which
causes “goose bumps”
● common response to cold
temperatures as well as strong
emotional responses
○ Little value for human survival
■ But in other mammals, arrector pili
muscle contractions are important
for
warmth
as
well
as
communication of aggression or
fear
The dermal papilla has a blood vessel, which feeds
hair follicle cells:
Fig. Hair Follicle
Page 10 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
THREE TYPES OF HAIR
●
Lanugo Hair
○
○
●
○
○
○
○
Vellus hair is the body hair on most women
and children
Prepubertal stage
At puberty, terminal hair esp in pubic and
axillary region replaces much of the vellus
hair
Terminal Hair
○ Thick, coarse, and heavily pigmented,
○
○
○
●
○
Vellus Hair
○ Unpigmented and very fine
○ replaces lanugo hair around the time of birth
○
●
○
Very fine, delicate and unpigmented
(colorless)
type of hair seen in developing fetus
■ Forms on a fetus during the last
three months of its development
(By the fifth or sixth month of fetal
development)
Lanugo hair is usually replaced by birth
forms the eyebrows, eyelashes, and hair on
the scalp.
Adult stage
At puberty, terminal hair forms in the axillary
and pubic regions of both sexes. It also
forms on the face and possibly on the trunk
and limbs of men.
■ These changes in hair type at
puberty are universal and have
biological significance
■ The beard, pubic, and axillary hair
are visible signs of sexual maturity
● Pubic and axillary hair may
function
as
wicks
for
dispersing odors produced
by secretions from specialized
glands in the pubic and
axillary regions acting as
olfactory signals to others. It
also has been suggested that
pubic hair protects against
abrasion during intercourse
and axillary hair reduces
friction when the arms move
against the body.
Chest, leg and arm hair is approximately
90% terminal hair in male and 35% in female
■ In males, terminal hairs replace the
vellus hairs of the face to form the
beard
All types of human hair can be divided into
three sections (shown in Figure 3.9):
○
(1) The bulb is a thickening of the hair at the
end of the hair follicle.
■ Base of the root is expanded to
form hair bulb; an expanded knob
at the base of the hair root
■ Inside the hair bulb is a mass of
undifferentiated
epithelial
cells
called the matrix.
● MATRIX: produces both the
hair and the internal epithelial
root sheath
● The dermis of the skin projects
into the hair bulb as a hair
papilla. Within the hair papilla
are blood vessels that provide
nourishment to the cells of the
matrix.
(2) The root extends from the bulb to the
skin’s surface; located below the surface
(3) The shaft is the section of the hair
extending out from the skin’s surface. It
protrudes above the surface of the skin.
most of the root and the shaft are composed
of column of dead keratinized epithelial
layers arranged in three concentric layers:
■ (1) the medulla: central axis of the
hair, and it consists of two or three
layers of cells containing soft
keratin
■ (2) the cortex: surrounds the
medulla and forms the bulk of the
hair. The cells of the cortex contain
hard keratin
■ (3) the cuticle: covers the cortex, a
single layer of cells also containing
hard keratin. The edges of the
cuticle cells overlap like shingles on
a roof.
HAIR COLOR AND TEXTURE
●
●
●
Hair color is the result of the melanin production by
the melanocytes and the distribution of melanin to
the cells of the hair
○ Similar to how melanocytes of the epidermis
produce melanin and pass it to the
keratinocytes of the skin.
○ Melanocytes within the hair bulb matrix
produce melanin and pass it to the
keratinocytes in the hair cortex and medulla.
The skin having varying amounts and types of
melanin cost different shades of hair color.
○ The blonde hair has a little black brown
melanin.
○ Jet black hair has the most intermediate
amount of melanin accounting for the
different shades of brown.
○ Red hair is caused by varying amounts of
the red type of melanin.
○ Hair sometimes contains both black brown
or red melanin.
Hair color is controlled by several genes and dark
hair color is not necessarily dominant over light.
Page 11 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
●
●
■
With age the amount of melanin in hair can decrease
causing hair color to fade or become white.
○ Gray hair is usually a mixture of faded and
unfaded and white hair.
The development of high resolution Digital
microscopes allow researchers to obtain more
accurate measurements of hair features. There are
studies that have been done using a digital
microscopy and to explore variants within the cortical
texture color and density characteristics throughout
hair strands.
○ Changes in your hair's thickness, texture and
growth location (too little in some places, too
much in others) can also occur.
●
●
Regrowth of hair occurs in many
individuals, but some experience
permanent hair loss.
● the most common kind of
permanent hair loss is “pattern
baldness” wherein hair follicles
shrink and revert to producing
vellus hair, which is very short,
transparent, and for practical
purposes invisible. . Eventually,
hair production in these smaller
follicles may completely cease
● Baldness is more common
and more pronounced in
certain men, it can also occur
in women. Genetic factors
and
the
hormone
testosterone are involved in
causing pattern baldness.
The length of each stage depends on the hair:
○ EYELASHES: grow for approximately 30
days and rest for 105 days
○ SCALP HAIR: grow for 3 years and rest for
1–2 years
Maximum hair length is determined by the rate of hair
growth and the length of the growing phase
○ scalp hair can become very long
○ eyelashes stay short
HAIR GROWTH CYCLE
●
HAIR GROWTH
●
●
Hair goes through a growing stage and a resting
stage, and then it falls out.
Not all of the hairs on the head cycle are on the
same schedule.
○ Each hair grows about a half inch per
month, and its growth stage lasts for
approximately three years
○ average
rate
of
hair growth is
approximately 0.3 mm per day
■ Cutting, shaving, or plucking hair
does not alter the growth rate or
the character of the hair
● But hair can feel coarse and
bristly shortly after shaving
because the short hairs are less
flexible
○ Roughly 90 percent of the hairs on your
head are somewhere in the growing stage
at any given time
○ Normally lose about 100 hairs from your
scalp every day
■ Hair loss can be more extensive
than the normal 100 hairs per day.
■ ALOPECIA AREATA: often called
spot baldness, involves varying
degrees of hair loss and can affect
all areas of the body.
● most
likely
due to an
autoimmune response, where
the defense cells of the body
destroy normal, healthy cells.
●
PROCESS:
○ During the growth stage, a hair increases in
length as new matrix cells are produced,
differentiate, become keratinized, and die.
○ The hair grows longer as cells are added
at the base of the hair root.
○ Eventually, hair growth stops; the hair
follicle shortens and holds the hair in
place.
○ A resting period follows. Each hair then
goes into a one to two year resting stage,
and then it falls out
○ After which a new cycle begins.
○ With this new cycle, a new hair forms to
replace the old hair, which falls out of the
hair follicle. Thus, losing a hair normally
means that the hair is being replaced.
PHASES:
1. Anagen (Growth phase)
● Nourishment of hair follicle via
blood supply enables hair growth
2. Catagen (Transition phase)
● Hair follicle detaches from the
nourishing blood supply.
3. Telogen (Resting phase)
● Without nourishment, the hair dies
and falls out.
NAILS
●
●
●
●
Thin plate consisting of layers of dead stratum
corneum cells that contain a very hard type of
keratin.
Located at the distal ends of the digits (fingers and
toes).
protect the ends of the fingers and toes, aid in
grasping small objects, and are used for scratching.
Consist of proximal nail root and distal nail body.
○ Nail Root - covered by skin
Page 12 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
○
○
○
○
○
○
○
○
○
○
○
●
Nail Body - visible portion of the nail. It lies
on the nail bed
Nail Fold - covers the Lateral and Proximal
edges of the nail.
Nail Groove - hold the edges of the nail in
place
Cuticle/Eponychium - stratum corneum of
the nail fold which grows into the nail body.
Hyponychium - skin under the free edge of
the nail. Thicken region of the stratum
corneum.
Nail root extends distally from the nail
matrix which is growth center at the root of
the nail is composed of active keratinocytes
in the stratum basale
The nail also attaches into the underlying
nail bed, which is located between the nail
matrix and the hyponychium.
■ The nail matrix and the bed is
composed of the epithelial tissue,
with a stratum basale that gives
rise to the cells that form the nail,
both contributing to the growth of
the nail
■ The nail matrix is thicker than the
nail bed and produces nearly all of
the nail.
■ The nail bed is visible through the
clear nail and appears pink
because of the blood vessels in the
underlying dermis
A small part of the nail matrix (lunula), is
seen through the nail body as a whitish
crescent shaped area at the base of the
nail.
■ The lunula, seen best on the thumb,
appears white because the blood
vessels do not show through the
thicker nail matrix.
The free edge of the nail and the nail body
make up the nail plate.
As the nail forms in the nail matrix and bed, it
slides over the nail bed towards the distal
end of the digit.
The nails grow at an average rate of 0.5 to
1.2 mm per day.
■ fingernails grow more rapidly than
toenails.
■ Unlike hair, they grow continuously
throughout life and do not have a
resting phase
PHYSIOLOGY OF THE INTEGUMENTARY SYSTEM
FUNCTIONS OF THE SKIN
The functions of the integumentary system include:
1.
2.
3.
4.
5.
6.
7.
Protection from pathogens and UV light
Vitamin D production
Temperature regulation
Water retention
Sensation
Nonverbal communication
Excretion
Protection from pathogens and UV light
●
●
●
●
●
●
●
Anatomy of a nail
●
●
●
Integumentary system is the body’s outer barrier
which defends it from harm. Hence, it is the body’s
first line of defense.
Difficult for pathogens to penetrate
Dry, acidic surface is unfriendly to bacteria
Melanin absorbs and protects underlying cells from
UV light damage.
The skin protects underlying structures from
mechanical damage. Both the dermis and the
epidermis play roles in this line of defense, but in
different ways.
○ The dermis, particularly the irregular dense
connective tissue of the reticular layer,
provides structural strength, preventing
tearing of the skin.
○ The stratified epithelium of the epidermis
protects against abrasion. As the outer cells
of the stratum corneum slough off, they are
replaced by cells from the stratum basale.
Calluses develop in areas subject to heavy
friction or pressure.
The skin prevents microorganisms and other foreign
substances from entering the body.
○ Secretions from skin glands produce an
environment
unsuitable
for
some
microorganisms.
○ The skin also contains components of the
immune
system
that
act
against
microorganisms
Hair provides protection in several ways.
○ The hair on the head acts as a heat insulator
and protects against ultraviolet light and
abrasion.
○ The eyebrows keep sweat out of the eyes,
○ Eyelashes protect the eyes from foreign
objects
○ Hair in the nose and ears prevents dust and
other materials from entering.
○ Axillary and pubic hair protect against
abrasion.
Nails protect the ends of the fingers and toes from
damage and can be used in defense.
The intact skin plays an important role in reducing
water loss because its lipids act as a barrier to the
diffusion of water.
Some lipid-soluble substances readily pass through
the epidermis.
○ Lipid-soluble
medications
can
be
administered by applying them to the skin,
after which the medication slowly diffuses
through the skin into the blood.
○
For example, nicotine patches are applied
to help reduce withdrawal symptoms in
people attempting to quit smoking.
Page 13 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
Vitamin D production
●
●
●
●
Important for the regulation of calcium and phosphate
homeostasis
PRIMARY ROLE: stimulate the uptake of calcium and
phosphate from the small intestine
○ Adequate levels of these minerals are
necessary for normal bone metabolism
and calcium is required for normal nerve
and muscle function.
Vitamin D synthesis begins in skin when it is exposed
to ultraviolet light. UV light encourages skin to
produce vitamin D.
○ People can produce all the vitamin D they
require by this process if enough ultraviolet
light is available.
■ However, because people live
indoors and wear clothing, their
exposure to ultraviolet light may not
be adequate for the manufacture of
sufficient vitamin D. This is
especially likely for people living in
cold climates because they remain
indoors or are covered by warm
clothing when outdoors.
■ Fortunately, vitamin D can also be
ingested and absorbed in the
small intestine. Natural sources of
vitamin D are liver (especially fish
liver), egg yolks, and dairy products
(e.g., butter, cheese, and milk). In
addition,
the
diet
can
be
supplemented with vitamin D in
fortified milk or vitamin pills
Vitamin D synthesis involves a precursor molecule,
7-dehydrocholesterol, which is stored in the skin.
○ When exposed to ultraviolet light, the
precursor molecule is converted into
cholecalciferol.
○ Cholecalciferol is released into the blood
and modified first by the liver and later by the
kidneys to form active vitamin D3, also
called calcitriol.
■ Calcitriol is an important hormone,
a chemical messenger that travels
through the blood, regulating
calcium homeostasis.
○
○
Water Retention
●
The skin’s epidermis waterproofs the body by keeping
water from the environment out and body fluids in.
Sensation
●
●
●
●
●
Nerve endings are located in the stratum basale, and
dermis respond to stimuli
Receptors in the skin can detect:
○ Temperature (heat & cold)
○ Pain
○ Touch
○ Pressure
The epidermis and dermal papillae are well supplied
with touch receptors
The dermis and deeper tissues contain pain, heat,
cold, touch, and pressure receptors
Hair follicles (but not the hair) are well innervated, and
sensory receptors surrounding the base of hair
follicles can detect hair movement
Nonverbal communication
●
●
●
Blushing when embarrassed
Pale when frightened
Color, texture, silkiness, and other qualities of the skin
and hair can all be indicative of overall health
Additional function: Excretion
●
Excretion is the removal of waste products from the
body.
○
Temperature Regulation
●
●
●
Body temperature is affected by blood flow through
the skin
When blood vessels (arterioles) in the dermis dilate,
more warm blood flows from deeper structures to the
skin, and heat loss increases. In other words, it dilate
to increase blood flow to the skin so that heat can
radiate out of the body.
○ Body temperature tends to increase as a
result of exercise, fever, or a rise in
environmental temperature.
○ In order to maintain homeostasis, this
excess heat must be lost.
■ The body accomplishes this by
producing sweat.
● The sweat spreads over the
surface of the skin; as it
evaporates, the body loses
heat.
Blood vessels in the dermis constrict, less warm
blood flows from deeper structures to the skin, and
heat loss decreases. In other words, it constricts to
preserve heat for the body’s core.
If body temperature begins to drop below
normal, heat can be conserved by a
decrease in the diameter of dermal blood
vessels.
Contraction of the arrector pili muscles
causes hair to stand on end, but this does
not significantly reduce heat loss in
humans because so little hair covers the
body.
■ However, the hair on the head is
an effective insulator.
In addition to water and salts, sweat
contains a small amount of waste products,
including urea, uric acid, and ammonia.
However, even when large amounts of sweat
are lost, the quantity of waste products
eliminated in the sweat is insignificant
because the urinary system excretes most
of the body’s waste products.
INJURIES TO THE SKIN
●
Regeneration versus fibrosis
○
○
○
Skin can heal by regeneration or fibrosis.
In regeneration, normal function returns.
■ •The stratum basale cells reach
contact
inhibition
before
the
fibroblasts fill the area with scar
tissue.
In fibrosis, normal functioning tissue is
replaced by scar tissue.
■ Fibroblasts’ collagen fibers produce
granulation tissue to fill in the
wound’s clot.
■ Fibroblasts reach contact inhibition
before the cells of the stratum
basale cells.
Page 14 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
■
■
●
Burns
○
○
○
○
It is an injury to a tissue caused by heat,
cold, friction, chemicals, electricity, or
radiation
Burns can be classified by degree.
(considering the (1) extent of surface area
involved and the (2) depth of the burn)
■ In adults, the rule of nines is used
to determine the extent of a burn.
● which divides the body into
areas that are approximately
9%, or multiples of 9%, of the
body surface area
■ For younger patients, surface area
relationships are different.
● For example, in an infant, the
head and neck are 21% of
BSA, whereas in an adult they
are 9%.
● For burn victims younger than
age 15, a table specifically
developed for them should be
consulted.
On the basis of depth, burns are classified
as either partial thickness or full-thickness
burns.
■ Partial thickness are subdivided into
first and second degree burns
■ Full
thickness
are
called
third-degree burns.
Degrees:
■ First-degree burns involve only the
epidermis. It may result in redness,
pain, and swelling. They can be
caused by sunburn or brief
exposure to hot or cold objects,
■
and they heal in a week or so
without scarring.
Second-degree burns involve the
epidermis and dermis. Symptoms
include redness, pain, edema,
swelling, and blisters. Healing takes
approximately 2 weeks, and no
scarring results.
● However, if the burn goes deep
into the dermis, the wound
appears red, tan, or white; may
take several months to heal;
and might scar.
● In all second-degree burns, the
epidermis regenerates from
epithelial tissue in hair follicles
and sweat glands, as well as
from the edges of the wound
Third-degree burns involve the
epidermis,
dermis,
and
hypodermis. The epidermis and
dermis are completely destroyed,
and tissue just below the skin may
be involved. Third-degree burns
are often surrounded by first- and
second-degree burns.
● Although the areas that have
first- and second-degree burns
are painful, the region of
third-degree burn is usually
painless because the sensory
receptors
have
been
destroyed.
● Third-degree burns appear
white, tan, brown, black, or
deep cherry-red. Skin can
regenerate only from the
edges, and skin grafts are
often necessary.
● Symptoms include charring
and no pain at the burn site
Fourth-degree
burns
are
extremely severe burns that affect
tissues
deeper
than
the
subcutaneous
tissue,
often
damaging tendons, fascia, muscle,
and bone.
● Like
third-degree
burns,
fourth-degree
burns
are
painless
due
to
the
destruction
of
sensory
receptors.
● Because of the severity of
tissue damage, fourth-degree
burns
often
require
amputation or removal of
damaged tissue. Death may
occur due to the increased
likelihood of infection.
Page 15 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
/GRAPHIC CONTENT WARNING! Some images may be
disturbing to some individuals./
●
●
●
DIAGNOSTIC TESTS USED TO DIAGNOSE
INTEGUMENTARY SYSTEM DISORDERS
●
Three diagnostic tests are commonly used:
○ Skin biopsy: the removal of a piece of
tissue or a sample of cells from a body so
that it can be analyzed in a laboratory
○ Skin scraping: the taking of skin cell
scrapings so that the cells can be viewed
under a microscope
○ Wood’s light: the use of a black light to view
pigment changes in the skin
●
the subcutaneous tissue cause the skin to
sag and wrinkle.
Retin-A is a vitamin A derivative that appears to be
effective in treating fine wrinkles on the face, such as
those caused by long-term exposure to the sun; it is
not effective in treating deep lines.
○
One ironic side effect of Retin-A use is
increased sensitivity to the sun’s ultraviolet
rays. Doctors prescribing this cream caution
their patients to always use a sunblock when
they are going to be outdoors.
The skin also becomes drier with age as sebaceous
gland activity decreases.
○
Decreases in the activity of sweat glands
and the blood supply to the dermis result in a
reduced ability to regulate body temperature.
■ Elderly individuals who do not take
proper precautions may experience
heat exhaustion, which can even
lead to death.
The number of functioning melanocytes generally
decreases; however, in some localized areas,
especially on the hands and face, melanocytes
increase in number, producing age spots. (Age spots
are different from freckles, which are caused by an
increase in melanin production, not an increase in
melanocyte numbers.) White or gray hairs also
appear because of a decrease in or lack of melanin
production.
Skin that is exposed to sunlight appears to age more
rapidly than non exposed skin.
○ This effect is observed on areas of the body
that receive sun exposure, such as the face
and hands.
○ However, the effects of chronic sun exposure
on the skin are different from the effects of
normal aging. In skin exposed to sunlight,
normal elastic fibers are replaced by an
interwoven mat of thick, elastic-like material,
the number of collagen fibers decreases,
and the ability of keratinocytes to divide is
impaired.
DISORDERS
●
Skin cancer
○
○
Skin cancer is the most common cancer, and
it is associated with sun exposure.
Basal cell carcinoma is the most common
skin cancer, and it tends not to metastasize.
INTEGUMENTARY SYSTEM DISORDERS
●
●
As the body ages, the skin is more easily damaged
because the epidermis thins and the amount of
collagen in the dermis decreases.
Skin infections are more likely, and skin repair occurs
more slowly.
○
A decrease in the number of elastic fibers in
the dermis and a loss of adipose tissue from
○
Squamous cell carcinoma results from
keratinocytes in the stratum spinosum. They
commonly form on the face, hands, ears,
and neck and can metastasize.
Page 16 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
○
○
○
Malignant melanoma is the rarest form of
skin cancer. It is the most deadly because it
metastasizes easily. Usually begins in a
mole.
●
Skin infections
●
Bacterial skin infections
○
○
○
●
Fungal skin infections
●
Parasitic skin infections
○
Tinea Infections
■ Contact with an infected person,
damp surfaces
■ Includes ringworm, athlete’s foot,
and jock itch.
■ a circular rash that clears from the
center,
giving
it
a
ringlike
appearance
Skin can be infected by a type of bacteria, a
virus, fungus, or parasite.
Impetigo: caused by the bacterium
Staphylococcus or Streptococcus. Appears
as a cluster of vesicles that burst and crust
over, which may cause pain and itching.
Cellulitis: infection of the skin’s dermis or
hypodermis and is frequently caused by
Streptococcus or Staphylococcus bacteria.
Commonly occurs on the face and lower
legs, characterized by redness and swelling
of an area of the skin that increases in size
rapidly.
○
●
Herpes Simplex Virus (HSV): small, painful
blisters that appear on the skin and on the
mucous membranes of the mouth (HSV-1) or
genitals (HSV-2). Contagious.
Herpes
Varicella
Zoster:
causes
chickenpox in children and shingles in
adults.
Scabies
■ Caused by an infestation of mites
■ Causes small red bumps on the
skin that itch severely
Viral skin infections
○
Warts: growth caused by HPV.
Page 17 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
●
Other common skin disorders
○
Psoriasis
■ Characterized by an overgrowth of
skin
cells
and
improper
keratinization of the epidermis and
nails
■ It is an autoimmune disorder that
runs in families
○
Scleroderma
■ It involves the accumulation of
■
■
○
excess connective tissue in the skin
and various organs.
The excess collagen causes
hardening of the skin and organs,
with decreased elasticity; this leads
to a decrease in function.
It can be caused by exposure to
certain chemicals or can be
associated
with
autoimmune
diseases such as lupus.
Atopic Dermatitis (Atopic Eczema)
■ It is an allergic reaction that causes
an infection
ADDITIONAL
REPRESENTATIVE
DISEASES
AND
DISORDERS OF THE INTEGUMENTARY SYSTEM (FROM
BOOK TABLE 5.2)
■
○
It can cause the skin to have a
leathery appearance and be
discolored
Hives (Urticaria)
■ It is a skin reaction that can be
caused by insect bites or by contact
with substances that can cause an
allergic reaction, such as certain
foods or drugs.
■ The symptoms include raised areas
of the skin, redness, and itching.
CONDITION
DESCRIPTION
Birthmarks
Congenital (present at birth) disorders of
the dermal capillaries
Ringworm
Fungal infection that produces patchy
scaling and inflammatory response in the
skin
Eczema and
dermatitis
Inflammatory conditions of the skin
caused by allergy, infection, poor
circulation, or exposure to chemical or
environmental factors
Frostbite
-
Psoriasis
Chronic skin disease characterized by
thicker-than-normal epidermal layer
(stratum corneum) that sloughs to
produce large, silvery scales; bleeding
may occur if the scales are scraped
away
Vitiligo
Development of patches of white skin
where melanocytes are destroyed,
apparently by an autoimmune response
Alopecia areata
-
Skin cancer
Page 18 of 19
UNIT II: THE INTEGUMENTARY SYSTEM - LAB
BACTERIAL INFECTIONS
Impetigo
Small blisters containing pus; easily
rupture to form a thick, yellowish crust;
usually affects children
Erysipelas
Swollen patches in the skin caused by
the bacterium Streptococcus pyogenes
Decubitus
ulcers
(bedsores,
pressure
sores)
Develop in people who are bedridden or
confined to a wheelchair; compression of
tissue and reduced circulation result in
destruction of the skin and
subcutaneous tissue, which later
become infected by bacteria, forming
ulcers
Acne
Develops when sebum — an oily
substance that lubricates your hair and
skin — and dead skin cells plug hair
follicles. Bacteria can trigger
inflammation and infection resulting in
more severe acne
Fig. ingrown
VIRAL INFECTIONS
Rubeola
(measles)
Skin lesions; caused by a virus
contracted through the respiratory tract;
may develop into pneumonia or infect the
brain, causing damage
Rubella
(German
measles)
Skin lesions; usually mild viral disease
contracted through the respiratory tract;
may be dangerous if contracted during
pregnancy because the virus can cross
the placenta and damage the fetus
Chickenpox
Skin lesions; usually mild viral disease
contracted through the respiratory tract
Shingles
Painful skin lesions; caused by the
chickenpox virus after childhood
infection; can recur when the dormant
virus is activated by trauma, stress, or
another illness
Cold sores
(fever blisters)
Skin lesions; caused by herpes simplex I
virus; transmitted by oral or respiratory
routes; lesions recur
Genital herpes
Genital lesions; caused by herpes
simplex II virus; transmitted by sexual
contact
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