The Integumentary system
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two major components
1. cutaneous membrane
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A. epidermis /superficial epithelium
B. dermis/underlying connective tissues.
C. hypodermis/ Deep to the dermis
2. accessory structures
hair, nails, exocrine glands, blood vessels,
sensory receptors for touch, pressure,
temperature, and pain
functions of the skin
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Protection - organs against shocks, abrasion, and
chemical attack.(stratified squamous epithelium)
Excretion - salts, water, and organic wastes by
glands.
Maintenance of temperature - insulation or
evaporation
Synthesis of vitamin D3 - steroid converted to
hormone calcitriol, important to normal calcium
metabolism and membrane repair.
Storage - nutrients.lipids
Detection - touch, pressure, pain, and temperature
The Epidermis
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are four cell types found in the
epidermis
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Keratinocytes
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Produces a tough protein called keratin
Melanocytes
Pigment cells located deep in the epidermis
 Produce melanin (skin color)
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Merkel cells
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Sensory cells
Langerhans cells
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Fixed macrophages
The Epidermis
 Thick
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and thin skin
Thick skin
Found on palms and soles
 Made of five layers of cells
 Has stratum lucidum
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Thin skin
Found on the rest of the body
 Made of four layers of cells
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LAYERS OF THE EPIDERMIS
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In order, from the basal lamina toward the free
surface, are the
stratum germinativum(basale),
stratum spinosum,
stratum granulosum,
stratum lucidum,
stratum corneum.
Stratum
granulosum
Stratum
spinosum
stratum germinativum/basale
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Dermal projections called dermal papillae extend
between adjacent epidermal ridges
The contours of the skin surface follow the ridge
patterns - Fingerprints
Large basal cells, or germinative stem cells, dominate
the stratum germinativum.
Skin surfaces that lack hair also contain Merkel cells
that are sensitive to touch; when compressed, they
release chemicals that stimulate sensory nerve
endings.
The brown tones of skin result from the pigment cells
called melanacytes, with cell processes extending into
more superficial layers.
Stratum
granulosum
Stratum
spinosum
Stratum Spinosum
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Each time a stem cell divides, one of the
daughter cells is pushed from the stratum
germinativum into the stratum spinosum,
The stratum spinosum consists of 8 to 10 layers
of cells
Langerhans cells (fixed macrophages) present,
stimulate a defense against (1) microorganisms
that manage to penetrate the superficial layers
of the epidermis and (2) superficial skin
cancers.
Stratum
granulosum
Stratum
spinosum
Stratum Granulosum
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consists of three to five layers of keratinocytes
displaced from the stratum spinosum.
By the time cells reach this layer, most have stopped
dividing & they begin making large amounts of
keratin and keratohyalin
Keratin is a tough fibrous protein component of hair
and nails.
Keratohyalin forms dense granules that dehydrate the
cell and aggregate cross-linking of the keratin fibers.
The nuclei and other organelles disintegrate, and the
cells die.
dehydration creates a tightly interlocked layer of cells
of keratin fibers surrounded by keratohyalin.
Stratum
granulosum
Stratum
spinosum
Stratum Lucidum
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In the thick skin of the palms and soles, a
glassy stratum lucidum covers the
stratum granulosum
The cells in the stratum lucidum are
flattened, densely packed, and filled with
keratin.
thick skin, on the palms and soles have
five layers … lucidum is the 5th layer
Stratum
granulosum
Stratum
spinosum
Stratum Corneum
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At the exposed surface of both thick skin and thin skin
contains 15 to 30 layers of keratinized cells.
remain tightly interconnected by desmosomes. shed in
large groups or sheets rather than individually.
15 to 30 days for a cell to move from the stratum
germinativum to the stratum corneum.
The dead cells remain in the exposed stratum
corneum layer for an additional two weeks before they
are shed
insensible perspiration Water from interstitial
fluids slowly evaporates into the surrounding air. You
lose roughly 500 ml (about 1 pt) of water in this way
each day.
Skin Color
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Three pigments contribute
(1) melanin - amount and kind (yellow, reddish brown, or black)
(2) carotene - orange-yellow found in carrots & orange, deep yellow, or
leafy green vegetables.
(3) oxygen – amount bound to hemoglobin
people who produce a lot of melanin have brown-toned skin.
the crimson color of oxygen-rich hemoglobin gives the skin a rosy color
When hemoglobin is poorly oxygenated, the skin appear blue, a condition
called cyanosis
Cyanosis is common during heart failure and severe breathing disorders.
skin color signals disease states:
• Rubor, Redness, or erythema - embarrassment (blushing), fever,
hypertension, inflammation, or allergy.
• Pallor, or blanching - emotional stress (fear, anger, and others), Pale
skin may also signify
anemia, low blood pressure, or impaired blood flow into the area.
• Jaundice, or a yellow- cast – liver disorder excess bile pigments in the
blood
Bruises - sites where blood has escaped and has clotted in the tissue
spaces.(hematomas) unusual bruising may signify a deficiency of vitamin C
or hemophilia
melanin
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produced by melanocytes
sunlight stimulates the melanocytes to produce more melanin
(tanning)
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Freckles and moles are where melanin is concentrated in one
spot.
excessive sun eventually damages the skin.
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basale cells phagocytize the melanin & form a protective "umbrella" over
nuclei (DNA) from ultraviolet radiation in sunlight.
It causes the elastic fibers to clump, leading to leathery skin. It also
depresses the immune system.
Overexposure to the sun can also alter the DNA of skin cells
and in this way lead to skin cancer.
Dermis
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The dermis is your "hide." It is leather
The dense fibrous connective tissue has two major
regions— papillary and reticular
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The papillary layer is the upper region. It is
uneven and has fingerlike projections called
dermal papillae that create fingerprints
They contain capillaries, pain receptors (free
nerve endings) and touch receptors called
Meissner's corpuscles
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The reticular layer is the deepest skin layer.
It contains blood vessels, sweat and oil glands,
and deep pressure receptors called Pacinian
corpuscles & phagocytes That attack bacteria
As we age we produce less collagen and elastin
and fat decreases (wrinkles)
hypodermis
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Foundation that attaches to bone and muscle
Supplies skin with blood vessels and nerves
Consists of loose connective tissue
Called subcutaneous tissue or superficial fascia
½ of the body’s fat is in hypodermis
Insulates, energy, padding
Used to calculate total body fat
The Dermis
 Wrinkles
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Under normal circumstances, the fibers of the
reticular layer of the skin stretch and recoil.
Skin wrinkles are due to:
Age
 UV light
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The Dermis
 Stretch
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Marks
Extensive stretching during pregnancy causes
reticular fibers to break
The skin does not recoil
The skin wrinkles and creases resulting in
stretch marks
The Dermis
 Lines
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of Cleavage
Fibers have a tendency to organize
themselves in a parallel fashion
In certain areas of the body, there
is a pattern
To reduce scar formation
(extensive damage to the fibers),
surgeons try to cut parallel to the
lines of cleavage
Accessory
Glands in the
skin
Structures
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1. Sebaceous glands
2. Sweat glands
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Apocrine glands
Ceruminous glands (a type of apocrine gland)
Mammary glands (a type of apocrine gland)
Merocrine glands
Both formed by stratum basale & push into dermis.
 Gland
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function:
Lubricates the epidermis, excretes waste,
assists in thermoregulation
Cutaneous
Exocrine
Glands (all are exocrine glands)
Glands - release secretions to surface via ducts
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1. Sebaceous (Oil)
Glands –
- all over except on the
palms of hands and feet.
Their ducts usually
empty into a hair follicle
but
some open directly onto
the skin surface.(lips,
eyelids, genitalia)
sebum (seb = grease),
mixture of oily
substances and
fragmented cells
lubricate skin & kill
bacteria,
male sex hormones
produced in both sexes
during adolescence
increase sebum
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2. Sweat Glands (sudoriferous= sweat)—
more than 2.5 million per person.
There are two types merocrine/eccrine and apocrine.
Merocrine/eccrine glands - more numerous all over the
body. produce sweat, primarily water plus salts, vitamin C,
traces of metabolic wastes (ammonia, urea, uric acid), and
lactic acid (attracts mosquitoes).
Sweat is acidic (pH from 4 to 6), and inhibits growth of
bacteria, which are always present on the skin surface.
Apocrine glands - confined to axillary and genital areas
their ducts empty onto hair follicles.
Their secretion contains fatty acids, proteins, salt & water
may have a milky or yellowish color. odorless, but when bacteria that live
on skin use its proteins and fats it has an unpleasant odor.
Apocrine glands begin to function during puberty under the
influence of androgens.
Their precise function is not yet known, but they are activated by nerve
fibers during pain and stress and during foreplay.
Accessory Structures
 Sweat
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glands
Mammary glands
A special type of apocrine gland
 Produce milk under the control of hormones from
the pituitary gland
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Ceruminous glands
A special type of apocrine gland
 Found only in the ear canal
 Produce cerumen (ear wax)
 Provide minimal protection associated with the ear
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Disorders
Sebaceous (Oil) Glands
Acne
 Active infection of sebaceous
glands
 Can be mild or extremely
severe
Whitehead
 A sebaceous gland‘s duct
becomes blocked by sebum
Blackhead
 Accumulated material oxidized,
dries, and darkens
Hairs and Hair Follicles
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Guards the head, shields the eyes (eyelashes)
keep foreign particles out of the respiratory
tract (nose hairs)
A hair is produced by a hair follicle
As the daughter cells are pushed away from
the growing region they become keratinized
and die.
root - part of the hair enclosed in the follicle
Shaft - projecting from the surface of
scalp/skin
hair bulb matrix - the growth zone at the
inferior end of the follicle
medulla - a central core surrounded by a
bulky cortex layer
cuticle - single layer of cells overlap
 most heavily keratinized region
dermal sheath - dermal connective tissue
provides blood to hair bulb.
arrector pili - smooth muscle connecting hair
follicle to dermal tissue (goose bumps)
Accessory Structures
 Types
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Vellus
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Covers most of the body
Intermediate
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of Hair
Covers arms and legs
Terminal
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Covers the head
Accessory Structures
 Functions
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Protection from UV light
Insulation
Guards entrance to nose and ears
Movement of the hair sends impulses via
nerves to the brain
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of Hair
Such as when a bug is crawling on your arm
Contraction of the arrector pili muscles
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Results in goose bumps
Accessory Structures
 Hair
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color
Due to:
Variation in melanin production by the melanocytes
 Melanin production decreases with age
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Influenced by:
Genetics
 Hormones
 Environmental factors
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Hair growth
Active phase
Regression
phase
Resting phase
Reactivation
phase
Accessory Structures
• Nails
• Function
• Provide protection for the tips of the fingers and toes
• Structure
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Free edge
Lateral nail fold
Lunula
Eponychium
Hyponychium
Hyponychium
nails
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A scalelike modification of the epidermis
free edge
body (visible attached portion)
root (embedded in the skin)
Nailfolds - overlapped skin folds
cuticle - thick proximal nail fold
nail bed - stratum basale beneath the nail
nail matrix - thickened proximal area is responsible for nail growth
produced by the matrix nails become keratinized and die (nonliving)
Nails look pink because of the rich blood supply in the underlying dermis
Lunula - white crescent over nail matrix
Aging and the Integumentary System
 Epidermis
becomes thinner
 Dermis becomes thinner
 Number of Langerhans’ cells decreases
 Vitamin D production declines
 Melanocyte activity declines
 Glandular activity declines
 Hair follicles stop functioning
 Skin repair slows down
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eyelopmental Aspects of Skin l/and Body Membranes
During the fifth and sixth months of fetal development, the soon-to-be-born infant is covered with a downy type of hair called lanugo
(lah-noo'go), but this hairy cloak has usually been shed by birth. When a baby is born, its skin is covered with vernix caseosa (ver'niks
kah-se-o'sah). This white, cheesy-looking substance, produced by the sebaceous glands, protects the baby's skin while it is floating in its
water-filled sac inside the mother. The newborn's skin is very thin, and blood vessels can easily be seen through it. Commonly, there are
accumulations in the sebaceous glands, which appear as small white spots called milia (mil'e-ah), on the baby's nose and forehead.
These normally disappear by the third week after birth. As the baby grows, its skin becomes thicker and moist, and more subcutaneous
tat is deposited.
During adolescence, the skin and hair become ,,more oily as sebaceous glands are activated, and acne may appear. Acne usually
subsides in early adulthood, and the skin reaches its optimal appearance when we are in our 20s and 30s. Then visible changes in the
skin begin to appear as it is continually assaulted by abrasion, chemicals, wind, sun, and other irritants and as its pores become clogged
with air pollutants and bacteria. As a result, pimples, scales, and various kinds of dermatitis (der"mah-ti'tis), or skin inflammation, become more common.
During old age, the amount of subcutaneous tissue decreases, leading to the intolerance to cold so common in the elderly. The skin also
becomes drier (because of decreased oil production and declining numbers of collagen fibers) and, as a result, it may become itchy and
bothersome. Thinning of the skin, another result of the aging process, makes it more susceptible to bruising and other types of injuries.
The decreasing elasticity of the skin, along with the loss of subcutaneous fat, allows bags to form under our eyes, and our jowls begin to
sag. This loss of elasticity is speeded up by sunlight, so one of the best things you can do for your skin is to shield it from the sun by
wearing sunscreens and protective clothing. In doing so, you will also be decreasing the chance of skin cancer. Although there is no way
to avoid the aging of the skin, good nutrition, plenty of fluids, and cleanliness help delay the process.
Hair loses its luster as we age, and by age 50 the number of hair follicles has dropped by one-third and continues to decline, resulting in
hair thinning and some degree of baldness, or alopecia (al"o-pe'she-ah), in most people. Many men become obviously bald as they age,
a phenomenon called male pattern baldness. A bald man is not really hairless— he does have hairs in the bald area. But because those
hair follicles have begun to degenerate, the hairs are colorless and very tiny (and may not even emerge from the follicle). Such hairs are
called vellus (veil = wool) hairs. Another phenomenon of aging is graying hair. Like balding, this is usually genetically controlled by a
"delayed-action" gene. Once the gene takes effect, the amount of melanin deposited in the hair decreases or becomes entirely absent,
which results in gray-to-white hair.
S Certain events can cause hair to gray or fall out prematurely. For example, many people have claimed that they turned gray nearly
overnight because of some emotional crisis in their life. In addition, we know that anxiety, protein-deficient diets, therapy with certain
chemicals (chemotherapy), radiation, excessive vitamin A, and certain fungal diseases (ringworm) can cause both graying and hair loss.
However, when the cause of these conditions is not genetic, hair loss is usually not permanent. •