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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.
2. accessory structures (located in the dermis)
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hair, nails, exocrine glands, blood vessels,
sensory receptors for touch, pressure,
temperature, and pain
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Deep to the dermis, the loose connective tissue of the
subcutaneous layer /superficial fascia/ hypodermis, separates
the integument from the deep fascia around other organs
functions of the skin
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Protection of organs against shocks, abrasion, and
chemical attack.(stratified squamous epithelium)
Excretion of salts, water, and organic wastes by
glands.
Maintenance of temperature through insulation or
evaporation
Synthesis of vitamin D3 steroid converted to hormone
calcitriol, important to normal calcium metabolism.
Storage of nutrients.lipids
Detection of touch, pressure, pain, and temperature
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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Forms epidermal ridges, which extend into the dermis,
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, 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.
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keratinocytes the body's most
abundant epithelial cells form several
layers.
thick skin, on the palms and soles have
five layers
thin skin has only four layers
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.
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
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
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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yellow to brown to black, is produced by melanocytes
sunlight stimulates the melanocytes to produce more melanin
(tanning)
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basale cells phagocytize the melanin & forms a protective "umbrella"
over nuclei (DNA) from ultraviolet radiation in sunlight.
Freckles and moles are where melanin is concentrated in one
spot.
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excessive sun eventually damages the skin.
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It causes the elastic fibers to clump, leading to leathery skin. It
also depresses the immune system.
herpes simplex cold sore virus - are more likely to have
an eruption after sunbathing.
Overexposure to the sun can also alter the DNA of skin
cells and in this way lead to skin cancer.
Hairs and Hair Follicles
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millions of hairs all over the body
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
root - part of the hair enclosed in the follicle
Shaft - projecting from the surface of scalp or
skin
hair bulb matrix - the growth zone at the
inferior end of the follicle
As the daughter cells are pushed away from the
growing region they become keratinized and die.
medulla - a central core surrounded by a bulky
cortex layer
cuticle - single layer of cells overlap like roof
shingles
 most heavily keratinized region
pigment is made by melanocytes in hair bulb
dermal sheath - dermal connective tissue
provides blood to hair bulb.
arrector pili - smooth muscle connecting hair
follicle to dermal tissue (goose bumps)
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
glands of the Skin
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Cutaneous Glands (all are exocrine glands)
Exocrine Glands - release secretions to
surface via ducts
two groups:
1. sebaceous glands and
2. sweat glands.
Both formed by stratum basale & push into
dermis.
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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
Whitehead - a sebaceous gland's duct becomes blocked
by sebum
blackhead - the accumulated material oxidizes, dries and
darkens
Acne - active infection of the sebaceous glands
 can be mild or extremely severe, leading to permanent
scarring.
Seborrhea ("cradle cap“) in infants –
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overactivity of the sebaceous glands on the scalp
starts as pink, raised lesions that gradually form a yellow to brown
crust that sloughs off as oily dandruff.
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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
larger than eccrine glands, their ducts empty into hair follicles.
Their secretion contains fatty acids, proteins, salt & water
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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.
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Their precise function is not yet known, but they are activated by nerve
fibers during pain and stress and during sexual foreplay.
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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. •